LTC2288/LTC2287/LTC2286
1
228876f
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
Integrated Dual 10-Bit ADCs
Sample Rate: 65Msps/40Msps/25Msps
Single 3V Supply (2.7V to 3.4V)
Low Power: 400mW/235mW/150mW
61.6dB SNR at 70MHz Input
85dB SFDR at 70MHz Input
110dB Channel Isolation at 100MHz
Multiplexed or Separate Data Bus
Flexible Input: 1V
P-P
to 2V
P-P
Range
575MHz Full Power Bandwidth S/H
Clock Duty Cycle Stabilizer
Shutdown and Nap Modes
Pin Compatible Family
80Msps: LTC2294 (12-Bit), LTC2289 (10-Bit)
65Msps: LTC2293 (12-Bit), LTC2288 (10-Bit)
40Msps: LTC2292 (12-Bit), LTC2287 (10-Bit)
25Msps: LTC2291 (12-Bit), LTC2286 (10-Bit)
64-Pin (9mm 9mm) QFN Package
Dual 10-Bit, 65/40/25Msps
Low Noise 3V ADCs
The LTC
2288/LTC2287/LTC2286 are 10-bit 65Msps/
40Msps/25Msps, low noise dual 3V A/D converters de-
signed for digitizing high frequency, wide dynamic range
signals. The LTC2288/LTC2287/LTC2286 are perfect for
demanding imaging and communications applications
with AC performance that includes 61.6dB SNR and 85dB
SFDR for signals well beyond the Nyquist frequency.
DC specs include 0.1LSB INL (typ), 0.05LSB DNL (typ)
and 0.6 LSB INL, 0.5 LSB DNL over temperature. The
transition noise is a low 0.07LSB
RMS
.
A single 3V supply allows low power operation. A separate
output supply allows the outputs to drive 0.5V to 3.3V
logic. An optional multiplexer allows both channels to
share one digital output bus.
A single-ended CLK input controls converter operation. An
optional clock duty cycle stabilizer allows high perfor-
mance at full speed for a wide range of clock duty cycles.
LTC2288: SNR vs Input Frequency,
1dB, 2V Range, 65Msps
+
INPUT
S/H
ANALOG
INPUT A
ANALOG
INPUT B
CLK A
CLK B
10-BIT
PIPELINED
ADC CORE
CLOCK/DUTY CYCLE
CONTROL
OUTPUT
DRIVERS
OV
DD
OGND
MUX
D9A
D0A
OV
DD
OGND
228876 TA01
D9B
D0B
+
OUTPUT
DRIVERS
INPUT
S/H
10-BIT
PIPELINED
ADC CORE
CLOCK/DUTY CYCLE
CONTROL
INPUT FREQUENCY (MHz)
0
SNR (dBFS) 59.5
60.5
200
228876 TA02
58.5
57.5
50
100
150
62.5
61.5
Wireless and Wired Broadband Communication
Imaging Systems
Spectral Analysis
Portable Instrumentation
LTC2288/LTC2287/LTC2286
2
228876f
TOP VIEW
UP PACKAGE
64-LEAD (9mm
9mm) PLASTIC QFN
T
JMAX
= 125
C,
JA
= 20
C/W
EXPOSED PAD (PIN 65) IS GND AND MUST BE SOLDERED TO PCB
A
INA
+
1
A
INA
2
REFHA 3
REFHA 4
REFLA 5
REFLA 6
V
DD
7
CLKA
8
CLKB 9
V
DD
10
REFLB 11
REFLB 12
REFHB 13
REFHB 14
A
INB
15
A
INB
+
16
48 DA3
47 DA2
46 DA1
45 DA0
44 NC
43 NC
42 NC
41 NC
40 OFB
39 DB9
38 DB8
37 DB7
36 DB6
35 DB5
34 DB4
33 DB3
65
64 GND
63 V
DD
62 SENSEA
61 VCMA
60 MODE
59 SHDNA
58 OEA
57 OFA
56 DA9
55 DA8
54 DA7
53 DA6
52 DA5
51 DA4
50 OGND
49 OV
DD
GND
17
V
DD
18
SENSEB
19
VCMB
20
MUX 21
SHDNB 22
OEB 23
NC 24
NC 25
NC 26
NC 27
DB0 28
DB1 29
DB2 30
OGND 31
OV
DD
32
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
OV
DD
= V
DD
(Notes 1, 2)
Supply Voltage (V
DD
) ................................................. 4V
Digital Output Ground Voltage (OGND) ....... 0.3V to 1V
Analog Input Voltage (Note 3) ..... 0.3V to (V
DD
+ 0.3V)
Digital Input Voltage .................... 0.3V to (V
DD
+ 0.3V)
Digital Output Voltage ................ 0.3V to (OV
DD
+ 0.3V)
Power Dissipation ............................................ 1500mW
Operating Temperature Range
LTC2288C, LTC2287C, LTC2286C ........... 0C to 70C
LTC2288I, LTC2287I, LTC2286I ..........40C to 85C
Storage Temperature Range ..................65C to 125C
Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART
NUMBER
QFN PART*
MARKING
LTC2288UP
LTC2287UP
LTC2286UP
LTC2288CUP
LTC2288IUP
LTC2287CUP
LTC2287IUP
LTC2286CUP
LTC2286IUP
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature grade is identified by a label on the shipping container.
The
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. (Note 4)
LTC2288
LTC2287
LTC2286
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Resolution
10
10
10
Bits
(No Missing Codes)
Integral Linearity Error Differential Analog Input (Note 5)
0.6
0.1
0.6
0.6
0.1
0.6
0.6
0.1
0.6
LSB
Differential
Differential Analog Input
0.5
0.05
0.5
0.5
0.05
0.5
0.5
0.05
0.5
LSB
Linearity Error
Offset Error
(Note 6)
12
2
12
12
2
12
12
2
12
mV
Gain Error
External Reference
2.5
0.5
2.5
2.5
0.5
2.5
2.5
0.5
2.5
%FS
Offset Drift
10
10
10
V/C
Full-Scale Drift
Internal Reference
30
30
30
ppm/C
External Reference
15
15
15
ppm/C
Gain Matching
External Reference
0.3
0.3
0.3
%FS
Offset Matching
2
2
2
mV
Transition Noise
SENSE = 1V
0.07
0.07
0.07
LSB
RMS
CO VERTER CHARACTERISTICS
U
LTC2288/LTC2287/LTC2286
3
228876f
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Analog Input Range (A
IN
+
A
IN
)
2.7V < V
DD
< 3.4V (Note 7)
1V to 2V
V
V
IN,CM
Analog Input Common Mode
Differential Input (Note 7)
1
1.5
1.9
V
I
IN
Analog Input Leakage Current
0V < A
IN
+
, A
IN
< V
DD
1
1
A
I
SENSE
SENSEA, SENSEB Input Leakage
0V < SENSEA, SENSEB < 1V
3
3
A
I
MODE
MODE Input Leakage Current
0V < MODE < V
DD
3
3
A
t
AP
Sample-and-Hold Acquisition Delay Time
0
ns
t
JITTER
Sample-and-Hold Acquisition Delay Time Jitter
0.2
ps
RMS
CMRR
Analog Input Common Mode Rejection Ratio
80
dB
Full Power Bandwidth
Figure 8 Test Circuit
575
MHz
The
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25C. A
IN
= 1dBFS. (Note 4)
LTC2288
LTC2287
LTC2286
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
SNR
Signal-to-Noise Ratio
5MHz Input
61.8
61.8
61.8
dB
12.5MHz Input
60
61.8
dB
20MHz Input
60
61.8
dB
30MHz Input
60
61.8
dB
70MHz Input
61.7
61.7
61.6
dB
140MHz Input
61.6
61.6
61.6
dB
SFDR
5MHz Input
85
85
85
dB
12.5MHz Input
69
85
dB
20MHz Input
69
85
dB
30MHz Input
69
85
dB
70MHz Input
85
85
85
dB
140MHz Input
80
80
80
dB
SFDR
5MHz Input
85
85
85
dB
12.5MHz Input
74
85
dB
20MHz Input
74
85
dB
30MHz Input
74
85
dB
70MHz Input
85
85
85
dB
140MHz Input
85
85
85
dB
S/(N+D)
5MHz Input
61.8
61.8
61.8
dB
12.5MHz Input
60
61.8
dB
20MHz Input
60
61.7
dB
30MHz Input
60
61.8
dB
70MHz Input
61.7
61.6
61.6
dB
140MHz Input
61.6
61.6
61.5
dB
I
MD
f
IN
= Nyquist,
85
85
85
dB
Nyquist + 1MHz
Crosstalk
f
IN
= Nyquist
110
110
110
dB
A ALOG I PUT
U
U
DY
A
IC ACCURACY
U
W
The
denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25C. (Note 4)
Signal-to-Noise
Plus Distortion
Ratio
Intermodulation
Distortion
Spurious Free
Dynamic Range
4th Harmonic
or Higher
Spurious Free
Dynamic Range
2nd or 3rd
Harmonic
LTC2288/LTC2287/LTC2286
4
228876f
DIGITAL I PUTS A D DIGITAL OUTPUTS
U
U
The
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25C. (Note 4)
I TER AL REFERE CE CHARACTERISTICS
U
U
U
(Note 4)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CM
Output Voltage
I
OUT
= 0
1.475
1.500
1.525
V
V
CM
Output Tempco
30
ppm/C
V
CM
Line Regulation
2.7V < V
DD
< 3.3V
3
mV/V
V
CM
Output Resistance
1mA < I
OUT
< 1mA
4
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LOGIC INPUTS (CLK, OE, SHDN, MUX)
V
IH
High Level Input Voltage
V
DD
= 3V
2
V
V
IL
Low Level Input Voltage
V
DD
= 3V
0.8
V
I
IN
Input Current
V
IN
= 0V to V
DD
10
10
A
C
IN
Input Capacitance
(Note 7)
3
pF
LOGIC OUTPUTS
OV
DD
= 3V
C
OZ
Hi-Z Output Capacitance
OE = High (Note 7)
3
pF
I
SOURCE
Output Source Current
V
OUT
= 0V
50
mA
I
SINK
Output Sink Current
V
OUT
= 3V
50
mA
V
OH
High Level Output Voltage
I
O
= 10A
2.995
V
I
O
= 200A
2.7
2.99
V
V
OL
Low Level Output Voltage
I
O
= 10A
0.005
V
I
O
= 1.6mA
0.09
0.4
V
OV
DD
= 2.5V
V
OH
High Level Output Voltage
I
O
= 200A
2.49
V
V
OL
Low Level Output Voltage
I
O
= 1.6mA
0.09
V
OV
DD
= 1.8V
V
OH
High Level Output Voltage
I
O
= 200A
1.79
V
V
OL
Low Level Output Voltage
I
O
= 1.6mA
0.09
V
LTC2288/LTC2287/LTC2286
5
228876f
POWER REQUIRE E TS
W
U
The
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25C. (Note 8)
TI I G CHARACTERISTICS
U
W
The
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25C. (Note 4)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All voltage values are with respect to ground with GND and OGND
wired together (unless otherwise noted).
Note 3: When these pin voltages are taken below GND or above V
DD
, they
will be clamped by internal diodes. This product can handle input currents
of greater than 100mA below GND or above V
DD
without latchup.
Note 4: V
DD
= 3V, f
SAMPLE
= 65MHz (LTC2288), 40MHz (LTC2287), or
25MHz (LTC2286), input range = 2V
P-P
with differential drive, unless
otherwise noted.
Note 5: Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 6: Offset error is the offset voltage measured from 0.5 LSB when
the output code flickers between 00 0000 0000 and 11 1111 1111.
Note 7: Guaranteed by design, not subject to test.
Note 8: V
DD
= 3V, f
SAMPLE
= 65MHz (LTC2288), 40MHz (LTC2287), or
25MHz (LTC2286), input range = 1V
P-P
with differential drive. The supply
current and power dissipation are the sum total for both channels with
both channels active.
Note 9: Recommended operating conditions.
LTC2288
LTC2287
LTC2286
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
V
DD
Analog Supply
(Note 9)
2.7
3
3.4
2.7
3
3.4
2.7
3
3.4
V
Voltage
OV
DD
Output Supply
(Note 9)
0.5
3
3.6
0.5
3
3.6
0.5
3
3.6
V
Voltage
IV
DD
Supply Current
Both ADCs at f
S(MAX)
133
150
78
95
50
60
mA
P
DISS
Power Dissipation
Both ADCs at f
S(MAX)
400
450
235
285
150
180
mW
P
SHDN
Shutdown Power
SHDN = H,
2
2
2
mW
(Each Channel)
OE = H, No CLK
P
NAP
Nap Mode Power
SHDN = H,
15
15
15
mW
(Each Channel)
OE = L, No CLK
LTC2288
LTC2287
LTC2286
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
f
s
Sampling Frequency (Note 9)
1
65
1
40
1
25
MHz
t
L
CLK Low Time
Duty Cycle Stabilizer Off
7.3
7.7
500
11.8
12.5
500
18.9
20
500
ns
Duty Cycle Stabilizer On
5
7.7
500
5
12.5
500
5
20
500
ns
(Note 7)
t
H
CLK High Time
Duty Cycle Stabilizer Off
7.3
7.7
500
11.8
12.5
500
18.9
20
500
ns
Duty Cycle Stabilizer On
5
7.7
500
5
12.5
500
5
20
500
ns
(Note 7)
t
AP
Sample-and-Hold
0
0
0
ns
Aperture Delay
t
D
CLK to DATA Delay
C
L
= 5pF (Note 7)
1.4
2.7
5.4
1.4
2.7
5.4
1.4
2.7
5.4
ns
t
MD
MUX to DATA Delay C
L
= 5pF (Note 7)
1.4
2.7
5.4
1.4
2.7
5.4
1.4
2.7
5.4
ns
Data Access Time
C
L
= 5pF (Note 7)
4.3
10
4.3
10
4.3
10
ns
After OE
BUS Relinquish Time (Note 7)
3.3
8.5
3.3
8.5
3.3
8.5
ns
Pipeline
6
6
6
Cycles
Latency
LTC2288/LTC2287/LTC2286
6
228876f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LTC2288: Typical INL,
2V Range, 65Msps
LTC2288: Typical DNL,
2V Range, 65Msps
LTC2288: 8192 Point FFT,
f
IN
= 5MHz, 1dB, 2V Range,
65Msps
LTC2288: 8192 Point FFT,
f
IN
= 30MHz, 1dB, 2V Range,
65Msps
LTC2288: 8192 Point FFT,
f
IN
= 70MHz, 1dB, 2V Range,
65Msps
LTC2288: 8192 Point FFT,
f
IN
= 140MHz, 1dB, 2V Range,
65Msps
LTC2288: Grounded Input
Histogram, 65Msps
LTC2288/LTC2287/LTC2286:
Crosstalk vs Input Frequency
INPUT FREQUENCY (MHz)
0
130
CROSSTALK (dB)
125
120
115
110
105
100
20
40
60
80
228876 G01
100
CODE
0
INL ERROR (LSB)
0
0.25
0.50
1024
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
228876 G02
CODE
0
DNL ERROR (LSB)
0
0.25
0.50
1024
22876 G03
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
10
20
25
228876 G04
100
110
40
60
90
30
120
50
70
5
15
30
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
10
20
25
228876 G05
100
110
40
60
90
30
120
50
70
5
15
30
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
10
20
25
228876 G06
100
110
40
60
90
30
120
50
70
5
15
30
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
10
20
25
228876 G07
100
110
40
60
90
30
120
50
70
5
15
30
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
10
20
25
228876 G08
100
110
40
60
90
30
120
50
70
5
15
30
CODE
70000
60000
50000
40000
30000
20000
10000
0
512
65520
513
228876 G09
511
0
0
COUNT
LTC2288: 8192 Point 2-Tone FFT,
f
IN
= 28.2MHz and 26.8MHz,
1dB, 2V Range 65Msps
LTC2288/LTC2287/LTC2286
7
228876f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LTC2288: SNR and SFDR vs
Sample Rate, 2V Range,
f
IN
= 5MHz, 1dB
LTC2288: SNR vs Input Level,
f
IN
= 30MHz, 2V Range, 65Msps
LTC2288: I
OVDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB,
O
VDD
= 1.8V
LTC2288: I
VDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB
LTC2288: SFDR vs Input Level,
f
IN
= 30MHz, 2V Range, 65Msps
LTC2288: SFDR vs Input Frequency,
1dB, 2V Range, 65Msps
SAMPLE RATE (Msps)
I
VDD
(mA)
228876 G15
155
145
135
125
115
105
95
0
20
40
50
10
30
60
70
80
2V RANGE
1V RANGE
SAMPLE RATE (Msps)
I
OVDD
(mA)
228876 G16
12
10
8
6
4
2
0
0
20
40
50
10
30
60
70
80
LTC2288: SNR vs Input Frequency,
1dB, 2V Range, 65Msps
INPUT FREQUENCY (MHz)
0
SNR (dBFS) 59.5
60.5
200
228876 G10
58.5
57.5
50
100
150
62.5
61.5
INPUT FREQUENCY (MHz)
0
85
90
100
150
228876 G11
80
75
50
100
200
70
65
95
SFDR (dBFS)
SAMPLE RATE (Msps)
0
SNR AND SFDR (dBFS)
80
90
100
80
228876 G12
70
60
50
10 20 30 40 50 60 70
90 100 110
SFDR
SNR
INPUT LEVEL (dBFS)
60
SNR (dBc AND dBFS)
30
40
50
30
10
228876 G13
20
10
0
50
40
dBFS
dBc
20
60
70
80
0
INPUT LEVEL (dBFS)
60
0
SFDR (dBc AND dBFS)
20
40
60
80
120
50
40
30
dBFS
dBc
20
228876 G14
10
0
100
10
30
50
70
110
90
80dBc SFDR
REFERENCE LINE
LTC2288/LTC2287/LTC2286
8
228876f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LTC2287: 8192 Point FFT,
f
IN
= 30MHz, 1dB, 2V Range,
40Msps
LTC2287: 8192 Point FFT,
f
IN
= 70MHz, 1dB, 2V Range,
40Msps
LTC2287: 8192 Point FFT,
f
IN
= 140MHz, 1dB, 2V Range,
40Msps
LTC2287: 8192 Point 2-Tone FFT,
f
IN
= 21.6MHz and 23.6MHz,
1dB, 2V Range, 40Msps
LTC2287: Grounded Input
Histogram, 40Msps
LTC2287: SNR vs Input Frequency,
1dB, 2V Range, 40Msps
LTC2287: Typical INL,
2V Range, 40Msps
LTC2287: Typical DNL,
2V Range, 40Msps
LTC2287: 8192 Point FFT,
f
IN
= 5MHz, 1dB, 2V Range,
40Msps
CODE
0
INL ERROR (LSB)
0
0.25
0.50
1024
228876 G17
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
CODE
0
DNL ERROR (LSB)
0
0.25
0.50
1024
228876 G18
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
30
20
20
228876 G19
70
80
120
5
10
15
100
0
10
40
50
90
110
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
30
20
20
228876 G20
70
80
120
5
10
15
100
0
10
40
50
90
110
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
30
20
20
228876 G21
70
80
120
5
10
15
100
0
10
40
50
90
110
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
30
20
20
228876 G22
70
80
120
5
10
15
100
0
10
40
50
90
110
FREQUENCY (MHz)
0
AMPLITUDE (dB)
60
30
20
20
228876 G23
70
80
120
5
10
15
100
0
10
40
50
90
110
CODE
70000
60000
50000
40000
30000
20000
10000
0
511
65520
512
228876 G24
510
0
0
COUNT
INPUT FREQUENCY (MHz)
0
SNR (dBFS) 59.5
60.5
200
228876 G25
58.5
57.5
50
100
150
62.5
61.5
LTC2288/LTC2287/LTC2286
9
228876f
LTC2287: I
OVDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB,
O
VDD
= 1.8V
LTC2287: I
VDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LTC2287: SFDR vs Input Level,
f
IN
= 5MHz, 2V Range, 40Msps
LTC2286: Typical INL,
2V Range, 25Msps
LTC2286: Typical DNL,
2V Range, 25Msps
LTC2286: 8192 Point FFT,
f
IN
= 5MHz, 1dB, 2V Range,
25Msps
LTC2287: SFDR vs Input Frequency,
1dB, 2V Range, 40Msps
LTC2287: SNR and SFDR vs
Sample Rate, 2V Range,
f
IN
= 5MHz, 1dB
LTC2287: SNR vs Input Level,
f
IN
= 5MHz, 2V Range, 40Msps
SAMPLE RATE (Msps)
0
I
VDD
(mA)
40
228876 G30
10
20
30
50
100
90
80
70
60
2V RANGE
1V RANGE
SAMPLE RATE (Msps)
0
I
OVDD
(mA)
4
6
40
228876 G31
2
0
10
20
30
50
8
INPUT FREQUENCY (MHz)
0
85
90
100
150
228876 G26
80
75
50
100
200
70
65
95
SFDR (dBFS)
SAMPLE RATE (Msps)
0
SNR AND SFDR (dBFS)
80
90
100
80
228876 G27
70
60
50
10
20
30
40
50
60
70
SFDR
SNR
INPUT LEVEL (dBFS)
60
SNR (dBc AND dBFS)
30
40
50
30
10
228876 G28
20
10
0
50
40
dBFS
dBc
20
60
70
80
0
INPUT LEVEL (dBFS)
60
0
SFDR (dBc AND dBFS)
20
40
60
80
120
50
40
30
dBFS
dBc
20
228876 G29
10
0
100
10
30
50
70
110
90
80dBc SFDR
REFERENCE LINE
CODE
0
INL ERROR (LSB)
0
0.25
0.50
1024
228876 G32
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
CODE
0
DNL ERROR (LSB)
0
0.25
0.50
1024
228876 G33
0.25
0.50
1.00
256
512
768
0.75
1.00
0.75
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
4
8
10
228876 G34
100
110
40
60
90
30
120
50
70
2
6
12
LTC2288/LTC2287/LTC2286
10
228876f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
LTC2286: 8192 Point 2-Tone FFT,
f
IN
= 10.9MHz and 13.8MHz,
1dB, 2V Range, 25Msps
LTC2286: Grounded Input
Histogram, 25Msps
LTC2286: SNR vs Input Frequency,
1dB, 2V Range, 25Msps
LTC2286: SFDR vs Input
Frequency, 1dB, 2V Range,
25Msps
LTC2286: SNR and SFDR vs
Sample Rate, 2V Range,
f
IN
= 5MHz, 1dB
LTC2286: SNR vs Input Level,
f
IN
= 5MHz, 2V Range, 25Msps
LTC2286: 8192 Point FFT,
f
IN
= 30MHz, 1dB, 2V Range,
25Msps
LTC2286: 8192 Point FFT,
f
IN
= 70MHz, 1dB, 2V Range,
25Msps
LTC2286: 8192 Point FFT,
f
IN
= 140MHz, 1dB, 2V Range,
25Msps
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
4
8
10
228876 G35
100
110
40
60
90
30
120
50
70
2
6
12
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
4
8
10
228876 G36
100
110
40
60
90
30
120
50
70
2
6
12
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
4
8
10
228876 G37
100
110
40
60
90
30
120
50
70
2
6
12
FREQUENCY (MHz)
0
AMPLITUDE (dB) 80
20
10
0
4
8
10
228876 G38
100
110
40
60
90
30
120
50
70
2
6
12
CODE
70000
60000
50000
40000
30000
20000
10000
0
512
65520
513
228876 G39
511
0
0
COUNT
INPUT FREQUENCY (MHz)
0
SNR (dBFS) 59.5
60.5
200
228876 G40
58.5
57.5
50
100
150
62.5
61.5
INPUT FREQUENCY (MHz)
0
85
90
100
150
228876 G41
80
75
50
100
200
70
65
95
SFDR (dBFS)
SAMPLE RATE (Msps)
0
SNR AND SFDR (dBFS)
80
90
100
40
228876 G42
70
60
50
5
10 15 20 25 30 35
45 50
SFDR
SNR
INPUT LEVEL (dBFS)
60
SNR (dBc AND dBFS)
30
40
50
30
10
228876 G43
20
10
0
50
40
dBFS
dBc
20
60
70
80
0
LTC2288/LTC2287/LTC2286
11
228876f
U
U
U
PI FU CTIO S
A
INA
+
(Pin 1): Channel A Positive Differential Analog
Input.
A
INA
(Pin 2): Channel A Negative Differential Analog
Input.
REFHA (Pins 3, 4): Channel A High Reference. Short
together and bypass to Pins 5, 6 with a 0.1F ceramic chip
capacitor as close to the pin as possible. Also bypass to
Pins 5, 6 with an additional 2.2F ceramic chip capacitor
and to ground with a 1F ceramic chip capacitor.
REFLA (Pins 5, 6): Channel A Low Reference. Short
together and bypass to Pins 3, 4 with a 0.1F ceramic chip
capacitor as close to the pin as possible. Also bypass to
Pins 3, 4 with an additional 2.2F ceramic chip capacitor
and to ground with a 1F ceramic chip capacitor.
V
DD
(Pins 7, 10, 18, 63): Analog 3V Supply. Bypass to
GND with 0.1F ceramic chip capacitors.
CLKA (Pin 8): Channel A Clock Input. The input sample
starts on the positive edge.
CLKB (Pin 9): Channel B Clock Input. The input sample
starts on the positive edge.
REFLB (Pins 11, 12): Channel B Low Reference. Short
together and bypass to Pins 13, 14 with a 0.1F ceramic
chip capacitor as close to the pin as possible. Also bypass
to Pins 13, 14 with an additional 2.2F ceramic chip ca-
pacitor and to ground with a 1F ceramic chip capacitor.
REFHB (Pins 13, 14): Channel B High Reference. Short
together and bypass to Pins 11, 12 with a 0.1F ceramic
chip capacitor as close to the pin as possible. Also bypass
to Pins 11, 12 with an additional 2.2F ceramic chip ca-
pacitor and to ground with a 1F ceramic chip capacitor.
A
INB
(Pin 15): Channel B Negative Differential Analog
Input.
A
INB
+
(Pin 16): Channel B Positive Differential Analog
Input.
GND (Pins 17, 64): ADC Power Ground.
SENSEB (Pin 19): Channel B Reference Programming Pin.
Connecting SENSEB to V
CMB
selects the internal reference
and a 0.5V input range. V
DD
selects the internal reference
and a 1V input range. An external reference greater than
0.5V and less than 1V applied to SENSEB selects an input
range of V
SENSEB
. 1V is the largest valid input range.
V
CMB
(Pin 20): Channel B 1.5V Output and Input Common
Mode Bias. Bypass to ground with 2.2F ceramic chip
capacitor. Do not connect to V
CMA
.
LTC2286: I
OVDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB,
O
VDD
= 1.8V
LTC2286: I
VDD
vs Sample Rate,
5MHz Sine Wave Input, 1dB
LTC2286: SFDR vs Input Level,
f
IN
= 5MHz, 2V Range, 25Msps
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
SAMPLE RATE (Msps)
I
VDD
(mA)
228876 G45
70
60
50
40
30
0
10
20
5
15
25
30
35
2V RANGE
1V RANGE
0
10
20
5
15
25
30
35
SAMPLE RATE (Msps)
I
OVDD
(mA)
228876 G46
6
4
2
0
INPUT LEVEL (dBFS)
60
0
SFDR (dBc AND dBFS)
20
40
60
80
120
50
40
30
dBFS
dBc
20
228876 G44
10
0
100
10
30
50
70
110
90
80dBc SFDR
REFERENCE LINE
LTC2288/LTC2287/LTC2286
12
228876f
MUX (Pin 21): Digital Output Multiplexer Control. If MUX
is High, Channel A comes out on DA0-DA13, OFA; Channel B
comes out on DB0-DB13, OFB. If MUX is Low, the output
busses are swapped and Channel A comes out on DB0-
DB13, OFB; Channel B comes out on DA0-DA13, OFA. To
multiplex both channels onto a single output bus, connect
MUX, CLKA and CLKB together.
SHDNB (Pin 22): Channel B Shutdown Mode Selection
Pin. Connecting SHDNB to GND and OEB to GND results
in normal operation with the outputs enabled. Connecting
SHDNB to GND and OEB to V
DD
results in normal opera-
tion with the outputs at high impedance. Connecting
SHDNB to V
DD
and OEB to GND results in nap mode with
the outputs at high impedance. Connecting SHDNB to V
DD
and OEB to V
DD
results in sleep mode with the outputs at
high impedance.
OEB (Pin 23): Channel B Output Enable Pin. Refer to
SHDNB pin function.
NC (Pins 24 to 27, 41 to 44): Do Not Connect These Pins.
DB0 DB9 (Pins 28 to 30, 33 to 39): Channel B Digital
Outputs. DB9 is the MSB.
OGND (Pins 31, 50): Output Driver Ground.
OV
DD
(Pins 32, 49): Positive Supply for the Output Driv-
ers. Bypass to ground with 0.1F ceramic chip capacitor.
OFB (Pin 40): Channel B Overflow/Underflow Output.
High when an overflow or underflow has occurred.
DA0 DA9 (Pins 45 to 48, 51 to 56): Channel A Digital
Outputs. DA9 is the MSB.
OFA (Pin 57): Channel A Overflow/Underflow Output.
High when an overflow or underflow has occurred.
OEA (Pin 58): Channel A Output Enable Pin. Refer to
SHDNA pin function.
SHDNA (Pin 59): Channel A Shutdown Mode Selection
Pin. Connecting SHDNA to GND and OEA to GND results
in normal operation with the outputs enabled. Connecting
SHDNA to GND and OEA to V
DD
results in normal opera-
tion with the outputs at high impedance. Connecting
SHDNA to V
DD
and OEA to GND results in nap mode with
the outputs at high impedance. Connecting SHDNA to V
DD
and OEA to V
DD
results in sleep mode with the outputs at
high impedance.
MODE (Pin 60): Output Format and Clock Duty Cycle
Stabilizer Selection Pin. Note that MODE controls both
channels. Connecting MODE to GND selects straight bi-
nary output format and turns the clock duty cycle stabilizer
off. 1/3 V
DD
selects straight binary output format and turns
the clock duty cycle stabilizer on. 2/3 V
DD
selects 2's
complement output format and turns the clock duty cycle
stabilizer on. V
DD
selects 2's complement output format
and turns the clock duty cycle stabilizer off.
V
CMA
(Pin 61): Channel A 1.5V Output and Input Common
Mode Bias. Bypass to ground with 2.2F ceramic chip
capacitor. Do not connect to V
CMB
.
SENSEA (Pin 62): Channel A Reference Programming Pin.
Connecting SENSEA to V
CMA
selects the internal reference
and a 0.5V input range. V
DD
selects the internal reference
and a 1V input range. An external reference greater than
0.5V and less than 1V applied to SENSEA selects an input
range of V
SENSEA
. 1V is the largest valid input range.
GND (Exposed Pad) (Pin 65): ADC Power Ground. The
Exposed Pad on the bottom of the package needs to be
soldered to ground.
U
U
U
PI FU CTIO S
LTC2288/LTC2287/LTC2286
13
228876f
FU
N
CTIO
N
AL BLOCK DIAGRA
U
U
W
Figure 1. Functional Block Diagram (Only One Channel is Shown)
SHIFT REGISTER
AND CORRECTION
DIFF
REF
AMP
REF
BUF
2.2F
1F
1F
0.1F
INTERNAL CLOCK SIGNALS
REFH
REFL
CLOCK/DUTY
CYCLE
CONTROL
RANGE
SELECT
1.5V
REFERENCE
FIRST PIPELINED
ADC STAGE
FIFTH PIPELINED
ADC STAGE
SIXTH PIPELINED
ADC STAGE
FOURTH PIPELINED
ADC STAGE
SECOND PIPELINED
ADC STAGE
REFH
REFL
CLK
OE
MODE
OGND
OV
DD
228876 F01
INPUT
S/H
SENSE
V
CM
A
IN
A
IN
+
2.2F
THIRD PIPELINED
ADC STAGE
OUTPUT
DRIVERS
CONTROL
LOGIC
SHDN
OF
D9
D0
LTC2288/LTC2287/LTC2286
14
228876f
Dual Digital Output Bus Timing
(Only One Channel is Shown)
TI I G DIAGRA S
W
U
W
t
AP
N + 1
N + 2
N + 4
N + 3
N + 5
N
ANALOG
INPUT
t
H
t
D
t
L
N 5
N 4
N 3
N 2
CLK
D0-D9, OF
228876 TD01
N 6
N 1
Multiplexed Digital Output Bus Timing
t
APB
B + 1
B + 2
B + 4
B + 3
B
ANALOG
INPUT B
t
APA
A + 1
A 6
B 6
B 6
A 6
A 5
B 5
B 5
A 5
A 4
B 4
B 4
A 4
A 3
B 3
B 3
A 3
A 2
B 2
A + 2
A + 4
A + 3
A
ANALOG
INPUT A
t
H
t
D
t
MD
t
L
CLKA = CLKB = MUX
D0A-D9A, OFA
228876 TD02
D0B-D9B, OFB
LTC2288/LTC2287/LTC2286
15
228876f
DYNAMIC PERFORMANCE
Signal-to-Noise Plus Distortion Ratio
The signal-to-noise plus distortion ratio [S/(N + D)] is the
ratio between the RMS amplitude of the fundamental input
frequency and the RMS amplitude of all other frequency
components at the ADC output. The output is band limited
to frequencies above DC to below half the sampling
frequency.
Signal-to-Noise Ratio
The signal-to-noise ratio (SNR) is the ratio between the
RMS amplitude of the fundamental input frequency and
the RMS amplitude of all other frequency components
except the first five harmonics and DC.
Total Harmonic Distortion
Total harmonic distortion is the ratio of the RMS sum of all
harmonics of the input signal to the fundamental itself. The
out-of-band harmonics alias into the frequency band
between DC and half the sampling frequency. THD is
expressed as:
THD = 20Log (V2
2
+ V3
2
+ V4
2
+ . . . Vn
2
)/V1
where V1 is the RMS amplitude of the fundamental fre-
quency and V2 through Vn are the amplitudes of the
second through nth harmonics. The THD calculated in this
data sheet uses all the harmonics up to the fifth.
Intermodulation Distortion
If the ADC input signal consists of more than one spectral
component, the ADC transfer function nonlinearity can
produce intermodulation distortion (IMD) in addition to
THD. IMD is the change in one sinusoidal input caused by
the presence of another sinusoidal input at a different
frequency.
If two pure sine waves of frequencies fa and fb are applied
to the ADC input, nonlinearities in the ADC transfer func-
tion can create distortion products at the sum and differ-
ence frequencies of mfa nfb, where m and n = 0, 1, 2, 3,
etc. The 3rd order intermodulation products are 2fa + fb,
APPLICATIO S I FOR ATIO
W
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2fb + fa, 2fa fb and 2fb fa. The intermodulation
distortion is defined as the ratio of the RMS value of either
input tone to the RMS value of the largest 3rd order
intermodulation product.
Spurious Free Dynamic Range (SFDR)
Spurious free dynamic range is the peak harmonic or
spurious noise that is the largest spectral component
excluding the input signal and DC. This value is expressed
in decibels relative to the RMS value of a full scale input
signal.
Input Bandwidth
The input bandwidth is that input frequency at which the
amplitude of the reconstructed fundamental is reduced by
3dB for a full scale input signal.
Aperture Delay Time
The time from when CLK reaches midsupply to the instant
that the input signal is held by the sample and hold circuit.
Aperture Delay Jitter
The variation in the aperture delay time from conversion to
conversion. This random variation will result in noise
when sampling an AC input. The signal to noise ratio due
to the jitter alone will be:
SNR
JITTER
= 20log (2) f
IN
t
JITTER
Crosstalk
Crosstalk is the coupling from one channel (being driven
by a full-scale signal) onto the other channel (being driven
by a 1dBFS signal).
CONVERTER OPERATION
As shown in Figure 1, the LTC2288/LTC2287/LTC2286 are
dual CMOS pipelined multistep converters. The convert-
ers have six pipelined ADC stages; a sampled analog input
will result in a digitized value six cycles later (see the
Timing Diagram section). For optimal AC performance the
analog inputs should be driven differentially. For cost
LTC2288/LTC2287/LTC2286
16
228876f
sensitive applications, the analog inputs can be driven
single-ended with slightly worse harmonic distortion. The
CLK input is single-ended. The LTC2288/LTC2287/
LTC2286 have two phases of operation, determined by the
state of the CLK input pin.
Each pipelined stage shown in Figure 1 contains an ADC,
a reconstruction DAC and an interstage residue amplifier.
In operation, the ADC quantizes the input to the stage and
the quantized value is subtracted from the input by the
DAC to produce a residue. The residue is amplified and
output by the residue amplifier. Successive stages operate
out of phase so that when the odd stages are outputting
their residue, the even stages are acquiring that residue
and vice versa.
When CLK is low, the analog input is sampled differentially
directly onto the input sample-and-hold capacitors, inside
the "Input S/H" shown in the block diagram. At the instant
that CLK transitions from low to high, the sampled input is
held. While CLK is high, the held input voltage is buffered
by the S/H amplifier which drives the first pipelined ADC
stage. The first stage acquires the output of the S/H during
this high phase of CLK. When CLK goes back low, the first
stage produces its residue which is acquired by the
second stage. At the same time, the input S/H goes back
to acquiring the analog input. When CLK goes back high,
the second stage produces its residue which is acquired
by the third stage. An identical process is repeated for the
APPLICATIO S I FOR ATIO
W
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third, fourth and fifth stages, resulting in a fifth stage
residue that is sent to the sixth stage ADC for final
evaluation.
Each ADC stage following the first has additional range to
accommodate flash and amplifier offset errors. Results
from all of the ADC stages are digitally synchronized such
that the results can be properly combined in the correction
logic before being sent to the output buffer.
SAMPLE/HOLD OPERATION AND INPUT DRIVE
Sample/Hold Operation
Figure 2 shows an equivalent circuit for the LTC2288/
LTC2287/LTC2286 CMOS differential sample-and-hold.
The analog inputs are connected to the sampling capaci-
tors (C
SAMPLE
) through NMOS transistors. The capacitors
shown attached to each input (C
PARASITIC
) are the summa-
tion of all other capacitance associated with each input.
During the sample phase when CLK is low, the transistors
connect the analog inputs to the sampling capacitors and
they charge to and track the differential input voltage.
When CLK transitions from low to high, the sampled input
voltage is held on the sampling capacitors. During the hold
phase when CLK is high, the sampling capacitors are
disconnected from the input and the held voltage is passed
to the ADC core for processing. As CLK transitions from
high to low, the inputs are reconnected to the sampling
Figure 2. Equivalent Input Circuit
V
DD
V
DD
V
DD
15
15
C
PARASITIC
1pF
C
PARASITIC
1pF
C
SAMPLE
4pF
C
SAMPLE
4pF
LTC2288/LTC2287/LTC2286
A
IN
+
A
IN
CLK
228876 F02
LTC2288/LTC2287/LTC2286
17
228876f
capacitors to acquire a new sample. Since the sampling
capacitors still hold the previous sample, a charging glitch
proportional to the change in voltage between samples will
be seen at this time. If the change between the last sample
and the new sample is small, the charging glitch seen at
the input will be small. If the input change is large, such as
the change seen with input frequencies near Nyquist, then
a larger charging glitch will be seen.
Single-Ended Input
For cost sensitive applications, the analog inputs can be
driven single-ended. With a single-ended input the har-
monic distortion and INL will degrade, but the SNR and
DNL will remain unchanged. For a single-ended input, A
IN
+
should be driven with the input signal and A
IN
should be
connected to 1.5V or V
CM
.
Common Mode Bias
For optimal performance the analog inputs should be
driven differentially. Each input should swing 0.5V for
the 2V range or 0.25V for the 1V range, around a
common mode voltage of 1.5V. The V
CM
output pin may
be used to provide the common mode bias level. V
CM
can
be tied directly to the center tap of a transformer to set the
DC input level or as a reference level to an op amp
differential driver circuit. The V
CM
pin must be bypassed to
ground close to the ADC with a 2.2F or greater capacitor.
Input Drive Impedance
As with all high performance, high speed ADCs, the
dynamic performance of the LTC2288/LTC2287/LTC2286
can be influenced by the input drive circuitry, particularly
the second and third harmonics. Source impedance and
reactance can influence SFDR. At the falling edge of CLK,
the sample-and-hold circuit will connect the 4pF sampling
capacitor to the input pin and start the sampling period.
The sampling period ends when CLK rises, holding the
sampled input on the sampling capacitor. Ideally the input
circuitry should be fast enough to fully charge
the sampling capacitor during the sampling period
1/(2F
ENCODE
); however, this is not always possible and the
incomplete settling may degrade the SFDR. The sampling
APPLICATIO S I FOR ATIO
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glitch has been designed to be as linear as possible to
minimize the effects of incomplete settling.
For the best performance, it is recommended to have a
source impedance of 100 or less for each input. The
source impedance should be matched for the differential
inputs. Poor matching will result in higher even order
harmonics, especially the second.
Input Drive Circuits
Figure 3 shows the LTC2288/LTC2287/LTC2286 being
driven by an RF transformer with a center tapped second-
ary. The secondary center tap is DC biased with V
CM
,
setting the ADC input signal at its optimum DC level.
Terminating on the transformer secondary is desirable, as
this provides a common mode path for charging glitches
caused by the sample and hold. Figure 3 shows a 1:1 turns
ratio transformer. Other turns ratios can be used if the
source impedance seen by the ADC does not exceed 100
for each ADC input. A disadvantage of using a transformer
is the loss of low frequency response. Most small RF
transformers have poor performance at frequencies be-
low 1MHz.
Figure 3. Single-Ended to Differential Conversion
Using a Transformer
25
25
25
25
0.1F
A
IN
+
A
IN
12pF
2.2F
V
CM
LTC2288
LTC2287
LTC2286
ANALOG
INPUT
0.1F
T1
1:1
T1 = MA/COM ETC1-1T
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
228876 F03
Figure 4 demonstrates the use of a differential amplifier to
convert a single ended input signal into a differential input
signal. The advantage of this method is that it provides low
frequency input response; however, the limited gain band-
width of most op amps will limit the SFDR at high input
frequencies.
LTC2288/LTC2287/LTC2286
18
228876f
Figure 5 shows a single-ended input circuit. The imped-
ance seen by the analog inputs should be matched. This
circuit is not recommended if low distortion is required.
APPLICATIO S I FOR ATIO
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Figure 6. Recommended Front End Circuit for
Input Frequencies Between 70MHz and 170MHz
Figure 8. Recommended Front End Circuit for
Input Frequencies Above 300MHz
Figure 7. Recommended Front End Circuit for
Input Frequencies Between 170MHz and 300MHz
25
25
12
12
0.1F
A
IN
+
A
IN
8pF
2.2F
V
CM
ANALOG
INPUT
0.1F
0.1F
T1
T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
228876 F06
LTC2288
LTC2287
LTC2286
Figure 5. Single-Ended Drive
Figure 4. Differential Drive with an Amplifier
25
25
12pF
2.2F
V
CM
228876 F04
+
+
CM
ANALOG
INPUT
HIGH SPEED
DIFFERENTIAL
AMPLIFIER
A
IN
+
A
IN
LTC2288
LTC2287
LTC2286
25
0.1F
ANALOG
INPUT
V
CM
A
IN
+
A
IN
1k
12pF
228876 F05
2.2F
1k
25
0.1F
LTC2288
LTC2287
LTC2286
The 25 resistors and 12pF capacitor on the analog inputs
serve two purposes: isolating the drive circuitry from the
sample-and-hold charging glitches and limiting the
wideband noise at the converter input.
For input frequencies above 70MHz, the input circuits of
Figure 6, 7 and 8 are recommended. The balun trans-
former gives better high frequency response than a flux
coupled center tapped transformer. The coupling capaci-
tors allow the analog inputs to be DC biased at 1.5V. In
Figure 8, the series inductors are impedance matching
elements that maximize the ADC bandwidth.
25
25
0.1F
A
IN
+
A
IN
2.2F
V
CM
ANALOG
INPUT
0.1F
0.1F
T1
T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
228876 F07
LTC2288
LTC2287
LTC2286
25
25
0.1F
A
IN
+
A
IN
2.2F
V
CM
ANALOG
INPUT
0.1F
0.1F
T1
T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS, INDUCTORS
ARE 0402 PACKAGE SIZE
228876 F08
6.8nH
6.8nH
LTC2288
LTC2287
LTC2286
LTC2288/LTC2287/LTC2286
19
228876f
APPLICATIO S I FOR ATIO
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Reference Operation
Figure 9 shows the LTC2288/LTC2287/LTC2286 refer-
ence circuitry consisting of a 1.5V bandgap reference, a
difference amplifier and switching and control circuit. The
internal voltage reference can be configured for two pin
selectable input ranges of 2V (1V differential) or 1V
(0.5V differential). Tying the SENSE pin to V
DD
selects
the 2V range; tying the SENSE pin to V
CM
selects the 1V
range.
The 1.5V bandgap reference serves two functions: its
output provides a DC bias point for setting the common
mode voltage of any external input circuitry; additionally,
the reference is used with a difference amplifier to gener-
ate the differential reference levels needed by the internal
ADC circuitry. An external bypass capacitor is required for
the 1.5V reference output, V
CM
. This provides a high
frequency low impedance path to ground for internal and
external circuitry.
The difference amplifier generates the high and low refer-
ence for the ADC. High speed switching circuits are
connected to these outputs and they must be externally
bypassed. Each output has two pins. The multiple output
pins are needed to reduce package inductance. Bypass
capacitors must be connected as shown in Figure 9. Each
ADC channel has an independent reference with its own
bypass capacitors. The two channels can be used with the
same or different input ranges.
Other voltage ranges between the pin selectable ranges
can be programmed with two external resistors as shown
in Figure 10. An external reference can be used by applying
its output directly or through a resistor divider to SENSE.
It is not recommended to drive the SENSE pin with a logic
device. The SENSE pin should be tied to the appropriate
level as close to the converter as possible. If the SENSE pin
is driven externally, it should be bypassed to ground as
close to the device as possible with a 1F ceramic capacitor.
For the best channel matching, connect an external reference
to SENSEA and SENSEB.
Figure 10. 1.5V Range ADC
Figure 9. Equivalent Reference Circuit
V
CM
REFH
SENSE
TIE TO V
DD
FOR 2V RANGE;
TIE TO V
CM
FOR 1V RANGE;
RANGE = 2 V
SENSE
FOR
0.5V < V
SENSE
< 1V
1.5V
REFL
2.2F
2.2F
INTERNAL ADC
HIGH REFERENCE
BUFFER
0.1F
228876 F09
4
DIFF AMP
1F
1F
INTERNAL ADC
LOW REFERENCE
1.5V BANDGAP
REFERENCE
1V
0.5V
RANGE
DETECT
AND
CONTROL
LTC2288/LTC2287/LTC2286
V
CM
SENSE
1.5V
0.75V
2.2F
12k
1F
12k
228876 F10
LTC2288
LTC2287
LTC2286
Input Range
The input range can be set based on the application. The
2V input range will provide the best signal-to-noise perfor-
mance while maintaining excellent SFDR. The 1V input
range will have better SFDR performance, but the SNR will
degrade by 0.6dB. See the Typical Performance Charac-
teristics section.
Driving the Clock Input
The CLK inputs can be driven directly with a CMOS or TTL
level signal. A sinusoidal clock can also be used along with
a low jitter squaring circuit before the CLK pin (Figure 11).
LTC2288/LTC2287/LTC2286
20
228876f
APPLICATIO S I FOR ATIO
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The noise performance of the LTC2288/LTC2287/LTC2286
can depend on the clock signal quality as much as on the
analog input. Any noise present on the clock signal will
result in additional aperture jitter that will be RMS summed
with the inherent ADC aperture jitter.
In applications where jitter is critical, such as when digitiz-
ing high input frequencies, use as large an amplitude as
possible. Also, if the ADC is clocked with a sinusoidal
signal, filter the CLK signal to reduce wideband noise and
distortion products generated by the source.
It is recommended that CLKA and CLKB are shorted
together and driven by the same clock source. If a small
time delay is desired between when the two channels
sample the analog inputs, CLKA and CLKB can be driven
by two different signals. If this delay exceeds 1ns, the
performance of the part may degrade. CLKA and CLKB
should not be driven by asynchronous signals.
Maximum and Minimum Conversion Rates
The maximum conversion rate for the LTC2288/LTC2287/
LTC2286 is 65Msps (LTC2288), 40Msps (LTC2287), and
25Msps (LTC2286). For the ADC to operate properly, the
CLK signal should have a 50% (5%) duty cycle. Each half
cycle must have at least 7.3ns (LTC2288), 11.8ns
(LTC2287), and 18.9ns (LTC2286) for the ADC internal
circuitry to have enough settling time for proper operation.
An optional clock duty cycle stabilizer circuit can be used
if the input clock has a non 50% duty cycle. This circuit
uses the rising edge of the CLK pin to sample the analog
input. The falling edge of CLK is ignored and the internal
falling edge is generated by a phase-locked loop. The
input clock duty cycle can vary from 40% to 60% and the
clock duty cycle stabilizer will maintain a constant 50%
internal duty cycle. If the clock is turned off for a long
period of time, the duty cycle stabilizer circuit will require
a hundred clock cycles for the PLL to lock onto the input
clock. To use the clock duty cycle stabilizer, the MODE pin
should be connected to 1/3V
DD
or 2/3V
DD
using external
resistors. The MODE pin controls both Channel A and
Channel B--the duty cycle stabilizer is either on or off for
both channels.
The lower limit of the LTC2288/LTC2287/LTC2286 sample
rate is determined by droop of the sample-and-hold cir-
cuits. The pipelined architecture of this ADC relies on
storing analog signals on small valued capacitors. Junc-
tion leakage will discharge the capacitors. The specified
minimum operating frequency for the LTC2288/LTC2287/
LTC2286 is 1Msps.
DIGITAL OUTPUTS
Digital Output Buffers
Figure 12 shows an equivalent circuit for a single output
buffer. Each buffer is powered by OV
DD
and OGND, iso-
lated from the ADC power and ground. The additional
N-channel transistor in the output driver allows operation
down to low voltages. The internal resistor in series with
the output makes the output appear as 50 to external
circuitry and may eliminate the need for external damping
resistors.
As with all high speed/high resolution converters, the digi-
tal output loading can affect the performance. The digital
outputs of the LTC2288/LTC2287/LTC2286 should drive a
minimal capacitive load to avoid possible interaction
Figure 11. Sinusoidal Single-Ended CLK Drive
CLK
50
0.1F
0.1F
4.7F
1k
1k
FERRITE
BEAD
CLEAN
SUPPLY
SINUSOIDAL
CLOCK
INPUT
228876 F11
NC7SVU04
LTC2288
LTC2287
LTC2286
LTC2288/LTC2287/LTC2286
21
228876f
between the digital outputs and sensitive input circuitry.
The output should be buffered with a device such as an
ALVCH16373 CMOS latch. For full speed operation the
capacitive load should be kept under 10pF.
Lower OV
DD
voltages will also help reduce interference
from the digital outputs.
Data Format
Using the MODE pin, the LTC2288/LTC2287/LTC2286
parallel digital output can be selected for offset binary or
2's complement format. Note that MODE controls both
Channel A and Channel B. Connecting MODE to GND or
1/3V
DD
selects straight binary output format. Connecting
MODE to 2/3V
DD
or V
DD
selects 2's complement output
format. An external resistor divider can be used to set the
1/3V
DD
or 2/3V
DD
logic values. Table 1 shows the logic
states for the MODE pin.
APPLICATIO S I FOR ATIO
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Overflow Bit
When OF outputs a logic high the converter is either
overranged or underranged.
Output Driver Power
Separate output power and ground pins allow the output
drivers to be isolated from the analog circuitry. The power
supply for the digital output buffers, OV
DD
, should be tied
to the same power supply as for the logic being driven. For
example, if the converter is driving a DSP powered by a 1.8V
supply, then OV
DD
should be tied to that same 1.8V supply.
OV
DD
can be powered with any voltage from 500mV up to
3.6V. OGND can be powered with any voltage from GND up
to 1V and must be less than OV
DD
. The logic outputs will
swing between OGND and OV
DD
.
Output Enable
The outputs may be disabled with the output enable pin, OE.
OE high disables all data outputs including OF. The data ac-
cess and bus relinquish times are too slow to allow the
outputs to be enabled and disabled during full speed op-
eration. The output Hi-Z state is intended for use during long
periods of inactivity. Channels A and B have independent
output enable pins (OEA, OEB).
Table 1. MODE Pin Function
Clock Duty
MODE Pin
Output Format
Cycle Stabilizer
0
Straight Binary
Off
1/3V
DD
Straight Binary
On
2/3V
DD
2's Complement
On
V
DD
2's Complement
Off
Figure 12. Digital Output Buffer
228876 F12
OV
DD
V
DD
V
DD
0.1F
43
TYPICAL
DATA
OUTPUT
OGND
OV
DD
0.5V
TO V
DD
PREDRIVER
LOGIC
DATA
FROM
LATCH
OE
LTC2288/LTC2287/LTC2286
LTC2288/LTC2287/LTC2286
22
228876f
APPLICATIO S I FOR ATIO
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Sleep and Nap Modes
The converter may be placed in shutdown or nap modes
to conserve power. Connecting SHDN to GND results in
normal operation. Connecting SHDN to V
DD
and OE to V
DD
results in sleep mode, which powers down all circuitry
including the reference and typically dissipates 1mW. When
exiting sleep mode it will take milliseconds for the output
data to become valid because the reference capacitors have
to recharge and stabilize. Connecting SHDN to V
DD
and OE
to GND results in nap mode, which typically dissipates
30mW. In nap mode, the on-chip reference circuit is kept
on, so that recovery from nap mode is faster than that from
sleep mode, typically taking 100 clock cycles. In both sleep
and nap modes, all digital outputs are disabled and enter
the Hi-Z state.
Channels A and B have independent SHDN pins (SHDNA,
SHDNB). Channel A is controlled by SHDNA and OEA, and
Channel B is controlled by SHDNB and OEB. The nap, sleep
and output enable modes of the two channels are completely
independent, so it is possible to have one channel operat-
ing while the other channel is in nap or sleep mode.
Digital Output Mulitplexer
The digital outputs of the LTC2288/LTC2287/LTC2286 can
be multiplexed onto a single data bus. The MUX pin is a
digital input that swaps the two data busses. If MUX is High,
Channel A comes out on DA0-DA9, OFA; Channel B comes
out on DB0-DB9, OFB. If MUX is Low, the output busses
are swapped and Channel A comes out on DB0-DB9, OFB;
Channel B comes out on DA0-DA9, OFA. To multiplex both
channels onto a single output bus, connect MUX, CLKA and
CLKB together (see the Timing Diagram for the multiplexed
mode). The multiplexed data is available on either data
bus--the unused data bus can be disabled with its OE pin.
Grounding and Bypassing
The LTC2288/LTC2287/LTC2286 requires a printed cir-
cuit board with a clean, unbroken ground plane. A multi-
layer board with an internal ground plane is recom-
mended. Layout for the printed circuit board should en-
sure that digital and analog signal lines are separated as
much as possible. In particular, care should be taken not
to run any digital track alongside an analog signal track or
underneath the ADC.
High quality ceramic bypass capacitors should be used at
the V
DD
, OV
DD
, V
CM
, REFH, and REFL pins. Bypass capaci-
tors must be located as close to the pins as possible. Of
particular importance is the 0.1F capacitor between
REFH and REFL. This capacitor should be placed as close
to the device as possible (1.5mm or less). A size 0402
ceramic capacitor is recommended. The large 2.2F ca-
pacitor between REFH and REFL can be somewhat further
away. The traces connecting the pins and bypass capaci-
tors must be kept short and should be made as wide as
possible.
The LTC2288/LTC2287/LTC2286 differential inputs should
run parallel and close to each other. The input traces
should be as short as possible to minimize capacitance
and to minimize noise pickup.
Heat Transfer
Most of the heat generated by the LTC2288/LTC2287/
LTC2286 is transferred from the die through the bottom-
side exposed pad and package leads onto the printed
circuit board. For good electrical and thermal perfor-
mance, the exposed pad should be soldered to a large
grounded pad on the PC board. It is critical that all ground
pins are connected to a ground plane of sufficient area.
LTC2288/LTC2287/LTC2286
23
228876f
C21
0.1
F
C27
0.1
F
V
DD
V
DD
V
DD
V
DD
V
DD
V
CC
V
CMB
C20
2.2
F
C18 1
F
C23 1
F
C34
0.1
F
C31
12pF
C17
0.1
F
C14
0.1
F
C25
0.1
F
C30
18pF
L2
47nH
R28
24
C32
18pF
C28
2.2
F
C35
0.1
F
C24
0.1
F
C36
4.7
F
E3
V
DD
3V
E5
PWR
GND
V
DD
V
CC
V
CC
228876 AI01
C1
0.1
F
R16
33
R1
1k
R2
1k
R3
1k
R10
1k
R14
49.9
R20
24.9
R18
24.9
R24
24.9
R17
OPT
R22
24.9
R23
51
T2
ETC1-1T
C29
0.1
F
C33
0.1
F
J3
CLOCK
INPUT
U6
NC7SVU04
U4
NC7SV86P5X
U7
NC7SV86P5X
U3
NC7SVU04
C13
0.1
F
C15
0.1
F
C12
4.7
F
6.3V
L1
BEAD
V
DD
C19
0.1
F
C11
0.1
F
C4
0.1
F
C2
2.2
F
C10
2.2
F
C9 1
F
C13 1
F
R15
1k
J4
ANALOG
INPUT B
V
CC
1
2
3
4
5
V
CMB
C8
0.1
F
C6
12pF
C44
0.1
F
R6
24.9
R5
24.9
R9
24.9
R4
OPT
R7
24.9
R8
51
T1
ETC1-1T
C3
0.1
F
C7
0.1
F
J2
ANALOG
INPUT A
1
2
3
5
4
V
CMA
V
CMA
12
V
DD
V
DD
34
2/3V
DD
56
1/3V
DD
78
GND
JP1 MODE
C16 0.1
F
25
23
27
29
31
33
35
37
39
21
19
15
17
13
9
7
1
3
5
2
4
11
26
24
30
28
34
32
38
40
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
40
3201S-40G1
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
36
22
20
16
18
14
10
8
6
12
R13
10k
R11
10k
R12
10k
R30
15
R
N1D
33
R
N1C
33
R
N1B
33
R
N1A
33
R
N2D
33
R
N2C
33
R
N2B
33
R
N2A
33
R
N3D
33
R
N3C
33
R
N3B
33
R
N3A
33
R
N4D
33
R
N4C
33
R
N4B
33
C39
1
F
C38
0.01
F
V
CC
V
DD
BYP
GND
ADJ
OUT
SHDN
GND
IN
1
2
3
4
8
U8
LT1763
7
6
5
GND
R26
100k
R25
105k
C37
10
F
6.3V
E4
GND
C40
0.1
F
C41
0.1
F
A
INA
+
A
INA
REFHA
REFHA
REFLA
REFLA
V
DD
CLKA
CLKB
V
DD
REFLB
REFLB
REFHB
REFHB
A
INB
A
INB
+
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
DA3
DA2
DA1
DA0
NC
NC
NC
NC
OFB
DB9
DB8
DB7
DB6
DB5
DB4
DB3
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
GND
V
DD
SENSEA
VCMA
MODE
SHDNA
OEA
OFA
DA9
DA8
DA7
DA6
DA5
DA4
OGND
OV
DD
GND
V
DD
SENSEB
VCMB
MUX
SHDNB
OEB
NC
NC
NC
NC
DB0
DB1
DB2
OGND
OV
DD
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
E2
EXT
REF B
12
V
DD
34
V
CM
V
DD
V
CMB
56
EXT REF
JP3 SENSE
E1
EXT
REF A
12
V
DD
34
V
CM
V
DD
56
EXT REF
JP2 SENSE A
C5
0.1
F
C26
0.1
F
V
CC
B3
B2
B4
B5
B6
B7
OE
B1
B0
A3
A1
A0
18
17
16
15
14
13
12
11
19
2
20
V
CC
74VCX245BQX
V
CC
3
4
5
6
7
8
9
1
10
A2
A7
T/R
GND
A5
A4
A6
B3
B2
B4
B5
B6
B7
OE
B1
B0
A3
A1
A0
18
17
16
15
14
13
12
11
19
2
20
V
CC
74VCX245BQX
V
CC
3
4
5
6
7
8
9
1
10
A2
A7
T/R
GND
A5
A4
A6
A0
A1
A2
A3
V
CC
WP
SCL
SDA
1
2
3
4
8
7
6
5
R29
51
L4
47nH
C43
8.2pF
L3
47nH
C42
8.2pF
U5
24LC025
V
CC
R31
TBD
R27
TBD
V
CC
U10
NC7SV86P5X
R32
22
U1
LTC2288
APPLICATIO S I FOR ATIO
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LTC2288/LTC2287/LTC2286
24
228876f
APPLICATIO S I FOR ATIO
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Silkscreen Top
Top Side
LTC2288/LTC2287/LTC2286
25
228876f
APPLICATIO S I FOR ATIO
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Inner Layer 2 GND
Inner Layer 3 Power
LTC2288/LTC2287/LTC2286
26
228876f
APPLICATIO S I FOR ATIO
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Bottom Side
LTC2288/LTC2287/LTC2286
27
228876f
PACKAGE DESCRIPTIO
U
UP Package
64-Lead Plastic QFN (9mm 9mm)
(Reference LTC DWG # 05-08-1705)
9 .00 0.10
(4 SIDES)
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION WNJR-5
2. ALL DIMENSIONS ARE IN MILLIMETERS
3. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT
4. EXPOSED PAD SHALL BE SOLDER PLATED
5. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
6. DRAWING NOT TO SCALE
PIN 1 TOP MARK
(SEE NOTE 5)
0.40 0.10
64
63
1
2
BOTTOM VIEW--EXPOSED PAD
7.15 0.10
(4-SIDES)
0.75 0.05
R = 0.115
TYP
0.25 0.05
0.50 BSC
0.200 REF
0.00 0.05
(UP64) QFN 1003
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.70 0.05
7.15 0.05
(4 SIDES)
8.10 0.05 9.50 0.05
0.25 0.05
0.50 BSC
PACKAGE OUTLINE
PIN 1
CHAMFER
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC2288/LTC2287/LTC2286
28
228876f
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
FAX: (408) 434-0507
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2005
LT/TP 0105 1K PRINTED IN USA
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1403A/LTC1403
14-Bit/12-Bit 2.8Msps Serial ADC
3V, 14mW, Differential Input, MSOP Package
LTC1407A/LTC1407
14-Bit/12-Bit 3Msps, Simultaneous Sampling Serial ADC
3V, 14mW, 2-Ch. Differential Input, MSOP Package
LTC1749
12-Bit, 80Msps Wideband ADC
Up to 500MHz IF Undersampling, 87dB SFDR
LTC1750
14-Bit, 80Msps Wideband ADC
Up to 500MHz IF Undersampling, 90dB SFDR
LTC2225
12-Bit, 10Msps ADC
60mW, 71dB SNR, 5mm 5mm QFN
LTC2226
12-Bit, 25Msps ADC
75mW, 71dB SNR, 5mm 5mm QFN
LTC2227
12-Bit, 40Msps ADC
125mW, 71dB SNR, 5mm 5mm QFN
LTC2228
12-Bit, 65Msps ADC
210mW, 71dB SNR, 5mm 5mm QFN
LTC2229
12-Bit, 80Msps ADC
230mW, 70.6dB SNR, 5mm 5mm QFN
LTC2236
10-Bit, 25Msps ADC
75mW, 61dB SNR, 5mm 5mm QFN
LTC2237
10-Bit, 40Msps ADC
125mW, 61dB SNR, 5mm 5mm QFN
LTC2238
10-Bit, 65Msps ADC
210mW, 61dB SNR, 5mm 5mm QFN
LTC2239
10-Bit, 80Msps ADC
230mW, 61dB SNR, 5mm 5mm QFN
LTC2245
14-Bit, 10Msps ADC
60mW, 74.4dB SNR, 5mm 5mm QFN
LTC2246
14-Bit, 25Msps ADC
75mW, 74dB SNR, 5mm 5mm QFN
LTC2247
14-Bit, 40Msps ADC
125mW, 74dB SNR, 5mm 5mm QFN
LTC2248
14-Bit, 65Msps ADC
210mW, 74dB SNR, 5mm 5mm QFN
LTC2249
14-Bit, 80Msps ADC
230mW, 73dB SNR, 5mm 5mm QFN
LTC2289
Dual 10-Bit, 80Msps ADC
445mW, 61dB SNR, 9mm 9mm QFN
LTC2290
Dual 12-Bit, 10Msps ADC
120mW, 71dB SNR, 9mm 9mm QFN
LTC2291
Dual 12-Bit, 25Msps ADC
150mW, 71dB SNR, 9mm 9mm QFN
LTC2292
Dual 12-Bit, 40Msps ADC
235mW, 71dB SNR, 9mm 9mm QFN
LTC2293
Dual 12-Bit, 65Msps ADC
400mW, 71dB SNR, 9mm 9mm QFN
LTC2294
Dual 12-Bit, 80Msps ADC
445mW, 70.6dB SNR, 9mm 9mm QFN
LTC2295
Dual 14-Bit, 10Msps ADC
120mW, 74.4dB SNR, 9mm 9mm QFN
LTC2296
Dual 14-Bit, 25Msps ADC
150mW, 74dB SNR, 9mm 9mm QFN
LTC2297
Dual 14-Bit, 40Msps ADC
235mW, 74dB SNR, 9mm 9mm QFN
LTC2298
Dual 14-Bit, 65Msps ADC
400mW, 74dB SNR, 9mm 9mm QFN
LTC2299
Dual 14-Bit, 80Msps ADC
445mW, 73dB SNR, 9mm 9mm QFN
LT5512
DC-3GHz High Signal Level Downconverting Mixer
DC to 3GHz, 21dBm IIP3, Integrated LO Buffer
LT5514
Ultralow Distortion IF Amplifier/ADC Driver
450MHz 1dB BW, 47dB OIP3, Digital Gain
with Digitally Controlled Gain
Control 10.5dB to 33dB in 1.5dB/Step
LT5515
1.5GHz to 2.5GHz Direct Conversion Quadrature Demodulator
20dBm IIP3, Integrated LO Quadrature Generator
LT5516
0.8GHz to 1.5GHz Direct Conversion Quadrature Demodulator
21.5dBm IIP3, Integrated LO Quadrature Generator
LT5517
40MHz to 900MHz Direct Conversion Quadrature Demodulator
21dBm IIP3, Integrated LO Quadrature Generator
LT5522
600MHz to 2.7GHz High Linearity Downconverting Mixer
4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB,
50 Single Ended RF and LO Ports
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