TPS5432: output short circuit when power up

user4030839

Part Number: TPS5432

Hi TI:
I use TPS5432 , there are ten output short circuit in a hundred(10% defect rate) when I repeatedly power up and power off it,test result is low side mosfet short.
There are two power tree ,
Vin=5V adapter ---TPS5432--4V for core board. repeatedly power up and power off for hundreds of times,TPS5432 is ok.
Vin=12V(isolation power supply module)---5V--TPS5432--4V for core board. repeatedly power up and power off for several times, TPS5432 is damged.
On the isolation power supply module output pin ,I can see a 7V above pulse last for several ns.So
I suspect that over input voltage caused its damge.
Can you give some suggestion?
What condition can cause low side mosfet short?
How can the isolation power supply module eddect TPS5432?

over 6 years ago

0 Jason Wang (BSR-MV) over 6 years ago

TI__Genius 9550 points

hi,
please upload schematic for check.
you can try as below :
1. 5v ready, then EN pull high
2. increase Css value

0 user4030839 over 6 years ago in reply to Jason Wang (BSR-MV)

Prodigy 160 points

hi,
my schematic as below.
1.EN pull high meaning add an external divider on EN pin?
2.Css value ,webench suggest 5.6nF ,but i only have 5.1nF,is it ok?

0 Jason Wang (BSR-MV) over 6 years ago in reply to user4030839

TI__Genius 9550 points

hi,
find my feedback:
1.EN pull high meaning add an external divider on EN pin?---------yes
2.Css value ,webench suggest 5.6nF ,but i only have 5.1nF,is it ok?-------Suggest 22nf

0 user4030839 over 6 years ago in reply to Jason Wang (BSR-MV)

Prodigy 160 points

hi，

thanks for your reply.

1.with EN pin divider:R=15K,R=6.2k. now Vin has a voltage drop for 500mv,when no load,tps5432 can power up,when Iout is 500ma,tps5432 output hiccups.why?

2.with Css=330nF,en pin no divider,when power up and power down,tps5432 will still damage.

3.what does the en pin affect and how?

many thanks.

0 Jason Wang (BSR-MV) over 6 years ago in reply to user4030839

TI__Genius 9550 points

Hi,
In your description, "with EN pin divider:R=15K,R=6.2k. now Vin has a voltage drop for 500mv", the Vin voltage drop for 500mV.
500mV drop is the clue of damage. Normall, VIN can't be drop so big.
check:
1. C3 and C4 must be placed close to PIN 2(VIN)
2. Trace width (to VIN pin) should be no less than 40 mil

upload your PCB Layout for check.

0 Anthony Lang over 6 years ago in reply to Jason Wang (BSR-MV)

TI__Expert 4875 points

Hi,

I just have a guess that you may either get into the reverse overcurrent protection during prebiased start up or no boot charge during prebiased start up. Could you please to change another inductor like 4.7uH with higher saturation current? It will tell us whether you get into reverse overcurrent protection.

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TPS5432: output short circuit when power up