CS5529-AP datasheet(15/30 Pages) CIRRUS

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CS5529

DS246F1

Serial Port Initialization

The serial port is initialized to the command mode

whenever a power-on reset is performed or when

the port initialization sequence is completed. The

port initialization sequence involves clocking fif-

teen (or more) SYNC1 command bytes (0xFF) fol-

lowed by one SYNC0 command byte (0xFE). This

sequence places the chip in the command mode

where it waits until a valid command is received.

This function does not reset the internal registers to

their default settings. It only resets the serial port to

the command mode.

System Initialization

When power to the CS5529 is applied, the chip is

held in a reset condition until the 32.768 kHz oscil-

lator has started and a counter-timer elapses. Due to

the high Q of the 32.768 kHz crystal, the oscillator

takes 400-600 ms to start. The counter-timer counts

1002 oscillator clock cycles to make sure the oscil-

lator is fully stable. During this time-out period the

serial port logic is reset and the RV (Reset Valid)

bit in the configuration register is set to indicate

that a valid reset occurred. After a reset, the on-chip

registers are initialized to the following states and

the converter is placed in the command mode

where it waits for a valid command.

Note:

A system reset can be initiated at any time by

writing a logic 1 to the RS (Reset System) bit

in the configuration register. After a reset, the

RV (Reset Valid) bit is set until the

configuration register is read. The user must

then write a logic 0 to the RS bit to take the

part out of the reset mode.

Configuration Register

The configuration register is a 24 bit register used

to modify the functions of the ADC. The following

sections detail the functions of the bits in the con-

figuration register.

Latch Output Pins

The D3-D0 pins of the converter mimic the D21-

D18 bits of the configuration register. D3-D0 can

be used to control multiplexers and other digital

logic functions outside the converter. The D0-D3

outputs are powered from VD+ and DGND. Their

output voltage will be VD+ for a logic 1 and

DGND for a logic 0. The A1-A0 pins of the con-

verter mimic the D23-D22 bits of the configuration

These outputs are powered from VA+ and VA-,

hence, their output voltage will be either VA+ for a

logic 1 or VA- for a logic 0.

All outputs can sink or source at least 1 mA, but it

is recommended to limit drive currents to less than

µA to reduce self-heating of the chip.

Power Consumption

The CS5529 accommodates four power consump-

tion modes: normal, low power, standby, and sleep.

The normal mode, the default mode, is entered after

a power-on-reset and typically consumes 2.5 mW.

The low power mode is an alternate mode that re-

duces the consumed power to 1.4 mW. It is entered

by setting bit D16 (the low power mode bit) in the

configuration register to logic 1. Since the convert-

er’s noise and linearity performance improves with

increased power consumption, slightly degraded

noise or linearity performance should be expected

in the low power mode.

The final two modes are the power save modes.

These modes power down most of the analog por-

tion of the chip and stop filter convolutions. The

power save modes are entered whenever the Power

Save (0x81 hexadecimal) command is issued to the

serial port. The particular power save mode entered

depends on state of bit D4 (the power save select

bit) in the configuration register. If D4 is logic 0,

the converter enters the standby mode reducing the

power consumption to 1 mW. The standby mode

leaves the oscillator and the on-chip bias generator

Configuration Register:

000040(H)

Offset Register:

000000(H)

Gain Register:

400000(H)

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