TPS40050: TPS4005 abnormal issue

Hello Han,

Would you clarify how you want to adjust the RKFF and RA values? What is your spec over temperature? The voltage variation over temperature is expected due to temperature coefficient of internal reference and external resistors.

-Yang

Do you want to lower UVLO and are not able to acheive the same . Is the device not starting up in cold temperature at required vin(min).
Please go over below appnot for more info on programmble UVLO and its effect on Max duty cycle .

www.ti.com/.../slua310.pdf


Ambreesh

Dear Ambreesh and Yang,
Thanks for your reply. CTM wants to operate it at -40 deg C environment , and currently issue that SMPS can’t turn on.
Check the UVLO point don’t enough to turn on SMPS. So we want to adjust the UVLO from 10V to 9.2V for this issue.
So we adjust the RKFF (from 62K to 55K ohm) and RA (from 430K to 443K ohm) value.
But found the UVLO point still failure and output voltage will serious drop (Feel like that feedback and compensation were also deranged).
Sorry. Could you please help to tell us how to set it for lower UVLO (9.2V) ?

Note: RKFF_62K and RA_430K can normal operate when Vin (10~32V) & ambient (25 deg C)

Thanks.

The TPS40050 is not recommended for new design, as shown in the ti.com product folder: www.ti.com/.../TPS40050

It is replaced by TPS40055, tps40057.

Would you try the TPS40055/7 to see whether it has the same behavior or not?

You may also consider LM25116, LM25117

-Yang

Dear Yang,
Now PWM IC is TPS40057 for 5V/4.8A and already layout PCB , assembly test stage…
So we can’t change to other solution.
Sorry. Whether possible to adjust the lower UVLO (9.2V) of TPS40057 from RKFF & RA value ?
Thanks for your help.


Thanks.