UCC21710-Q1: Impedance of OC pin

Mamoru Sasaki

Part Number: UCC21710-Q1
Other Parts Discussed in Thread: UCC21710

Hello,

I'm using UCC21710 and would like to utilize OC pin for overcurrent protection.

Since I have a current sensor on the low voltage side, I am using a digital isolator to transmit overcurrent signal to OC pin. In this case, can I connect the output of the digital isolator to OC pin directly?

As I read "8.3.7 Overcurrent and Short Circuit Protection" of the data sheet, I found that the OC pin is high-Z only when the output is high. Thus, I'm wondering if I need resister between the digital isolator and OC pin to avoid large current flows into OC pin.

If I don't need the current limiting resister, what would happen when the output is low and OC pin is pulled to high?

Thank you.

Mamoru

4 months ago

0 Sasikala Thangam 4 months ago

TI__Expert 6520 points

Hi Mamoru,

The OC pin's internal pull down current typical is 40 mA per the datasheet spec at 1V, so its internal impedance is 25 ohms. The max voltage level on OC pin has to be 5V. So please ensure that the current and voltage levels are not violated based on your external circuit.

Hope it helps.

Thanks

Sasi

0 Mamoru Sasaki 4 months ago in reply to Sasikala Thangam

Prodigy 20 points

Hi Sasi,

Thank you for the reply. I will be careful not to exceed the rating.

One question is that I thought the voltage rating of the OC pin is 6 V from the data sheet, so I drive OC pin at 5V.

Is the rating 5 V? Now I see that the table does not have the unit. Thank you.

Mamoru

+1 Sasikala Thangam 4 months ago in reply to Mamoru Sasaki

TI__Expert 6520 points

Hi Mamoru,

OC didn't have recommended max value - but only Absmax value, It is 6V, As you are operating 1V lower than Abs max, that should be good.

Thanks

Sasi

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UCC21710-Q1: Impedance of OC pin