CS4294 datasheet(35/42 Pages) CIRRUS

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CS4294

DS326PP4

BCM# - BIT_CLK Mode, Input

This pin selects the secondary mode clocking mechanism. BCM# is sampled after the rising

edge of RESET# and not used after. In codec secondary mode (ID1# and or ID0# grounded),

grounding this input will select BIT_CLK mode. In this mode, BIT_CLK is defined as an input

and all internal timing will be derived from the BIT_CLK signal and no connections should be

made to XTAL_IN and XTAL_OUT. When BCM# is floating, all timing will be derived from

the XTAL_IN pin. In this case, XTAL_IN must be synchronous to BIT_CLK. In primary mode,

BCM# must be left floating.

GPIO[8:3] - General Purpose Input/Output

These GPIO pins are used to control discrete digital functions. When a GPIO pin is configured

as an input, it behaves as a Schmitt trigger input with 350 mV of hysteresis at 5 V and 220 mV

of hysteresis at 3.3 V. When a GPIO pin in configured as an output, it may function as a

normal CMOS output (4 mA drive) or as an open drain output. GPIO pins power up in the high

impedance state (tri-state).

8.2

Analog I/O Pins

MIC1 - Analog Mono Source, Input

This analog input is a monophonic source to the analog output mixer. It is intended to be used

as a desktop microphone connection to the audio subsystem. The maximum allowable input is

1VRMS (sinusoidal). If the 20 dB internal boost is enabled, the maximum allowable input is

100 mVRMS (sinusoidal). This input is internally biased at the Vrefout voltage reference and

requires AC coupling to external circuitry. If this input is not used, it should be AC coupled to

analog ground.

LINE_IN_L and LINE_IN_R- Analog Line Source, Inputs

These inputs form a stereo input pair to the CS4294. The maximum allowable input is

1VRMS (sinusoidal). These inputs are internally biased at the Vrefout voltage reference. AC

coupling to external circuitry is required. If these inputs are not used, they should both be

connected to the Vrefout pin or both AC coupled, with separate AC coupling caps, to analog

ground.

CD_L and CD_R - Analog CD Source, Inputs

These inputs form a stereo input pair to the CS4294. It is intended to be used for the Red Book

CD audio connection to the audio subsystem. The maximum allowable input is 1 VRMS

(sinusoidal). These inputs are internally biased at the Vrefout voltage reference. AC coupling to

external circuitry is required. If these inputs are not used, they should both be connected to the

Vrefout pin or both AC coupled, with separate AC coupling caps, to analog ground.

CD_GND - Analog CD Common Source, Input

This analog input is used to remove common mode noise from Red Book CD audio signals.

The impedance on the input signal path should be one half the impedance on the CD_L and

CD_R input paths. This pin requires AC coupling to external circuitry. If this input is not used,

it should be connected to the Vrefout pin or AC coupled to analog ground.

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