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LTC2435/LTC2435-1
1
24351fa
2
Speed Up Version of the LTC2430: 15Hz Output
Rate, 60Hz Notch--LTC2435; 13.75Hz Output Rate,
Simultaneous 50Hz/60Hz Notch--LTC2435-1
Differential Input and Differential Reference with
GND to V
CC
Common Mode Range
3ppm INL, No Missing Codes
10ppm Gain Error
0.8ppm Noise
Single Conversion Settling Time for Multiplexed
Applications
Internal Oscillator--No External Components
Required
Single Supply 2.7V to 5.5V Operation
Low Supply Current (200A,4A in Auto Sleep)
20-Bit ADC in Narrow SSOP-16 Package
(SO-8 Footprint)
The LTC
2435/2435-1 are 2.7V to 5.5V micropower
20-bit differential analog to digital converters with
integrated oscillator, 3ppm INL and 0.8ppm RMS noise.
They use delta-sigma technology and provide single cycle
settling time for multiplexed applications. Through a
single pin, the LTC2435 can be configured for better than
110dB input differential mode rejection at 50Hz or 60Hz
2%, or it can be driven by an external oscillator for a user
defined rejection frequency. The LTC2435-1 can be con-
figured for better than 87dB input differential mode rejec-
tion over the range of 49Hz to 61.2Hz (50Hz and 60Hz
2% simultaneously). The internal oscillator requires no
external frequency setting components.
The converters accept any external differential reference
voltage from 0.1V to V
CC
for flexible ratiometric and
remote sensing measurement configurations. The full-
scale differential input range is from 0.5V
REF
to 0.5V
REF
.
The reference common mode voltage, V
REFCM
, and the
input common mode voltage, V
INCM
, may be indepen-
dently set anywhere within the GND to V
CC
range of the
LTC2435/LTC2435-1. The DC common mode input rejec-
tion is better than 120dB.
The LTC2435/LTC2435-1 communicate through a flexible
3-wire digital interface which is compatible with SPI and
MICROWIRE
TM
protocols.
, LTC and LT are registered trademarks of Linear Technology Corporation.
20-Bit No Latency
TM
ADCs with Differential Input and
Differential Reference
No Latency is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
Protected by U.S. Patents including 6140950, 6169506.
V
CC
F
O
REF
+
REF
SCK
IN
+
IN
SDO
GND
CS
2
14
3
4
13
5
6
12
1, 7, 8, 9, 10, 15, 16
11
REFERENCE
VOLTAGE
0.1V TO V
CC
ANALOG INPUT RANGE
0.5V
REF
TO 0.5V
REF
= INTERNAL OSC/50Hz REJECTION (LTC2435)
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION (LTC2435)
= INTERNAL 50Hz/60Hz REJECTION (LTC2435-1)
3-WIRE
SPI INTERFACE
1F
2.7V TO 5.5V
LTC2435/
LTC2435-1
2435 TA01
V
CC
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO S
U
APPLICATIO S
U
Direct Sensor Digitizer
Weight Scales
Direct Temperature Measurement
Gas Analyzers
Strain Gage Transducers
Instrumentation
Data Acquisition
Industrial Process Control
6-Digit DVMs
10
8
6
4
2
0
2
4
6
8
10
INPUT VOLTAGE (V)
2.5
1.5
0.5
0.5
1.5
2435 G04
2.5
F
O
= GND
V
CC
= 5V
V
REF
= 5V
V
INCM
= V
INCM
= 2.5V
T
A
= 45C
T
A
= 25C
T
A
= 85C
INL (ppm OF V
REF
)
Integral Nonlinearity vs Input
LTC2435/LTC2435-1
2
24351fa
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
ELECTRICAL CHARACTERISTICS
(Notes 1, 2)
ORDER PART NUMBER
Supply Voltage (V
CC
) to GND ....................... 0.3V to 7V
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
LTC2435C/LTC2435-1C ........................... 0C to 70C
LTC2435I/LTC2435-1I ........................ 40C to 85C
Storage Temperature Range ................. 65C to 150C
Lead Temperature (Soldering, 10 sec).................. 300C
T
JMAX
= 125C,
JA
= 95C/W
LTC2435CGN
LTC2435IGN
LTC2435-1CGN
LTC2435-1IGN
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)
20
Bits
Integral Nonlinearity
5V V
CC
5.5V, REF
+
= 2.5V, REF
= GND, V
INCM
= 1.25V, (Note 6)
2
ppm of V
REF
5V V
CC
5.5V, REF
+
= 5V, REF
= GND, V
INCM
= 2.5V, (Note 6)
3
20
ppm of V
REF
2.7V V
CC
5.5V, REF
+
= 2.5V, REF
= GND, V
INCM
= 1.25V, (Note 6)
10
ppm of V
REF
Offset Error
2.5V REF
+
V
CC
, REF
= GND,
2
5
mV
GND IN
+
= IN
V
CC
, (Note 14)
Offset Error Drift
2.5V REF
+
V
CC
, REF
= GND,
100
nV/C
GND IN
+
= IN
V
CC
Positive Gain Error
2.5V REF
+
V
CC
, REF
= GND,
10
25
ppm of V
REF
IN
+
= 0.75REF
+
, IN
= 0.25 REF
+
Positive Gain Error Drift
2.5V REF
+
V
CC
, REF
= GND,
0.1
ppm of V
REF
/C
IN
+
= 0.75REF
+
, IN
= 0.25 REF
+
Negative Gain Error
2.5V REF
+
V
CC
, REF
= GND,
10
25
ppm of V
REF
IN
+
= 0.25 REF
+
, IN
= 0.75 REF
+
Negative Gain Error Drift
2.5V REF
+
V
CC
, REF
= GND,
0.1
ppm of V
REF
/C
IN
+
= 0.25 REF
+
, IN
= 0.75 REF
+
Output Noise
5V V
CC
5.5V, REF
+
= 5V, REF
= GND,
4
V
RMS
GND IN
= IN
+
V
CC
, (Note 13)
The
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. (Notes 3, 4)
GN PART MARKING
2435
2435I
24351
24351I
TOP VIEW
GN PACKAGE
16-LEAD PLASTIC SSOP
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND
V
CC
REF
+
REF
IN
+
IN
GND
GND
GND
GND
F
O
SCK
SDO
CS
GND
GND
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. (Notes 3, 4)
CO VERTER CHARACTERISTICS
U
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Common Mode Rejection DC
2.5V REF
+
V
CC
, REF
= GND,
110
120
dB
GND IN
= IN
+
V
CC
(Note 5)
LTC2435/LTC2435-1
3
24351fa
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
IN
+
Absolute/Common Mode IN
+
Voltage
GND 0.3V
V
CC
+ 0.3V
V
IN
Absolute/Common Mode IN
Voltage
GND 0.3V
V
CC
+ 0.3V
V
V
IN
Input Differential Voltage Range
V
REF
/2
V
REF
/2
V
(IN
+
IN
)
REF
+
Absolute/Common Mode REF
+
Voltage
0.1
V
CC
V
REF
Absolute/Common Mode REF
Voltage
GND
V
CC
0.1V
V
V
REF
Reference Differential Voltage Range
0.1
V
CC
V
(REF
+
REF
)
C
S
(IN
+
)
IN
+
Sampling Capacitance
1.5
pF
C
S
(IN
)
IN
Sampling Capacitance
1.5
pF
C
S
(REF
+
)
REF
+
Sampling Capacitance
1.5
pF
C
S
(REF
)
REF
Sampling Capacitance
1.5
pF
I
DC_LEAK
(IN
+
)
IN
+
DC Leakage Current
CS = V
CC
, IN
+
= GND
10
1
10
nA
I
DC_LEAK
(IN
)
IN
DC Leakage Current
CS = V
CC
, IN
= V
CC
10
1
10
nA
I
DC_LEAK
(REF
+
)
REF
+
DC Leakage Current
CS = V
CC
, REF
+
= V
CC
10
1
10
nA
I
DC_LEAK
(REF
)
REF
DC Leakage Current
CS = V
CC
, REF
= GND
10
1
10
nA
The
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. (Note 3)
The
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. (Notes 3, 4)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
CO VERTER CHARACTERISTICS
U
A ALOG I PUT A
U
D REFERE CE
U
U
U
Input Common Mode Rejection
2.5V REF
+
V
CC
, REF
= GND,
140
dB
60Hz 2% (LTC2435)
GND IN
= IN
+
V
CC
, (Notes 5, 7)
Input Common Mode Rejection
2.5V REF
+
V
CC
, REF
= GND,
140
dB
50Hz 2% (LTC2435)
GND IN
= IN
+
V
CC
, (Notes 5, 8)
Input Normal Mode Rejection
(Notes 5, 7)
110
120
dB
60Hz 2% (LTC2435)
Input Normal Mode Rejection
(Notes 5, 8)
110
120
dB
50Hz 2% (LTC2435)
Input Common Mode Rejection
2.5V REF
+
V
CC
, REF
= GND,
120
dB
49Hz to 61.2Hz (LTC2435-1)
GND IN
= IN
+
V
CC
, (Notes 5, 7)
Input Normal Mode Rejection
F
O
= GND (Note 5)
87
dB
49Hz to 61.2Hz (LTC2435-1)
Input Normal Mode Rejection
External Oscillator (Note 5)
87
dB
External Clock f
EOSC
/2560 14%
Input Normal Mode Rejection
External Oscillator (Note 5)
110
120
dB
External Clock f
EOSC
/2560 4%
Reference Common Mode
2.5V REF
+
V
CC
, GND REF
2.5V,
130
140
dB
Rejection DC
V
REF
= 2.5V, IN
= IN
+
= GND (Note 5)
Power Supply Rejection, DC
REF
+
= V
CC
, REF
= GND, IN
= IN
+
= GND
100
dB
Power Supply Rejection, 60Hz 2% REF
+
= 2.5V, REF
= GND, IN
= IN
+
= GND, (Note 7)
120
dB
Power Supply Rejection, 50Hz 2% REF
+
= 2.5V, REF
= GND, IN
= IN
+
= GND, (Note 8)
120
dB
LTC2435/LTC2435-1
4
24351fa
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Supply Voltage
2.7
5.5
V
I
CC
Supply Current
Conversion Mode
CS = 0V (Note 12)
200
300
A
Sleep Mode
CS = V
CC
(Note 12)
4
10
A
Sleep Mode
CS = V
CC
, 2.7V V
CC
3.3V (Note 12)
2
A
The
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25C. (Note 3)
The
denotes specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25C. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IH
High Level Input Voltage
2.7V V
CC
5.5V
2.5
V
CS, F
O
2.7V V
CC
3.3V
2.0
V
V
IL
Low Level Input Voltage
4.5V V
CC
5.5V
0.8
V
CS, F
O
2.7V V
CC
5.5V
0.6
V
V
IH
High Level Input Voltage
2.7V V
CC
5.5V (Note 9)
2.5
V
SCK
2.7V V
CC
3.3V (Note 9)
2.0
V
V
IL
Low Level Input Voltage
4.5V V
CC
5.5V (Note 9)
0.8
V
SCK
2.7V V
CC
5.5V (Note 9)
0.6
V
I
IN
Digital Input Current
0V V
IN
V
CC
10
10
A
CS, F
O
I
IN
Digital Input Current
0V V
IN
V
CC
(Note 9)
10
10
A
SCK
C
IN
Digital Input Capacitance
10
pF
CS, F
O
C
IN
Digital Input Capacitance
(Note 9)
10
pF
SCK
V
OH
High Level Output Voltage
I
O
= 800A
V
CC
0.5
V
SDO
V
OL
Low Level Output Voltage
I
O
= 1.6mA
0.4
V
SDO
V
OH
High Level Output Voltage
I
O
= 800A (Note 10)
V
CC
0.5
V
SCK
V
OL
Low Level Output Voltage
I
O
= 1.6mA (Note 10)
0.4
V
SCK
I
OZ
Hi-Z Output Leakage
10
10
A
SDO
DIGITAL I PUTS A D DIGITAL OUTPUTS
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POWER REQUIRE E TS
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LTC2435/LTC2435-1
5
24351fa
Note 1: Absolute Maximum Ratings are those values beyond which the
life of the device may be impaired.
Note 2: All voltage values are with respect to GND.
Note 3: V
CC
= 2.7 to 5.5V unless otherwise specified.
V
REF
= REF
+
REF
, V
REFCM
= (REF
+
+ REF
)/2;
V
IN
= IN
+
IN
, V
INCM
= (IN
+
+ IN
)/2.
Note 4: F
O
pin tied to GND or to V
CC
or to external conversion clock
source with f
EOSC
= 153600Hz unless otherwise specified.
Note 5: Guaranteed by design, not subject to test.
Note 6: 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 7: F
O
= 0V (internal oscillator) or f
EOSC
= 153600Hz 2%
(external oscillator) for the LTC2435 or f
EOSC
= 139800Hz 2% for the
LTC2435-1.
Note 8: F
O
= V
CC
(internal oscillator) or f
EOSC
= 128000Hz 2%
(external oscillator).
Note 9: The converter is in external SCK mode of operation such that
the SCK pin is used as digital input. The frequency of the clock signal
driving SCK during the data output is f
ESCK
and is expressed in kHz.
Note 10: The converter is in internal SCK mode of operation such that
the SCK pin is used as digital output. In this mode of operation the
SCK pin has a total equivalent load capacitance C
LOAD
= 20pF.
Note 11: The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in kHz.
Note 12: The converter uses the internal oscillator.
F
O
= 0V or F
O
= V
CC
.
Note 13: The output noise includes the contribution of the internal
calibration operations.
Note 14: Refer to Offset Accuracy and Drift in the Applications
Information section.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
f
EOSC
External Oscillator Frequency Range
5
2000
kHz
t
HEO
External Oscillator High Period
0.25
200
s
t
LEO
External Oscillator Low Period
0.25
200
s
t
CONV
Conversion Time (LTC2435)
F
O
= 0V
65.6
66.9
68.3
ms
F
O
= V
CC
78.7
80.3
81.9
ms
External Oscillator (Note 11)
10278/f
EOSC
(in kHz)
ms
Conversion Time (LTC2435-1)
F
O
= 0V
72
73.5
75
ms
External Oscillator (Note 11)
10278/f
EOSC
(in kHz)
ms
f
ISCK
Internal SCK Frequency
Internal Oscillator (Note 10), LTC2435
19.2
kHz
Internal Oscillator (Note 10), LTC2435-1
17.5
kHz
External Oscillator (Notes 10, 11)
f
EOSC
/8
kHz
D
ISCK
Internal SCK Duty Cycle
(Note 10)
45
55
%
f
ESCK
External SCK Frequency Range
(Note 9)
2000
kHz
t
LESCK
External SCK Low Period
(Note 9)
250
ns
t
HESCK
External SCK High Period
(Note 9)
250
ns
t
DOUT_ISCK
Internal SCK 24-Bit Data Output Time
Internal Oscillator (Notes 10, 12), LTC2435
1.22
1.25
1.28
ms
Internal Oscillator (Notes 10, 12), LTC2435-1
1.34
1.37
1.40
ms
External Oscillator (Notes 10, 11)
192/f
EOSC
(in kHz)
ms
t
DOUT_ESCK
External SCK 24-Bit Data Output Time (Note 9)
24/f
ESCK
(in kHz)
ms
t
1
CS to SDO Low Z
0
200
ns
t2
CS to SDO High Z
0
200
ns
t3
CS to SCK
(Note 10)
0
200
ns
t4
CS to SCK
(Note 9)
50
ns
t
KQMAX
SCK to SDO Valid
220
ns
t
KQMIN
SDO Hold After SCK
(Note 5)
15
ns
t
5
SCK Set-Up Before CS
50
ns
t
6
SCK Hold After CS
50
ns
The
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25C. (Note 3)
TI I G CHARACTERISTICS
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