CS5376-BS データシートの表示（PDF） - Cirrus Logic

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CS5376-BS

Low Power Multi-Channel Decimation Filter

Cirrus Logic 

CS5376

3rd order infinite impulse response filter with any

corner frequency in the measurement bandwidth.

A set of on-chip FIR and IIR coefficients are in-

cluded in the CS5376 to provide an easy set up for

applications that do not require custom filter coef-

ficients. These coefficients have excellent filtering

characteristics, with the low-pass FIR filters having

a corner frequency at 40% fs, in-band ripple less

than ±0.01 dB, and stop-band attenuation greater

than 130 dB. The high-pass IIR filter provides a 3rd

order Butterworth response with a corner frequen-

cy at 2% fs.

Programmable Gain and Offset Correction

The final operation of the digital filter is to apply a

user defined gain and offset correction to the output

data. The gain correction value is independently

programmable for each channel and is used to nor-

malize sensor gain across a network. Similarly, the

offset correction is independently programmable

for each channel and is used to correct for DC off-

set in a sensor. The CS5376 also includes a built in

offset calibration routine that will calculate offset

correction values automatically.

2.3 Integrated Hardware Peripherals

High Speed Serial Data Output Port

After filtering is completed, each 24-bit output

sample is combined with an 8-bit status word that

encodes the channel number, a time break flag, and

any error conditions. This 32-bit data word is writ-

ten to an 8-deep FIFO buffer and then transmitted

on request to the communications interface through

the high speed serial data output port. In a typical

system, the communication interface will be a pro-

prietary design.

Test Bit Stream Generator

The CS5376 includes a programmable test bit

stream (TBS) generator that produces a 1-bit ∆−Σ

modulated bitstream with 24-bits of precision, suit-

able for driving a test DAC to verify the analog per-

formance of the conversion channel. The TBS

generator also includes an internal digital loopback

option so the digital filters and communication in-

terface can be tested independently of the analog

circuitry. The TBS generator can easily be pro-

grammed to produce a number of test signals using

the included 1024 point sine wave data table. By

writing a single configuration register many com-

mon test frequencies can be generated, including

31.25 Hz, 50.0 Hz, and 125.0 Hz. Custom test sig-

nal frequencies can be generated by writing a new

sine wave data table.

Secondary SPI Port

A secondary master mode SPI 2 port allows serial

peripherals to be controlled through the primary

SPI 1 port. The CS5376 acts as an arbiter to con-

duct transactions between the communications in-

terface connected to the primary SPI 1 port and

serial peripherals connected to the secondary SPI 2

port. This simplifies system design by requiring

only one SPI connection to the communication in-

terface to control the CS5376 and multiple serial

peripherals.

General Purpose I/O Pins

Twelve general purpose I/O pins on the CS5376

can be used for local hardware control or as chip se-

lects for the SPI ports. These pins are independent-

ly programmable as inputs or outputs, with or

without an internal pull-up resistor.

JTAG Test Port

The CS5376 includes a standard IEEE 1149.1

JTAG test port for system level testing via bound-

ary scan.

Clock and Synchronization Block

A clock and synchronization block in the CS5376

establishes synchronous timing when used in a dis-

tributed measurement network. An input SYNC

signal from the host system resets the modulator

DS256PP1

10

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