Datasheet LTC2446, LTC2447 (Analog Devices)

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