TIDA-01605: Desat protection Circuit blanking time problem

Damith Warahenage

Part Number: TIDA-01605

What is the purpose of the D8 in this circuit.
Because if the C34 is there for the blanking time, then after the first gate pulse, C34 will be charged and there is no way to discharge it other than the reset signal.
If there is no reset signal, this capacitor voltage will reach up to 5.1 V and trigger the comparator.
In order to handle that, there should be a reset pulse just after the gate pulse.
This circuit seems to be incomplete.

Regards

Damith

5 months ago

0 Shaurya Sharma 4 months ago

TI__Prodigy 20 points

Hi Damith,

D8: it is used to create the required voltage drop, as given in equation 14.

Reset function: as given in the schematic file (https://www.ti.com/lit/pdf/tidrvt3) , could be seen there OUTB (ISO7721QDRQ1) signal enables 'Reset' through Q3, giving a discharge path for C34.

Best regards,

Shaurya

0 Damith Warahenage 4 months ago in reply to Shaurya Sharma

Prodigy 70 points

Thanks

That diode must be there for another purpose other than voltage drop.

If the reset is done like that, Then there should be a separate reset pulse at the start of each and every gate pulse, which seems to be unusual.

0 Shaurya Sharma 4 months ago in reply to Damith Warahenage

TI__Prodigy 20 points

Hi,

The diode prevents the capacitor C34 to discharge with another path (through R26). Once overshoot is detected (capacitor charged) it will hold the fault until the reset signal is sent. Only via reset signal the discharge circuit is activated and the capacitor can be discharged.

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TIDA-01605: Desat protection Circuit blanking time problem