L9912TR datasheet(29/84 Pages) STMICROELECTRONICS

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L9912

Electrical specifications

5.3.10

Pin "DRAIN" and "SOURCE"

The device monitors the voltage between pins DRAIN and SOURCE in order to provide

short circuit protection to the external Power MOS.

When the gate-to-source voltage exceeds the VGSth value, the monitoring of the drain-to-

source voltage becomes active and in case the voltage drop over the external power MOS

exceeds the threshold voltage VSCdx the gate driver will automatically switch the external

MOS transistor off and the corresponding drain-to-source monitoring flag will be set in the

SPI (bit 9 of read register 0x12 [13.4.6]). In order to turn the external MOS driver back on,

the µC needs to read (and then clear) the diagnostic bit.

Figure 9. External MOS short circuit protection

The threshold voltage VSCdx can be programmed in 4 steps between 0.5 V and 2 V with the

SPI (write register 0x03).

The drain source monitoring has a filter time Tscfilter and is only active when the

corresponding gate driver is in source condition.

Table 20. Electrical characteristics pin "DRAIN" and "SOURCE"

Symbol

Parameter

Test condition

Min.

Typ.

Max.

Unit

1VSCd1

Drain-to source voltage

threshold 1

-0.4

0.5

0.6

2VSCd2

Drain-to source voltage

threshold 2

-0.9

1.0

1.1

3VSCd3

Drain-to source voltage

threshold 3

1.35

1.5

1.65

4VSCd4

Drain-to source voltage

threshold 4

-1.8

2.0

2.2

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