STA381BWS datasheet(94/171 Pages) STMICROELECTRONICS

94 / 171 page

STA381BWS

94/171

Doc ID 018937 Rev 6

6.32

Enhanced zero-detect mute and input level measurement

(address 0x61-0x65, 0x3F, 0x40, 0x6F)

The STA381BWS implements an RMS-based zero-detect function (on serial input interface

data) able to detect in a very reliable way the presence of an input signal, so that the power

bridge outputs can be automatically connected to ground.

When active, the function will mute the output PWM when the input level becomes less than

“threshold - hysteresis”. Once muted, the PWM will be unmuted when the input level is

detected greater than “threshold + hysteresis”.

The measured level is then reported (for each input channel) on registers ZCCCFG1 -

ZCCCFG2, ZCCCFG3 - ZCCCFG4 according to the following equation:

Value_in_dB = 20*Log10(Reg_value/(2

16*0.635))

WTHH

WTHL

FINETH

HSEL[1:0]

ZMTH[2:0]

RMS_CH0[7:0]

N/A

RMS_CH0[15:8]

N/A

RMS_CH1[7:0]

N/A

RMS_CH1[15:8]

N/A

Table 88.

Zero-detect threshold

ZMTH[2:0]

Equivalent input level (dB)

000

-78

001

-84

010

-90

011

-96

100

-102

101

-108

110

-114

111

-114

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