LTC2421/LTC2422
1-/2-Channel 20-Bit µPower
No Latency ∆ΣTMADCs in MSOP-10
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FEATURES
DESCRIPTIO
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20-Bit ADCs in Tiny MSOP-10 Packages
TheLTC®2421/LTC2422are1-and2-channel2.7Vto5.5V
micropower 20-bit analog-to-digital converters with an
integrated oscillator, 8ppm INL and 1.2ppm RMS noise.
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1- or 2-Channel Inputs
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Single Supply 2.7V to 5.5V Operation
Low Supply Current (200µA) and Auto Shutdown
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These ultrasmall devices use delta-sigma technology and
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Automatic Channel Selection (Ping-Pong) (LTC2422) anewdigitalfilterarchitecturethatsettlesinasinglecycle.
No Latency: Digital Filter Settles in a
Single Conversion Cycle
8ppm INL, No Missing Codes
4ppm Full-Scale Error
0.5ppm Offset
1.2ppm Noise
Zero Scale and Full Scale Set for Reference
and Ground Sensing
Internal Oscillator—No External Components Required
110dB Min, 50Hz/60Hz Notch Filter
Reference Input Voltage: 0.1V to VCC
Live Zero—Extended Input Range Accommodates
12.5% Overrange and Underrange
Pin Compatible with LTC2401/LTC2402
This eliminates the latency found in conventional ∆Σ
converters and simplifies multiplexed applications.
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Through a single pin, the LTC2421/LTC2422 can be
configured for better than 110dB rejection at 50Hz or
60Hz ±2%, or can be driven by an external oscillator for
a user defined rejection frequency in the range 1Hz to
120Hz. The internal oscillator requires no external fre-
quency setting components.
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These converters accept an external reference voltage
from 0.1V to VCC. With an extended input conversion
range of –12.5% VREF to 112.5% VREF (VREF = FSSET
ZSSET), the LTC2421/LTC2422 smoothly resolve the off-
set and overrange problems of preceding sensors or
signal conditioning circuits.
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APPLICATIO S
The LTC2421/LTC2422 communicate through a 2- or
3-wire digital interface that is compatible with SPI and
MICROWIRETM protocols.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency ∆Σ is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
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Weight Scales
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Direct Temperature Measurement
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Gas Analyzers
Strain Gauge Transducers
Instrumentation
Data Acquisition
Industrial Process Control
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Pseudo Differential Bridge Digitizer
TYPICAL APPLICATIO
2.7V TO 5.5V
2.7V TO 5.5V
1
V
CC
1µF
V
CC
= INTERNAL OSC/50Hz REJECTION
1
10
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
LTC2422
SET
V
F
O
CC
LTC2422
2
4
3
5
FS
9
SCK
SDO
CS
2
3
4
5
9
8
7
6
REFERENCE VOLTAGE
ZS + 0.1V TO V
FS
SET
SCK
SDO
CS
8
3-WIRE
SPI INTERFACE
CH0
CH1
ZS
SET
CC
3-WIRE
SPI INTERFACE
ANALOG INPUT RANGE
CH1
CH0
ZS
7
ZS
– 0.12V
TO
SET
FS
REF
+ 0.12V
SET
REF
10
(V
= FS
– ZS
)
REF
SET
SET
F
SET
O
INTERNAL OSCILLATOR
60Hz REJECTION
GND
6
0V TO FS
– 100mV
GND
SET
SET
24212 TA01
24012TA02
24212f
1