Cirrus Logic CRD5376 - Manual (Page 19)

CRD5376
DS612RD2 19
2.2.5.1 VREF_MOD12, VREF_MOD34, VREF_DAC
The voltage reference output is provided to the CS5372A ∆Σ modulators and the CS4373A test DAC
through separate low pass RC filters. By separately filtering the voltage reference for each device, signal
dependent sampling of VREF by one device is isolated from other devices. Each voltage reference signal
is routed as a separate differential pair from the large RC filter capacitor to control the sensitive VREF
source-return currents and keep them out of the ground plane. In addition to the RC filter function, the
100 uF filter capacitor provides a large charge-well to help settle voltage reference sampling transients.
2.3 Digital Hardware
2.3.1 Digital Filter
The CS5376A quad digital filter performs filtering and decimation of four delta-sigma bit streams from the
CS5372A modulators. It also creates a delta-sigma bit stream output to create analog test signals in the
CS4373A test DAC.
The CS5376A requires several control signal inputs from the external system.
Configuration is completed through the SPI 1 port.
Control Signals Description
RESETz Reset input, active low
BOOT Microcontroller / EEPROM boot mode select
TIMEB Time Break input, rising edge triggered
CLK Master clock input, 32.768 MHz
SYNC Master synchronization input, rising edge triggered
SPI1 Signals Description
SSIz Serial chip select input, active low
SCK1 Serial clock input
MISO Master in / slave out serial data
MOSI Master out / slave in serial data
SINTz Serial acknowledge output, active low
SSOz Serial chip select output (unused on CRD5376)