TL431 issue

Patrick Chen

Other Parts Discussed in Thread: TL431

Hello,

Below is customer schematics. PD132 is 36V zener. PD37 is Phototransistor. PU26 is TL431.

if PSU_54V > 48V, TL431 reference voltage is over 2.5V then PD37 1/2 pin turn on to indicate PG_54V_N is low and power source ready. But per waveform, the voltage of TL431 CATHODE is only 2V. Is it correct for the 2V by TL431? Has any concern for it? Thank you .

Patrick

over 9 years ago

0 ShreyasRao over 9 years ago

TI__Guru 62170 points

Hi Patrick ,

I have moved your post to the appropriate forum for support .

0 Patrick Chen over 9 years ago in reply to ShreyasRao

Mastermind 8875 points

Hello,

Has any update and suggestion for above issue? Thank you.

Patrick

0 Michael J Schultis over 9 years ago in reply to Patrick Chen

TI__Mastermind 24975 points

Hello Patrick,

When using the TL431 in this type of mode (comparator mode), as described in Section 10.2.1 of the datasheet, we do expect that the cathode of the TL431 will drop to about 2V. There is no concern for the device in this application responding in this manner.

Please refer to the following E2E post for additional details on this mode of operation:
e2e.ti.com/.../1689982

Best,
Michael

Power management

Power management forum

TL431 issue