TPS922054: TPS922054DRRR

I would like to add the fault pin is pulled up to 3V3 .  

Dear Nikhilraj,

Thanks for reaching out! Pls kindly let me check and get back to you during these days. Thank you!

BRs

Lucia

Hi Lucia , 

Yes the board is for PWM dimming . 

The board  started working after we swapped the UVP resistors(R16 and R17)  . But now facing another issues , a few boards stops working after a while and not at all responding the the PWM . In fact the LEDs are ON even if the PWM  signal is not applied . Is this indicate Chip is damaged ?  Fault signal is high .   

Any method to debug it ?   

Vin  = 12V   , VCC = 4.8v (internally generated) 

on further investigation it found ,diode D2  was open in those boards , What is the possibility of chip damage here ?

Dear Nikhilraj,

I'll check your question and get back to you soon. Thank you!

BRs

Lucia

Dear Nikhilraj,

Without PWM signal, there should not be switching pulses. 

Not sure if you have chance to try to  change R11 from 9k to 38k and change Rtemp (R10) from 100k to 10k.

And for UVP resistor design, you can refer to [FAQ] How to design the UVP resistor divider for TPS922055 / TPS922054 / TPS922053 / TPS922052? What is the LED string forward voltage?

Thank you!

BRs

Lucia

Hi Lucia , 

The Schottky  diode in the SW pin was not properly assembled and it was like an open circuit . Do you suspect this  lead to the permanent IC damage ? 

We were not able to change the R11 and R10 as you suggested  , this can be an issue? 

LED forward voltage is 9V.  ( 3 LEDs in series) .

Now the condition is  even when no PWM signal , LED is on . When PWM  is applied there is a only a slight change in the intensity ( initially it was working properly) .    Fault pin is high , VCC (pin2)  is 4.8V , So is there a chance the internal mosfet  (SW pin )  is damaged .   This issue is with 3 boards .

Dear Nikhilraj,

Thanks for your feedback. Pls allow me some time and I'll give you feedback tomorrow. Thank you!

BRs

Lucia

Hi Nikhilraj,

Thanks for your feedback. We don't suggest to leave SW pin floating  (Diode open circuit). Could you pls assemble the rectifier diode and try again? Thank you!

BRs

Lucia