UCC28180: UCC28180 Brown out issue

Hi John,

Sorry, customer hope we don't post sehematic on web and create new post.
Currently we test by open loop monitor gate PWM and if became -0.7V is there cause power limit?

This external circuit should have some hysteresis added around the LM8364 so that there is a sharp brownout point
->Currently Reset IC output low then gate of UCC28180 still output 4 cycle PWM.

Regards,
Kuo

hyster.pdf

Hi Kuo,

Please take a look how hysteresis was implemented with the LM8364 on the attached document.

This can be used to pull VSENSE low on the UCC28180 and shut off the PWM.

Regards

John

Hi John,

1. LM8364 & LM8365 is same device. just thorehold voltage different. Looks Reset function OK. But UCC28180 not shut down PWM when OLP!?
2. Removing one of the reverse polarity diodes on the ISENSE pin. issus still have.
3. Currently fail PWM cause MOSFET damage, so we test open loop(remove MOSFET)
4. Verification VSEN direct short to GND, trigger OLP will not shut down PWM.

CH1 Trace Reset of LM8365
CH2 PWM of UCC28180
CH3 VACIN of LM8365

CH1 Trace Reset of LM8365
CH2 PWM of UCC28180
CH3 VACIN of LM8365
CH4 VSEN of UCC28180

Hi John,

If this behavior is UCC28180 have.
Could you help comment for it? or we just increase power component rating such as MOSFET UIS?
Brownout Implement by OVP?

Regards,
Duke

Hi Kuo,

I also recommended adding hysteresis to the brownout detection circuit as in the attachment I posted.

Did you try this?

Regards

John

Hello Duke,

I am attaching a circuit that shows how to add brownout to the UCC28180.

This has been tested and as far as I know has no problems.

Regards

John

brownout.pdf

Hello Duke,

It is impossible to know what is going on without the schematic.
What is the RSET signal  and why is it slowly decreasing?

Regards

John