LM4921

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SNAS178E – JULY 2003 – REVISED MAY 2013

ZERO CROSSING DETECT SET

This pin turns on the zero crossing detection circuit. With this circuit enabled the part will not allow a volume step

change, or shutdown mode, or standby mode to occur until the audio input signal passes through zero. This pin

should be set to on for most applications.

VOLUME CONTROL

The internal Stereo Volume Control is set by changing bits 7 through 11 in the SPI interface, as shown in Table 3

below. The zero dB setting is for 3V VDD operation and the +3dB is for 5V VDD.

Table 3. Volume Control Settings

Gain (dB)

Bit 11

Bit 10

Bit 9

Bit 8

Bit 7

HP_L & HP_R

-43.5

0

0

0

0

0

-42.0

0

0

0

0

1

-40.5

0

0

0

1

0

-39.0

0

0

0

1

1

-37.5

0

0

1

0

0

-36.0

0

0

1

0

1

-34.5

0

0

1

1

0

-33.0

0

0

1

1

1

-31.5

0

1

0

0

0

-30.0

0

1

0

0

1

-28.5

0

1

0

1

0

-27.0

0

1

0

1

1

-25.5

0

1

1

0

0

-24.0

0

1

1

0

1

-22.5

0

1

1

1

0

-21.0

0

1

1

1

1

-19.5

1

0

0

0

0

-18.0

1

0

0

0

1

-16.5

1

0

0

1

0

-15.0

1

0

0

1

1

-13.5

1

0

1

0

0

-12.0

1

0

1

0

1

-10.5

1

0

1

1

0

-9.0

1

0

1

1

1

-7.5

1

1

0

0

0

-6.0

1

1

0

0

1

-4.5

1

1

0

1

0

-3.0

1

1

0

1

1

-1.5

1

1

1

0

0

0.0

1

1

1

0

1

1.5

1

1

1

1

0

3.0

1

1

1

1

1

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