1
LTC2424/LTC2428
4-/8-Channel 20-Bit µPower
No Latency ∆Σ
TM
ADCs
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
changed is always valid. Through a single pin the LTC2424/
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.
The converters accept any external reference voltage from
0.1V to V
CC
. With their extended input conversion range of
–12.5% V
REF
to 112.5% V
REF
(V
REF
= FS
SET
– ZS
SET
) the
LTC2424/LTC2428
smoothly resolve the offset and
overrange problems of preceding sensors or signal con-
ditioning circuits.
The
LTC2424/LTC2428
communicate through a flexible
4-wire digital interface which is compatible with SPI and
MICROWIRE
TM
protocols.
■
Pin Compatible 4-/8-Channel 20-Bit ADCs
■
8ppm INL, No Missing Codes at 20 Bits
■
4ppm Full-Scale Error and 0.5ppm Offset
■
1.2ppm Noise
■
Digital Filter Settles in a Single Cycle. Each
Conversion is Accurate, Even After Changing
Channels
■
Fast Mode: 16-Bit Noise, 12-Bit TUE at 100sps
■
Internal Oscillator—No External Components
Required
■
110dB Min, 50Hz/60Hz Notch Filter
■
Reference Input Voltage: 0.1V to V
CC
■
Live Zero—Extended Input Range Accommodates
12.5% Overrange and Underrange
■
Single Supply 2.7V to 5.5V Operation
■
Low Supply Current (200µA) and Auto Shutdown
■
Can Be Interchanged with 24-Bit LTC2404/LTC2408
if ZS
SET
Pin is Grounded
Total Unadjusted Error (3V Supply)
, 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.
■
Weight Scales
■
Direct Temperature Measurement
■
Gas Analyzers
■
Strain-Gage Transducers
■
Instrumentation
■
Data Acquisition
■
Industrial Process Control
■
4-Digit DVMs
ANALOG
INPUTS
–0.12V
REF
TO
1.12V
REF
24248 TA01
CH0
CH1
CH2
CH3
CH4*
CH5*
CH6*
CH7*
9
10
11
12
13
14
15
17
+
–
4-/8-CHANNEL
MUX
5ZS
SET
*THESE PINS ARE NO CONNECTS ON THE LTC2404
GND
1, 6, 16, 18, 22, 27, 28
MPU
SERIAL DATA LINK
MICROWIRE AND
SPI COMPATABLE
23
20
25
19
21
24
CSADC
CSMUX
SCK
CLK
D
IN
SDO
26
F
O
20-BIT
∆Σ ADC
LTC2424/LTC2428
0.1V TO V
CC
ADCINMUXOUT
7 4 3 2, 8
1µF
2.7V TO 5.5V
FS
SET
V
CC
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
V
CC
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
INPUT VOLTAGE (V)
0
ERROR (ppm)
2
6
10
2.0
24248 G01
–2
–6
0
4
8
–4
–8
–10
0.5
1.0
1.5
2.5
V
CC
= 3V
V
REF
= 2.5V
T
A
= –55°C, –45°C, 25°C, 90°C
