TDA7572 datasheet(54/64 Pages) STMICROELECTRONICS

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Under voltage lock out (UVLO)

TDA7572

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Under voltage lock out (UVLO)

The UVLO lock at the voltage references value used to run the device. If some of them are

not in the rate band the system is put in tristate or in stand-by. The Auto-mute Voltage

Setting pin (pin56) voltage is used to define the limits of this voltage references.

List of monitored pin:

MODE0 and MODE1 voltage value

VSP-VSM voltage difference

SVR voltage value

VSP-SVR or VSR-VSM voltage difference

V14 voltage value

In the UVLO could be defined four blocks:

–

VSP - UVLO

–

VP2.5/VM2.5 UVLO

–V14 - UVLO

–SVR - UVLO

12.1

VSP-UVLO

This block monitors the VSP-VSM drop and eventually moves the modulator in mute or in

tristate. The limits imposed by the VSP-UVLO block are principally three:

an adjustable limit on the minimum supply/drop

an adjustable limit on the maximum supply/drop

an absolute limit on the maximum supply

The adjustable limits are obtained by means of the reference voltage present on the

AutomuteVSetting pin, which is fixed by means of a ladder resistor of R1 and R2 between

VP2.5 and SVR.

The comparators that sense the voltage drop for the auto mute are provided of hysteresis.

An hysteresis is still present for the auto-tristate and expressed in the spec as two different

thresholds that are function of reference voltage and slope polarity.

12.2

V14 - UVLO

This block monitors the V14-VSM drop voltage and eventually moves the modulator in mute

or in tristate. The V14-UVLO block fixes a limit on the minimum drop.

An hysteresis is present for the auto-tristate and expressed in the spec as two different

thresholds that are function of slope polarity. An hysteresis is still present for the auto-mute

and expressed in the spec as two different thresholds that are function of auto-tristate

threshold and slope polarity.

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