2442f.indd
LTC2442
1
2442f
V
IN
DIFFERENTIAL (V)
2.048
5
ERROR (ppm)
4
2
1
0
5
2
1.024
0
2442 TA02
3
3
4
1
1.024
2.048
V
INCM
= 2.048V
V
REF
= 4.096V
V
CC
= 5V
V
+
= 5V
V
= 0V
24-Bit High Speed
4-Channel ADC
with Integrated Amplifi er
The LTC
2442 is an ultra high precision, variable speed,
24-bit
TM
ADC with integrated amplifi er. The amplifi er
can be confi gured as a buffer for easy input drive of high
impedance sensors. 1 part-per-million (ppm) linearity is
achievable when the amplifi er is confi gured in unity gain.
External resistors can be used to set a gain for increased
resolution of low level input signals. The positive and
negative amplifi er supply pins may be tied directly to V
CC
(4.5V to 5.5V) and GND or biased above V
CC
and below
GND for rail-to-rail input signals.
The proprietary architecture ensures stable DC ac-
curacy through continuous transparent calibration. Ten
speed/resolution combinations from 6.9Hz/220nV
RMS
to
3.5kHz/25V
RMS
can be selected with no latency or shift
in DC accuracy. Additionally, a 2X speed mode can be
selected enabling output rates up to 7kHz (8kHz with an
external oscillator) with one cycle latency.
Any combination of single-ended (up to 4 inputs) or dif-
ferential (up to 2 inputs) can be selected with a common
mode input range from ground to V
CC
. While operating in
the 1X speed mode the fi rst conversion following a new
speed/resolution or channel selection is valid.
Auto Ranging 6-Digit DVMs
High Speed Multiplexing
Weight Scales
Direct Temperature Measurement
High Speed Data Acquisition
1ppm Linearity with No Missing Codes
Integrated Amplifi er for Direct Sensor Digitization
2 Differential or 4 Single-Ended Input Channels
Up to 8kHz Output Rate
Up to 4kHz Multiplexing Rate
Selectable Speed/Resolution
2V
RMS
Noise at 1.76kHz Output Rate
220nV
RMS
Noise at 13.8Hz Output Rate with
Simultaneous 50Hz/60Hz Rejection
Guaranteed Modulator Stability and Lock-Up
Immunity for any Input and Reference Conditions
<5V Offset (4.5V < V
CC
< 5.5V, 40C to 85C)
Differential Input and Differential Reference with GND
to V
CC
Common Mode Range
No Latency Mode, Each Conversion is Accurate Even
After a New Channel is Selected
Internal Oscillator--No External Components
36-Lead SSOP Package
High Precision Data Acquisition System
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency
is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6140950, 6169506, 6411242, 6639526.
LTC2442 Integral Non-Linearity
SDI
SCK
SDO
CS
F
O
V
CC
4.5V TO 5.5V
4.5V TO 15V
15V TO 0V
0.1
F
GND
V
REF
V
REF
+
2442 TA01
4-WIRE
SPI INTERFACE
LTC2442
= EXTERNAL OSCILLATOR
= INTERNAL OSCILLATOR
(SIMULTANEOUS 50Hz/60Hz
REJECTION AT 6.9Hz OUTPUT RATE)
CH0
CH1
CH2
CH3
COM
0.1
F
AUTO-CAL
VARIABLE SPEED/
RESOLUTION
DIFFERENTIAL
24-BIT
ADC
HIGH Z
2-CHANNEL
DIFFERENTIAL/
4-CHANNEL
SINGLE ENDED
+
+
V
+
V
LTC2442
2
2442f
Supply Voltage (V
CC
) to GND ....................... 0.3V to 6V
Analog Input Pins Voltage
to GND ...................................... 0.3V to (V
CC
+ 0.3V)
Reference Input Pins Voltage
to GND ...................................... 0.3V to (V
CC
+ 0.3V)
Digital Input Voltage to GND ......... 0.3V to (V
CC
+ 0.3V)
Digital Output Voltage to GND ....... 0.3V to (V
CC
+ 0.3V)
Operating Temperature Range
LTC2442CG .................................................. 0C to 70C
LTC2442IG ............................................... 40C to 85C
Storage Temperature Range ................... 65C to 150C
Lead Temperature (Soldering, 10 sec) .................. 300C
Amplifi er Supply Voltage (V
+
to V
) ..........................36V
(Notes 1, 2)
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25C. (Notes 3, 4, 15)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Resolution (No Missing Codes)
0.1V V
REF
V
CC
, 0.5 V
REF
V
IN
0.5 V
REF
(Note 5)
24
Bits
Integral Nonlinearity
V
CC
= 5V, REF
+
= 5V, REF
= GND, V
INCM
= 2.5V (Note 6, 14)
V
CC
= 5V, REF
+
= 2.5V, REF
= GND, V
INCM
= 1.25V (Note 6, 14)
REF
+
= 4.096V, REF
= GND, V
INCM
= 2.048V (Note 6, 14)
2
2
1
10
7
ppm of V
REF
ppm of V
REF
ppm of V
REF
Offset Error
2.5V REF
+
V
CC
, REF
= GND,
GND SEL
+
= SEL
V
CC
(Note 12)
2.5
5
V
Offset Error Drift
2.5V REF
+
V
CC
, REF
= GND,
GND SEL
+
= SEL
V
CC
20
nV/C
Positive Full-Scale Error
REF
+
= 5V, REF
= GND, SEL
+
= 3.75V, SEL
= 1.25V
REF
+
= 2.5V, REF
= GND, SEL
+
= 1.875V, SEL
= 0.625V
10
10
50
50
ppm of V
REF
ppm of V
REF
Positive Full-Scale Error Drift
2.5V REF
+
V
CC
, REF
= GND,
SEL
+
= 0.75 REF
+
, SEL
= 0.25 REF
+
0.2
ppm of V
REF
/C
ELECTRICAL CHARACTERISTICS
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TOP VIEW
G PACKAGE
36-LEAD PLASTIC SSOP
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
SCK
BUSY
EXT
DGND
AGND
CH0
CH1
CH2
CH3
ADCINB
ADCINA
OUTA
INA
NC
NC
NC
OUTB
INB
SDO
CS
F
O
SDI
GND
REF
REF
+
V
CC
COM
MUXOUTA
MUXOUTB
+INA
V
NC
NC
V+
NC
+INB
T
JMAX
= 125C,
JA
= 160C/W
ORDER PART NUMBER
PART MARKING
LTC2442CG
LTC2442IG
LTC2442CG
LTC2442IG
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
LTC2442
3
2442f
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SEL
+
Absolute/Common Mode SEL
+
Voltage
SEL
+
is the Positive Selected
Input Channel, see Table 3
GND 0.3
V
CC
+ 0.3
V
SEL
Absolute/Common Mode SEL
Voltage
SEL
is the Negative Selected
Input Channel, see Table 3
GND 0.3
V
CC
+ 0.3
V
V
IN
Input Differential Voltage Range
(SEL
+
SEL
)
V
REF
/2
V
REF
/2
V
REF
+
Absolute/Common Mode REF
+
Voltage
0.1
V
CC
V
REF
Absolute/Common Mode REF
Voltage
GND
V
CC
0.1
V
V
REF
Reference Differential Voltage Range
(REF
+
REF
)
0.1
V
CC
V
C
S(ADCINA)
ADCINA Sampling Capacitance
2
pF
C
S(ADCINB)
ADCINB Sampling Capacitance
2
pF
C
S(REF
+
)
REF
+
Sampling Capacitance
2
pF
C
S(REF
)
REF
Sampling Capacitance
2
pF
I
DC_LEAK(SEL
+
, SEL
,
REF
+
, REF
)
Leakage Current, Inputs and Reference
CS = V
CC
, SEL
+
= GND, SEL
=
GND, REF
+
= 5V, REF
= GND
15
1
15
nA
t
OPEN
MUX Break-Before-Make
50
ns
QIRR
MUX Off Isolation
V
IN
= 2V
P-P
DC to 1.8MHz
120
dB
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25C. (Notes 3, 15)
A ALOG I PUT A
U
D REFERE CE
U
U
U
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25C. (Notes 3, 4, 15)
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Negative Full-Scale Error
REF
+
= 5V, REF
= GND, SEL
+
= 1.25V, SEL
= 3.75V
REF
+
= 2.5V, REF
= GND, SEL
+
= 0.625V, SEL
= 1.875V
10
10
50
50
ppm of V
REF
ppm of V
REF
Negative Full-Scale Error Drift
2.5V REF
+
V
CC
, REF
= GND,
SEL
+
= 0.25 REF
+
, SEL
= 0.75 REF
+
0.2
ppm of V
REF
/C
Total Unadjusted Error
5V V
CC
5.5V, REF
+
= 2.5V, REF
= GND, V
INCM
= 1.25V (Note 6)
5V V
CC
5.5V, REF
+
= 5V, REF
= GND, V
INCM
= 2.5V (Note 6)
REF
+
= 2.5V, REF
= GND, V
INCM
= 1.25V (Note 6)
12
12
12
ppm of V
REF
ppm of V
REF
ppm of V
REF
Input Common Mode Rejection DC
2.5V REF
+
V
CC
, REF
= GND,
GND SEL
= SEL
+
V
CC
120
dB
LTC2442
4
2442f
POWER REQUIRE E TS
W
U
The
denotes the specifi cations which apply over the full operating temperature
range, otherwise specifi cations are at T
A
= 25C. (Notes 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Supply Voltage
4.5
5.5
V
V
+
Amplifi er Positive Supply
4.5
15
V
V
Amplifi er Negative Supply
15
0
V
I
CC
Supply Current
Amplifi ers and ADC
10
13
mA
The
denotes the specifi cations which apply over the
full operating temperature range, otherwise specifi cations are at T
A
= 25C. (Note 3)
DIGITAL I PUTS A D DIGITAL OUTPUTS
U
U
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
CS, F
O
, EXT, SDI
4.5V V
CC
5.5V
2.5
V
V
IL
Low Level Input Voltage
CS, F
O
, EXT, SDI
4.5V V
CC
5.5V
0.8
V
V
IH
High Level Input Voltage
SCK
4.5V V
CC
5.5V (Note 8)
2.5
V
V
IL
Low Level Input Voltage
SCK
4.5V V
CC
5.5V (Note 8)
0.8
V
I
IN
Digital Input Current
CS, F
O
, EXT, SDI
0V V
IN
V
CC
10
10
A
I
IN
Digital Input Current
SCK
0V V
IN
V
CC
(Note 8)
10
10
A
C
IN
Digital Input Capacitance
CS, F
O
, EXT, SDI
10
pF
C
IN
Digital Input Capacitance
SCK
(Note 8)
10
pF
V
OH
High Level Output Voltage
SDO, BUSY
I
O
= 800A
V
CC
0.5
V
V
OL
Low Level Output Voltage
SDO, BUSY
I
O
= 1.6A
0.4
V
V
OH
High Level Output Voltage
SCK
I
O
= 800A (Note 9)
V
CC
0.5
V
V
OL
Low Level Output Voltage
SCK
I
O
= 1.6A (Note 9)
0.4
V
I
OZ
Hi-Z Output Leakage
SDO
10
10
A
LTC2442
5
2442f
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 GND.
Note 3: V
CC
= 4.5V to 5.5V unless otherwise specifi ed.
V
REF
= REF
+
REF
, V
REFCM
= (REF
+
+ REF
)/2;
V
IN
= SEL
+
SEL
, V
INCM
= (SEL
+
+ SEL
)/2.
Note 4: F
O
pin tied to GND or to external conversion clock source with
f
EOSC
= 10MHz unless otherwise specifi ed.
Note 5: Guaranteed by design, not subject to test.
Note 6: Integral nonlinearity is defi ned 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 7: The converter uses the internal oscillator.
Note 8: The converter is in external SCK mode of operation such that the
SCK pin is used as a digital input. The frequency of the clock signal driving
SCK during the data output is f
ESCK
and is expressed in Hz.
Note 9: The converter is in internal SCK mode of operation such that the
SCK pin is used as a digital output. In this mode of operation, the SCK pin
has a total equivalent load capacitance of C
LOAD
= 20pF.
Note 10: The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in Hz.
Note 11: The converter uses the internal oscillator. F
O
= 0V.
Note 12: Guaranteed by design and test correlation.
Note 13: There is an internal reset that adds an additional 1s (typ) to the
conversion time.
Note 14: In order to achieve optimum linearity, the amplifi er power
positive supply input (V
+
) must exceed the maximum input voltage level by
2V or greater. The negative amplifi er power supply input (V
) must be at
least 200mV below the minimum input voltage level.
Note 15: Amplifi ers are externally compensated with 0.1F.
TI I G CHARACTERISTICS
W
U
The
denotes the specifi cations which apply over the full operating temperature
range, otherwise specifi cations are at T
A
= 25C. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
EOSC
External Oscillator Frequency Range
0.1
20
MHz
t
HEO
External Oscillator High Period
25
10000
ns
t
LEO
External Oscillator Low Period
25
10000
ns
t
CONV
Conversion Time
OSR = 256 (SDI = 0)
OSR = 32768 (SDI = 1)
External Oscillator (Notes 10, 13)
0.99
126
1.13
145
40 OSR + 170
f
EOSC
(KHz)
1.33
170
ms
ms
ms
f
ISCK
Internal SCK Frequency
Internal Oscillator (Note 9)
External Oscillator (Notes 9, 10)
0.8
0.9
f
EOSC
/10
1
MHz
Hz
D
ISCK
Internal SCK Duty Cycle
(Note 9)
45
55
%
f
ESCK
External SCK Frequency Range
(Note 8)
20
MHz
fLESCK
External SCK Low Period
(Note 8)
25
ns
t
HESCK
External SCK High Period
(Note 8)
25
ns
t
DOUT_ISCK
Internal SCK 32-Bit Data Output Time
Internal Oscillator (Notes 9, 11)
External Oscillator (Notes 9, 10)
30.9
35.3
320/f
EOSC
41.6
s
s
t
DOUT_ESCK
External SCK 32-Bit Data Output Time
(Note 8)
32/f
ESCK
s
t
1
CS to SDO Low Z
(Note 12)
0
25
ns
t
2
CS to SDO High Z
(Note 12)
0
25
ns
t
3
CS to SCK
(Note 9)
5
s
t
4
CS to SCK
(Note 8, 12)
25
ns
t
KQMAX
SCK to SDO Valid
25
ns
t
KQMIN
SDO Hold After SCK
(Note 5)
15
ns
t
5
SCK Setup Before CS
50
ns
t
6
SCK Hold After CS
50
ns
t
7
SDI Setup Before SCK
(Note 5)
10
ns
t
8
SDI Hold After SCK
(Note 5)
10
ns
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