UCC28064A: Maximum current rating for internal clamps at ZCD pins

JGE

Part Number: UCC28064A
Other Parts Discussed in Thread: UCC28063

Hello,

I have a doubt probably you could clarify.

Datasheet for UCC28064A shows a typical application using a value of 3mA as maximum current rating for internal clamps. I cannot see clearly where this value comes form. The only information I can find related with it is on abosolute maximum ratings table. It shows 5mA as maximum continuous current. However, in recommended operating conditions there is not information about maximum current but about the resistor to put in serie with ZCD pins. I cannot see a direct relation between this resistor and the maximum current unless that the maximum voltage is specified.
Could you please put some light about it?

Thanks

Jesús

over 2 years ago

0 David Huang33 over 2 years ago

TI__Genius 9140 points

hello Jesus,

the maximum voltage on the aux-winding is Voltage of PFC output divide by turn ratio of PFC inductor.

20kohm-80kohm between ZCD* and aux-winding is just to limit the current below 3mA that is the recommend value.

0 JGE over 2 years ago in reply to David Huang33

Prodigy 60 points

Hi David,

Thanks for your reply.

I knew how the resistors work to limit the maximum current through ZCD. My question was, however, where the datasheet for this part specify something like a recomended maximum current of 3mA. Because the only place where 3mA appears is when the calculations are done for a typical application.

Jesus

0 David Huang33 over 2 years ago in reply to JGE

TI__Genius 9140 points

Hello Jesus,

UCC28064A is developed based on UCC28063, I check the datasheet of UCC28063, for the pin description, the datasheet highlight the 3mA here.

I believe when create the UCC28064A datasheet, the system team did not recognize this.

sorry to confuse you.

0 JGE over 2 years ago in reply to David Huang33

Prodigy 60 points

Hi David,

Now everything is clear.

Thanks

Jesús

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UCC28064A: Maximum current rating for internal clamps at ZCD pins