L99H92 datasheet(11/77 Pages) STMICROELECTRONICS

11 / 77 page

Figure 5. Full-bridge GSHx and GSLx slopes

GADG190920221238SA

VGSyx

y= H, L

x= 1, 2

VDSyx

y= H, L

x= 1, 2

2.6.3

Short circuit detection / drain-source monitoring (DSHS/DSLS)

The voltage-drop over each MOSFET is sensed and compared to a programmable threshold to detect an

overcurrent condition. This monitoring is active only on the MOSFETs driven to be turned on. In dual half-bridge

mode, each half-bridge has its own programmable threshold (DSMONx[2:0]), blanking time (DSBTx[2:0]) and

filtering time (FTx[1:0]). As soon as the gate driver starts to turn on a MOSFET, the corresponding drain source

monitoring comparator output is masked for the programmed blanking time to give time to the MOSFET to turn

on. Besides the blanking time, a filtering time is also present to filter noise. Both values have to be chosen

depending on the application.

If the voltage-drop over the driven MOSFET exceeds the programmed threshold voltage VSCdx (DSMON1[2:0]

control bits for full-bridge or leg 1 and DSMON2[2:0] control bits for leg 2 in dual half-bridge mode) for a time

longer than the programmed filtering time (and the programmed blanking time, where applicable), then:

•

with DSMON_CONFIG control bit set to zero the gate drivers belonging to the faulty leg are forced in sink

switch mode to switch off actively the half-bridge MOSFETs with the maximum available current, regardless

of the programmed gate discharge current (SLEWDx control bits)

•

for INPMODE set to zero and DSMON_CONFIG control bit set to one all the gate drivers are forced in sink

switch mode to switch off actively all the full-bridge MOSFETs.

In any case, the drain source monitoring flag DSHSx or DSLSx of the MOSFET detecting the fault is set. The

drain-source monitoring flags have to be cleared through SPI to reactivate the affected half-bridge/full-bridge gate

drivers that are forced in sink switch mode. The drain-source monitoring flag DSHSx/DSLSx can be cleared by an

SPI “Read & Clear” command only if the fault condition is no longer present.

L99H92

Gate drivers

DS14069 - Rev 4

page 11/77

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