Figure 8. VBO power-ON and UVLO timing

VCC

VCCthON

VCCthOFF

0 V

0 V

FAULT

HIN

HVG-OUT

BOthON

VBOthOFF

0 V

V

VBO

0 V

0 V

5.5

Comparator and smart shutdown

This device integrates a comparator committed to the fault protection function, thanks to the SmartShutDown

(SmartSD) circuit.

The SmartSD architecture allows immediate turn-off of the gate driver outputs in the case of overload or

overcurrent condition, by minimizing the propagation delay between the fault detection event and the actual

output switch-off. In fact, the time delay between the fault detection and the output turn-off is not dependent on the

value of the external components connected to the OD pin, which are only used to set the duration of disable time

after the fault.

This provides the possibility to increase the duration of the output disable time after the fault event up to very

large values without increasing the delay time of the protection. The duration of the disable time is determined by

the values of the external capacitor COD and of the optional pull-up resistor connected to OD pin.

The comparator has an internal voltage reference VREF connected to the inverting input, while the non-inverting

input is available on the CIN pin. The comparator CIN input can be connected to an external shunt resistor in

order to implement a fast and simple overcurrent protection function. The output signal of the comparator is

filtered from glitches shorter than tFCIN and then fed to the SmartSD logic.

If the impulse on CIN pin is higher than VREF and wider than tFCIN, the SmartSD logic is triggered and

immediately sets all of the driver outputs to low-level (OFF).

At the same time, FAULT is forced low to signal the event (for example to an MCU input) and OD starts to

discharge the external COD capacitor used to set the duration of the output disable time of the fault event.

The FAULT pin is released and driver outputs restart following the input pins as soon as the output disable time

expires.

The overall disable time is composed of two phases:

•

The OD unlatch time (t1 in Figure 9. Smart shutdown timing waveforms), which is the time required to

discharge COD capacitor down to VSSDl threshold. The discharge starts as soon as the SmartSD comparator

is triggered.

•

The OD restart time (t2 in Figure 9. Smart shutdown timing waveforms, which is the time required to

recharge the COD capacitor up to the VSSDh threshold. The recharge of COD starts when the OD internal

MOSFET is turned-off, which happens when the fault condition has been removed (CIN < VREF - CINhyst)

and the voltage on OD reaches the VSSDl threshold. This time normally covers most of the overall output

disable time.

STDRIVE601

Comparator and smart shutdown

DS12949 - Rev 2

page 14/26