TPS548A20: Rtrip resistor design inquiry

JH Shin

Part Number: TPS548A20

Hello,

My customer had an issue as the link below on the TPS548A20 they designed.

- https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1230796/tps548a20-device-failure-history/4651108

Recently they found the below recommendation in the datasheet for the Rtrip resistor.

The TPS548A20 they designed was out of this range and used 68.1K (R2093).

Q1) Why is the resistance range limited?

Q2) What symptoms can occur when using values outside this range?

Thank you.

over 1 year ago

0 Joseph Conrad over 1 year ago

TI__Expert 7860 points

Hello JH,

Let me look into this and I will reply by end of today.

Thanks,

Joseph

0 Joseph Conrad over 1 year ago in reply to Joseph Conrad

TI__Expert 7860 points

Hello JH,

JH Shin said:
Q1) Why is the resistance range limited?

These are recommended ranges intended to protect the device. RTRIP sets the overcurrent protection limit for the device.

I ran the calculations per the datasheet and for the 3.3Vout device, I_OCP =~ 20.5A.

R_TRIP_calc.xlsx

JH Shin said:
Q2) What symptoms can occur when using values outside this range?

If the Rtrip is set above the range the device will eventually be clamped to the maximum around 65-70k (per this thread (+) TPS548A20: Rtrip setting question - Power management forum - Power management - TI E2E support forums)

With Rtrip = 68.1k, this would set it around the maximum OCP limit.

Let me know if this answers your question.

Thanks,

Joseph

0 JH Shin over 1 year ago in reply to Joseph Conrad

Mastermind 8915 points

Hi Joseph,

Thanks for the reply.

As a result, is it acceptable to use a resistance value that exceeds the customer's Rtip recommended range? Or should they change it within the recommended range?

Regards,

+1 Joseph Conrad over 1 year ago in reply to JH Shin

TI__Expert 7860 points

Hi JH,

If the Rtrip exceeds the recommended range the device is supposed to clamp to the max OCP setting.

Just to be safe, I suggest setting it between 49k-65k. This will put it close to the maximum I_OCP but not over.

Since the I_out_max for the 3.3V rail is only 5.8A (and no transients higher than this?) a 15A OCP should have plenty of margin.

Thanks,

Joseph

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TPS548A20: Rtrip resistor design inquiry