TPS56637: Chip damaged when plug-in 24V as input, the Vin and GND of chip shorted.

Cun Lee

Intellectual 310 points

Part Number: TPS56637

Hi TI

I used TPS56637 in my design, and I found some of them were burn out sometimes. The details as below:

1. the schematic

the sys_power is 24V. the function is output 5V, 9V, 15V.... when drive different N-mos.

2. the layout, picture shows the top layer, the bottom layer is GND copper.

3. I make about 10 boards, and when I first power on those boards, the function is ok.

after I power cycle some times, I found some of the TPS56637 were burned.

some of failed chips are short between VIN and GND. others even worse, the PCB pad also be burned.

currently, the chip I used is still the pre-RTM device, so I want to know

a. if this failure is related with my design or the version of this chip?

b. How can I improve the performance of this chip?

c. the application is to drive the type C power from 5V to 20V (I know TPS56637 only can output 16V max, so in this schematic the max voltage is 15V), is there any other power chip can have better performance than TPS56637?

Thanks

Roy

over 5 years ago

0 Yuchang Zhang over 5 years ago

TI__Mastermind 18510 points

Hi Roy,

1, Firstly for layout, input cap placement and Ground plane need to optimized. this may cause Vin instable.

2, After power up, How Vout change? actually I would like you to confirm which Vout cause the POWER ON/OFF damage. you can fix the Vout one by one and then check this....and also please probe some waveforms for Vin/Vsw and Vout when you confirm which Vout cause this.

Yuchang

0 Cun Lee over 5 years ago in reply to Yuchang Zhang

Intellectual 310 points

Hi Yuchang

thanks for your reply.

1. could you detail the optimize for input cap placement and Ground plane?

2. in my latest test, I remove the R1015, and connect a MCU gpio to EN pin with 3.3V level. So that, I can first disable the chip and use different FB resistor by those nmos.

3. mostly, I test with 15V output. and the failure usually happened when sys_power is power on. (in this case, the TPS56637 is disabled)

last, could you advise a power chip which can fully meet usb type c PD requirement? max power is 20V 5A with input power is 24V?

thanks

0 Yuchang Zhang over 5 years ago in reply to Cun Lee

TI__Mastermind 18510 points

Hi Roy,

you can refer to tps56637 user guide finger1 placement.

http://www.ti.com/lit/ug/slvube3/slvube3.pdf

For item3, do you mean the EN of 56637 is low, the IC damage happen when you power on 24V? if so, it doesn't make sense because it is 28V part.

Can you catch Vin waveform at Vin pin and IC PGND for review?

From my product line, there is no proper device for your application, I suggest you can post another question with "Type-C/PD power choose...."

0 Cun Lee over 5 years ago in reply to Yuchang Zhang

Intellectual 310 points

Hi Yuchang

1. I read the UG, and there is difference between my layout and reference layout which I can optimized.

But I still want to know, if there is any document that can help me further understand why the layout like reference sample can help to improve the performance, OR let me learn more power theory so that I can have good layout even use other chips later?

2. for the TPS56637, is there any schedule for the production release?

Seems it is stay at preview stats for a very long time.