UC3825A: UC3825A: Vot control mode Cloesd loop. No PWM Out

Lei wang

Part Number: UC3825A
Other Parts Discussed in Thread: UC3825

Hi Sir:

I use the Device UC3825，In the open Loop.It is OK. But In Closed Loop. The Pin Limt is connect to GND. And I test the 5.V-Vref,RAMP is OK the Clk the 40%.and The secondary side feedback use an optical coupling. But the PWM like be Latched,ref the datasheet(UVLO, SOFT-START AND FAULT MANAGEMENT)

and I find the soft-start Cap if less.It normally work. So Why?

over 4 years ago

0 Teng Feng over 4 years ago

TI__Genius 13660 points

Hi Lei, I will get back to you soon. ——Teng

0 Teng Feng over 4 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi Lei,

Yes it looks PWM output is latched.

May you share your test circuit schematic?

Besides the waveform of E/A pin (pin 3), ILIM pin (pin 9) and SS pin (pin 8)?

Regards,

Teng

0 Teng Feng over 4 years ago in reply to Teng Feng

TI__Genius 13660 points

Hi Lei, I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out) – thanks, Teng

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UC3825A: UC3825A: Vot control mode Cloesd loop. No PWM Out