LTC2446/LTC2447
24-Bit High Speed
8-Channel ∆Σ ADCs with
Selectable Multiple Reference Inputs
DESCRIPTION
FEATURES
The LTC®2446/LTC2447 4-terminal switching enables
multiplexed ratiometric measurements. Four sets of
selectable differential inputs coupled with four sets of
differential reference inputs allow multiple RTDs, bridges
and other sensors to be digitized by a single converter.
A fifth differential reference input can be selected for any
input channel not requiring ratiometric measurements
(thermocouples, voltages, current sense, etc.). The flex-
ible input multiplexer allows single-ended or differential
inputs coupled with a slaved reference input or a universal
reference input.
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Five Selectable Differential Reference Inputs
Four Differential/Eight Single-Ended Inputs
4-Way MUX for Multiple Ratiometric
Measurements
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Up to 8kHz Output Rate (External f )
O
Up to 4kHz Multiplexing Rate (External f )
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Selectable Speed/Resolution:
2µV
Noise at 1.76kHz Output Rate
RMS
200nV
Noise at 13.8Hz Output Rate with
RMS
Simultaneous 50/60Hz Rejection
Guaranteed Modulator Stability and Lock-Up
Immunity for any Input and Reference Conditions
0.0005% INL, No Missing Codes
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A proprietary delta-sigma architecture results in absolute
accuracy (offset, full-scale, linearity) of 15ppm, noise as
Autosleep Enables 20µA Operation at 6.9Hz
<5µV Offset (4.5V < V < 5.5V, –40°C to 85°C)
CC
low as 200nV
and speedsas high as 8kHz. Through
RMS
Differential Input and Differential Reference with
a simple 4-wire interface, ten speed/resolution combina-
tions can be selected. The first conversion following a
speed, resolution, channel change or reference change is
valid since there is no settling time between conversions,
enabling scan rates of up to 4kHz. Additionally, a 2× mode
can be selected for any speed-enabling output rates up to
8kHz with one cycle of latency.
GND to V Common Mode Range
CC
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No Latency Mode, Each Conversion is Accurate Even
After a New Channel is Selected
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Internal Oscillator—No External Components
LTC2447 Includes MUXOUT/ADCIN for External
Buffering or Gain
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Tiny QFN 5mm × 7mm Package
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. patents, including 6140950, 6169506, 6208279, 6411242, 6639526.
APPLICATIONS
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Flow
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Weight Scales
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Pressure
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Direct Temperature Measurement
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Gas Chromatography
TYPICAL APPLICATION
LTC2446 RMS Noise vs Speed
100
Multiple Ratiometric Measurement System
V
V
V
= 5V
CC
= 5V
REF
+
–
= V = 0V
IN
IN
2× SPEED MODE
NO LATENCY MODE
V
CC
LTC2446
+
10
1
REF
2.8V AT 880Hz
CS
+
IN
280nV AT 6.9Hz
(50/60Hz REJECTION)
+
–
•
•
•
19-INPUT
4-OUTPUT
MUX
SDI
SDO
SCK
VARIABLE SPEED/
RESOLUTION 24-BIT
–
∆Σ ADC
IN
–
REF
0.1
1
10
100
1000
10000
CONVERSION RATE (Hz)
24467 TA01
24467 TA02
24467fb
1
For more information www.linear.com/LTC2446