TPS55340: TPS55340 question for flyback topology

Sulyn ZHANG

Part Number: TPS55340

Hi Team,

We penetrate our TPS55340 in our customer to build flyback topology. We got several questions and want to double check with you:

1. From our datasheet, the source and sink current on COMP pin is about 42uA:

Not sure if this source current can meet flyback's application which will use a opto which may sink/source current?

As for the opto device:

When operating under higher temp, the Idark will increase from nA to uA, so will this influence the close loop of the fly-back since TPS55340's Isource is only 42uA?

Customer have concern for this and need expert kindly help clarify.

Best regards,

Sulyn

over 5 years ago

0 Helen chen over 5 years ago

TI__Mastermind 40080 points

Dear Sir，

You need to add a pull up resistor to the opto-coupler's transistor.

0 Sulyn ZHANG over 5 years ago in reply to Helen chen

TI__Expert 8700 points

Hi Sir,

Thanks for the support! For the pull up resistor, do you mean the secondary side(Yes this resistor is need)? But the question is how about the COMP pin of TPS55340? Do you mean still need pull resistor here? Pls help clarify, thanks.

BTW, below is a flyback reference schematic with our TPS55340, only one pull down resistor on the COMP pin as showed: