TPS22913CEVM-656: Re: TPS22913C

Hey Simon,

Thanks for posting your question here, I have a few questions to better understand your situation. 

What are your below operating parameters?

1. input voltage
2. Input capacitance
3. output resistance (or output current)

When you say that the "off slew rate is only 6.6us" do you mean that the output voltage falls from ~90% to ~10% (tF) in 6.6us?

Could you post a scope shot of off the fall time?

Best,

Nick

Hello Nick,

I've inserted a RTF file so hopefully you can see the circuit diagram where U22 lives.

We have measured a damaged part and the resisstance between VIN and GRD is ~ 150Ohms, whereas on a Good device we measure > 150kOhms, does that help indicate what might have happened ?

TI U22 Issue.rtf

Hey Simon,

Thank you for the detail. 

Inrush seems to be under control.

The peak reverse current should be no more than 733mA and will be stopped within 10us. The fall time of your device is dependent on the load current or the load resistance on the switch. The datasheet is spec'd at a load resistance of 10ohms, but your system may have a different load and therefore a different fall time. 

There is an ESD cell on the input pin of the device, the VIN pin is rated down to -0.3V. If there a voltage spike that goes below -0.3V then the ESD cell could be damaged causing a short, which would be similar to what you are seeing as a substantially lower input-pin resistance. 

Have you/would you be able to probe the SW_Batt rail during a failure?

Best,

Nick

Hello Nick,

Many Thanks, that's very helpful, where does the 733mA come from ?

Regards,

Simon

Hey Simon,

The equation to calculate peak reverse current is:

Vrcp and Ron(vin) can be found in the electrical characteristics table shown below:

Vrcp = 44mV and Ron(4V) =~60mohms

Ircp = 44mV/60mohms = 733mA

if you have any other questions let me know.

Best,

Nick