LTC2424/LTC2428
4-/8-Channel 20-Bit µPower
No Latency ∆ΣTM ADCs
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FEATURES
DESCRIPTIO
The LTC®2424/LTC2428 are 4-/8-channel 2.7V to 5.5V
micropower 20-bit A/D converters with an integrated
oscillator, 8ppm INL and 1.2ppm RMS noise. They use
delta-sigma technology and provide single cycle digital
filter settling time (no latency delay) for multiplexed
applications. The first conversion after the channel is
changedisalwaysvalid.ThroughasinglepintheLTC2424/
LTC2428 can be configured for better than 110dB rejec-
tion at 50Hz or 60Hz ±2%, or can be driven by an external
oscillator for a user defined rejection frequency in the
range 1Hz to 800Hz. The internal oscillator requires no
external frequency setting components.
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Pin Compatible 4-/8-Channel 20-Bit ADCs
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8ppm INL, No Missing Codes at 20 Bits
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4ppm Full-Scale Error and 0.5ppm Offset
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1.2ppm Noise
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Digital Filter Settles in a Single Cycle. Each
Conversion is Accurate, Even After Changing
Channels
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Fast Mode: 16-Bit Noise, 12-Bit TUE at 100sps
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Internal Oscillator—No External Components
Required
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110dB Min, 50Hz/60Hz Notch Filter
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Reference Input Voltage: 0.1V to VCC
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Live Zero—Extended Input Range Accommodates
The converters accept any external reference voltage from
0.1VtoVCC. Withtheirextendedinputconversionrangeof
–12.5% VREF to 112.5% VREF (VREF = FSSET – ZSSET) the
LTC2424/LTC2428 smoothly resolve the offset and
overrange problems of preceding sensors or signal con-
ditioning circuits.
12.5% Overrange and Underrange
Single Supply 2.7V to 5.5V Operation
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Low Supply Current (200µA) and Auto Shutdown
Can Be Interchanged with 24-Bit LTC2404/LTC2408
■
if ZSSET Pin is Grounded
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APPLICATIO S
The LTC2424/LTC2428 communicate through a flexible
4-wire digital interface which is compatible with SPI and
MICROWIRETM protocols.
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Weight Scales
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Direct Temperature Measurement
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Gas Analyzers
Strain-Gage Transducers
Instrumentation
Data Acquisition
Industrial Process Control
4-Digit DVMs
No Latency ∆Σ is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
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TYPICAL APPLICATIO
Total Unadjusted Error (3V Supply)
10
V
V
= 3V
REF
0.1V TO V
CC
CC
2.7V TO 5.5V
8
6
= 2.5V
7
4
3
2, 8
1µF
MUXOUT
ADCIN
FS
SET CC
V
SERIAL DATA LINK
MICROWIRE AND
SPI COMPATABLE
9
CH0
4
23
20
25
19
21
24
10 CH1
11 CH2
12 CH3
13 CH4*
14 CH5*
15 CH6*
17 CH7*
CSADC
2
CSMUX
SCK
0
ANALOG
INPUTS
20-BIT
∆Σ ADC
4-/8-CHANNEL
MUX
+
–2
–4
–6
–8
–10
MPU
CLK
–0.12V
TO
REF
1.12V
D
IN
REF
–
T = –55°C, –45°C, 25°C, 90°C
A
SDO
V
CC
LTC2424/LTC2428
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
5
ZS
SET
26
F
O
GND
0
0.5
1.0
1.5
INPUT VOLTAGE (V)
2.0
2.5
24248 TA01
1, 6, 16, 18, 22, 27, 28
*THESE PINS ARE NO CONNECTS ON THE LTC2404
24248 G01
1