TPS5430: schematic check --negative output

Sherry Liang

Part Number: TPS5430
Other Parts Discussed in Thread: LM337

Dear team,

When configure TPS5340 as a buck boost, the TPS5340 can output negative value. TPS5340's output is LM337's input. When disconnecting these two device, they are working normally, but once connecting these two device(LM337 has no load at this time), TPS5340 will be damaged. Is there any wrong with the TPS5340's design? Could you please help analyze this question? TPS5340's input is smaller than 30V.

Thanks & Best Regards,

Sherry

over 3 years ago

0 Marshall_Beck over 3 years ago

TI__Mastermind 29670 points

Hello Sherry,

Damage for device often occurs due to ABSMAX violation.

How is connection being made?

IS this between two EVMs via wires, jumpers of some sort?

Long wires and the inductance associated with them could create some ring.

Oscilloscope plots capturing the failure could also be beneficial. Ensure resolution is sufficient.

0 Sherry Liang over 3 years ago in reply to Marshall_Beck

TI__Genius 10255 points

Hi Marshall,

We found that VIN and PH pins are short to ground. It seems that ABSMAX violation should be the reason. But we still have one question is that the fault occurs only when connecting LDO. At the first test, 5430 has no load, and it works normal, but once 5430's output connected with the LDO, the device is damaged quickly. Why 5430 works normally with no load even though ABSMAX violation existing? Could you please help analyze this?

This is the customer's schematic, not the EVM board.

Thanks & Best Regards,

Sherry

0 Marshall_Beck over 3 years ago in reply to Sherry Liang

TI__Mastermind 29670 points

Hello Sherry,

VIN to phase short signifies there was electrical stress on high-side FET.

It appears that potential difference between IC ground and VIN is 36V - (-18V) = 54V.

Absolute maximum rating for VIN is 40V.

Below are 60V devices that can support application. Please ensure sufficient margin on absmax by having appropriate input protection.

In addition, please let me know if below device meet system criteria. In inverting buck boost application, average inductor current does not equal the load current.

This application note will be useful in your design.

https://www.ti.com/lit/an/snva856a/snva856a.pdf?ts=1592842866606&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/product/LMR36015

https://www.ti.com/product/LM76002

https://www.ti.com/product/LM76003

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TPS5430: schematic check --negative output