L99H92 datasheet(12/77 Pages) STMICROELECTRONICS

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Figure 6. Full-bridge drain-source monitoring diagnosis

GADG120920220932SA

VDH

GH1

VDH

SH1

GL1

VDH

GH2

SH2

GL2

20k

Gate Driver HS

Gate Driver LS

DS-Monitoring HS

DS-Monitoring LS

OL-Monitoring

VSCd

20k

Gate Driver HS

Gate Driver LS

DS-Monitoring HS

DS-Monitoring LS

OL-Monitoring

VSCd

SL1

SL2

2.6.4

Programmable cross current protection time (DT)

In any input mode (dual half-bridge mode or full-bridge mode), the device automatically adds a dead-time

between the turn-off of a MOSFET and the turn-on of the complementary one (that is, the other MOSFET of the

same leg) to avoid cross-conduction in any of the half-bridges.

In dual half-bridge mode, each half-bridge dead-time tDT (from tDT0000 to tDT1111) is independently configurable by

control bits DT1[3:0] and DT2[3:0]. Instead, in full-bridge mode, the dead time of both half-bridges is set by control

bits DT1[3:0].

2.7

Diagnostic in off-mode (O1DS/O2DS)

Two off-state diagnostic comparators compare the drop between each half-bridge output (SHx pin) and related LS

MOSFET source (SLx) to a programmable threshold , while all the transistors are switched off. Possible system

faulty conditions such as open-load, output shorted to ground or to battery, before even turning on any of the

MOSFETs can be so detected.

The outputs of the off-state diagnostic comparators are always available (except in standby mode) and can be

read through O1DS and O2DS status bits of the status register DSR2.

When the OUTE control bit set, the O1DS and the O2DS status bits provide the not filtered SH1 and SH2 output

logic levels respect to the threshold, selected by the DSMONxy control bits, respectively. In all the other cases

(except in standby mode, where everything is disabled) the O1DS and the O2DS status bits provide the not

filtered SH1 and SH2 output logic levels respect to the threshold, selected by the OLTHH control bit, respectively.

To run off-state diagnostic the device has to be in off-state diagnostic mode.

To enter in off–state diagnostic mode at least the OLH1L2 control bit or the OLH2L1 control bit has to be set to

one with the device OUTE control bit set to zero and CSA must be disabled. To exit from off–state diagnostic

mode either the OUTE control bit is set to one or both the OLH1L2 and the OLH2L1 are set to zero. In off–state

diagnostic mode a pull-up resistor is connected to one of the half-bridge outputs or to both and two pull-down

resistors are connected to the two half-bridge outputs.

Considering that the pull-up resistance is the same as the pull-down resistances, the VDS of the two low side

transistors (that is, the two half-bridge outputs) is expected to be equal to 1/3 VDH if a low resistive load is

connected between the two legs.

On the contrary if the VDS of any of the two low sides is lower than 1/6 VDH (OLTHH=0) or higher than 5/6 VDH

(OLTHH=1), then a faulty condition must be present.

Below figures and table summarize the possible faulty conditions and related OxDS status bits values.

L99H92

Diagnostic in off-mode (O1DS/O2DS)

DS14069 - Rev 4

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