STA309B datasheet(60/66 Pages) STMICROELECTRONICS

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Equalization and mixing

STA309B

60/66

Doc ID 022570 Rev 2

8.4

PSCorrect registers

ADC is used to input ripple data to SDI78. The left channel (7) is used internally. No audio

data can therefore be used on these channels, although all channel mapping and mixing

from other inputs to channels 7 and 8 internally are still valid.

8.4.1

PSC1-2: ripple correction value (RCV) (0x51, 0x52)

This function is equivalent to the negative maximum ripple peak as a percentage of Vcc

(MPR), scaled by the inverse of the maximum ripple p-p as a percentage of full-scale analog

input to ADC. It is represented as a 1.11 signed fractional number.

8.4.2

PSC3: correction normalization value (CNV) (0x53)

This function is equivalent to 1 / (1+MPR) expressed as a 0.12 unsigned fractional number.

8.5

Digital pop-free operation in single-ended mode

The STA309B pop-free feature allows digitally pre-loading the bypass capacitor between the

filtered amplifier output and the load in single-ended applications. Normally, a bypass

capacitor needs to be preloaded to half of the power supply in order to avoid having pop-

noise at PWM startup.

By enabling the STA309B pop-free feature, it is possible to preload the capacitor using the

amplifier, without needing the resistive partition. By forcing a ramp, it is possible to gradually

load the capacitor from zero to half the supply with the PWM signal starting from near 0%

duty cycle to 50% duty cycle. This “active load” is also faster than the resistive partition

method.

RCV11

RCV10

RCV9

RCV8

RCV7

RCV6

RCV5

RCV4

RCV3

RCV2

RCV1

RCV0

CNV11

CNV10

CNV9

CNV8

CNV7

CNV6

CNV5

CNV4

CNV3

CNV2

CNV1

CNV0

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