SABRE-LL-I datasheet(23/141 Pages) STMICROELECTRONICS

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SABRE-LL-I

Supervisory system

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5.5

Thermal shut down generation circuit

The third component of the supervisory circuit is the thermal shut down generation circuit.

This circuit generates two different flags depending on the IC temperature:

–

the “TSD” flag indicates that the IC temperature is greater than the maximum

allowable temperature.

–

the “Warm” flag, that can be read using serial interface, becomes active at a lower

temperature respect to TSD signal, therefore it can be used to prevent the IC from

reaching over temperature.

When a TSD event occurs, S.A.B.Re will enter in the reset state placing the bridges in high

impedance and turning off all regulators and other circuits until the internal temperature

decreases below the Warm temperature. At this point, S.A.B.Re will restart the power up

sequence and TSD bit will be set and will be readable as soon as S.A.B.Re will come out

from the reset state.

This TSD bit can be reset in three ways:

–

by writing a logic level ‘1’ in the ClearTSD bit in the ICTemp register (see

Chapter 25);

–

by a POR event;

–

by entering in “Low Power Mode”.

The Warm bit, set by S.A.B.Re when IC is working over the warming temperature, can be

read using the SPI interface. Once this bit is set it can be reset in three ways:

–

by writing a logic level ‘1’ in the ClearWarm bit;

–

by a POR event;

–

by entering in “Low Power Mode”.

The thermal sensor voltage can be converted using the internal A/D: this way the

microcontroller can directly measure the IC temperature.

To avoid unwanted commutation especially when temperature is near the thresholds, the

output signal is filtered for both TSD and Warm.

5.6

TSD specifications

Table 10.

TSD circuit specifications

Parameter

Description

Test

condition

Min

Typ

Max

Unit

TTSD

Thermal shut down temperature

170

°C

TWARM

Warming temperature

140

°C

TDIFF

Thermal shut down to warming

difference

°C

tTSD_FILT

Thermal shut down filter time

tWARM_FILT

Warming filter time

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