L99DZ120 datasheet(91/162 Pages) STMICROELECTRONICS

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L99DZ120

Application information

161

4.28

Programmable cross current protection

The external PowerMOSFETs transistors in H-bridge (two half-bridges) configuration are

switched on with an additional delay time tCCP to prevent cross current in the halfbridge. The

cross current protection time tCCP can be programmed with the SPI bits COPT_x<3:0>

(CR 10). The timer is started when the gate driver is switched on in the device.

The PWMH module has 2 timers to configure locking time for high-side and freewheeling

low-side. The programmable time tCCP-TIM1 / tCCP-TIM2 is the same. Sequence for switching

in PWM mode is the following:



HS switch off after locking tCCP-TIM1



LS switch on after 2nd locking tCCP-TIM1



HS switch on after locking tCCP-TIM2 which starts with rising edge on PWM input

Figure 43. PWMH cross current protection time implementation

4.29

Power window H-bridge safety switch off block

The two LS Switches LS1_FSO and LS2_FSO are intended to be used to switch off the

gates of the external high-side MOSFETs in the power window h-bridge if a fatal error

happens. This block must work also in case the MOSFET driver and the according control

blocks on the chip are destroyed. Therefore it is necessary to have a complete separated

safety block on the device, which has it’s own supply and GND connection, separated from

the other supplies and GNDs. In the block is implemented an own voltage regulator and

oscillator.

Short to GND

Short to VS

Table 50. H-bridge monitoring in off-mode (continued)

Control bits

Failure bits

Comments

Nb OL H1L2 OL H2L1 H OLTH High DSMON LS1 DSMON LS2

L99DZ120 Datasheet(PDF) 91 Page - STMicroelectronics