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TPS544B25: Ton_max_fault shut down

Sen Velmurugan
Prodigy 10 points
Part Number: TPS544B25

WE have been using the TPS544B25 for various out put voltages from 0.8/1.1/1.2/1.5/1.8/2.5/3.3/5.0V all with Rt=20.1K which is 1Mhz switching Freq. The tisp file to program the device was provided by the FAE. The same tisp file has been used for many board design with same circuit. Later we learnt that 100nS min PWM pulse width, then all the low vottage REGs need to run at low freq to meet the spec.

However, when the power supply was brought up using the same tisp file as it is agnostic to freq of operation, some of the REGs shutting down when powered up wtih Ton_max fault.

The only way to make the REG to work is by giving wide UV and OV protection setting and even Ton Delay increase. All these nothing to do with this fault either.

We wonder if there is any other setting in tisp file which we can tweak ?

Thanks

Sen

  • 0
    TI__Genius 9506 points

    Hi Sen,

    Yes, to run at 1MHz switching frequency at 12V input, the output needs to be higher than 1.2V. If you want to run all rails at the same switching frequency, the switching frequency needs to be 500kHz or less.

    First, I recommend disabling the TON_MAX_FAULT timer by setting TON_MAX_FAULT_LIMIT = 0 and checking if the output powers up without UV or OV fault. I'm guessing with your current TON_MAX_FAULT setting, the output takes a long time to ramp up, therefore, triggering the UV fault when the timer expires.

    Another thing you can do is change the TON_MAX_FAULT_RESPONSE to ignore the fault and zero retry setting.