LTC1598CG-TR Ver la hoja de datos (PDF) - Linear Technology

Número de pieza

componentes Descripción

Fabricante

LTC1598CG-TR

4- and 8-Channel, Micropower Sampling 12-Bit Serial I/O A/D Converters

Linear Technology 

LTC1594/LTC1598

TYPICAL APPLICATIONS N

MULTICHANNEL A/D USES A SINGLE ANTIALIASING

FILTER

This circuit demonstrates how the LTC1598’s indepen-

dent analog multiplexer can simplify design of a 12-bit

data acquisition system. All eight channels are MUXed into

a single 1kHz, 4th order Sallen-Key antialiasing filter,

which is designed for single supply operation. Since the

LTC1598’s data converter accepts inputs from ground to

the positive supply, rail-to-rail op amps were chosen for

the filter to maximize dynamic range. The LT1368 dual rail-

to-rail op amp is designed to operate with 0.1μF load

capacitors (C1 and C2). These capacitors provide fre-

quency compensation for the amplifiers and help reduce

the amplifier’s output impedance and improve supply

rejection at high frequencies. The filter contributes less

than 1LSB of error due to offsets and bias currents. The

filter’s noise and distortion are less than –72dB for a

100Hz, 2VP-P offset sine input.

The combined MUX and A/D errors result in an integral

nonlinearity error of ± 3LSB (maximum) and a differential

nonlinearity error of ±3/4LSB (maximum). The typical

signal-to-noise plus distortion ratio is 71dB, with approxi-

mately –78dB of total harmonic distortion. The LTC1598

is programmed through a 4-wire serial interface that is

compatable with MICROWIRE, SPI and QSPI. Maximum

serial clock speed is 320kHz, which corresponds to a

16.8kHz sampling rate.

The complete circuit consumes approximately 800μA

from a single 5V supply.

Simple Data Acquisition System Takes Advantage of the LTC1598’s

MUXOUT/ADCIN Pins-to-Filter Analog Signals Prior to A/D Conversion

ANALOG INPUTS

0V TO 5V

RANGE

1 CH5

CH4 24

2 CH6

CH3 23

3 CH7

CH2 22

4 GND

CH1 21

5 CLK LTC1598 CH0 20

6 CSMUX

7 DIN

8 COM

VCC 19

MUXOUT 18

ADCIN 17

9 GND

10 CSADC

11 DOUT

12 NC

VREF 16

VCC 15

CLK 14

NC 13

5V

1μF

1/2

LT1368

C2

5V

0.1μF

1μF

7.5k

DATA OUT

DATA IN

CHIP SELECT

CLOCK

7.5k

0.015μF

0.03μF

7.5k

+

1/2

LT1368

–

0.015μF

7.5k

0.03μF

C1

0.1μF

1594/98 TA05

15948fb

21

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