5.15.12 CROSS CONDUCTION PROTECTION

Static Cross Conduction Timers

Cross conduction timers at every drive stage prevent switching ON any output driver for a time (tCC ) after the counterpart driver in the same phase has been switched OFF. The cross conduction timers are also active in case a short circuit is detected.

The edge blanking time can be configured as shown in the table below:

Table 5-3. Current Limitation Detection/Short Circuit Detection Time

ILIMFLT [3:0], SCFLT [3:0], EGBLT [3:0]

Blanking/Filter time (ns), typical (±5%)

4’b0000

0

4’b0001

250

4’b0010

500

4’b0011

750

4’b0100

1000

4’b0101

1250

4’b0110

1500

4’b0111

1750

4’b1000

2000

4’b1001

2500

4’b1010

3000

4’b1011

3500

4’b1100

4000

4’b1101

5000

4’b1110

6000

4’b1111

8000

Adaptive Dead-Time Control

The static cross conduction timers can be replaced by adaptive dead-time control. The adaptive dead-time comparators monitor voltages on the gate drive outputs and switch node to determine when to switch the MOSFETs ON and OFF.

To prevent cross conduction when turning ON high side switches, the ATA6847 monitors the low side MOSFETs gate source voltage (VGLx – VSL(ATA6847L) or VGND(ATA6847) ) and prevents turning ON the high side MOSFET in the same branch until the gate source voltage of the low-side switch is lower than VLOOFF.

To prevent cross conduction when switching ON low-side switches, the ATA6847 monitors the voltage on the SHx switching node. The low-side gate drive can only be switched on when the SHx switching node voltage drops below VSWTH. Once the low-side gate drive is switched on, it is latched until the NIHx signal goes low. This prevents any ringing or oscillations on the switch node or the SHx pin from turning OFF the GSx driver. If the NIHx pin goes high and the voltage on the SHx pin does not cross the VSWTH threshold, the low-side gate drive is deactivated automatically after the Adaptive Deadtime Force To Switch Delay Time (tSWTO) has passed.