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TPS73HD301 RESET function issue.

Hughie Lu64602
Prodigy 30 points
Other Parts Discussed in Thread: TMS320VC5501

Hi Sir,

I have several issues about TPS73HD301 by our customer. They use this part as voltage regulator and supervisor for TMS320VC5501. But they found the RESET function sustained active when system power on.

1. The output voltage of adjustable regulator is 1.26V, but in terms of the description from datasheet the adjustable output voltage below 1.9V the RESET function become unusable. Therefore, could you help me to confirm TPS73HD301 can work well under Vout1 = 1.26V condition? Or is this application totally can not apply?

2. According to their testing, they found RESET function sustained active when the temperature decrease which cause output capacitor ESR increase, so they change output capacitor from electrolytic type (47uF/10V, ESR = 1.35 Ohm) to ceramic type (47uF/10V, ESR = 20m Ohm), then the RESET was not active. Hence, they want to confirm, is the RESET function error is due to the output capacitor ESR and change to ceramic capacitor will fix this issue? Does this change affect the circuit stability?

3. What is Trip-threshold voltage? Is it the reference voltage for RESET gate drive or has other meaning?  

4. Do you have any reference design for this part?

Best Regards,

Hughie Lu

  • 0
    TI__Expert 8890 points

    Hello Hughie,

    1. Yes, unfortunately the RESET circuit for this part is powered, in part, by the output voltage. Therefore, it is reasonable to assume that the RESET function on the 1.26V regulator will not be usable.  A possible alternative to the TPS73HD301 would be the TPS767D (same basic pinout) which I do not believe has this same output voltage limitation.

    2.  We do not recommend using an output capacitor with such low esr.  The data sheet recommends an output capacitor of 10uF with esr between 0.3 and 1.2 ohms.  The ceramic capacitor has too little esr and the 47uF capacitor has too much esr.  In fact it is generally assumed that the esr should be decreased inversely proportional to an increase in output capacitance.

    3. If the output voltage falls to below the trip voltage then the RESET/ goes low to reset the uprocessor.  And visa versa, when the output voltage rises above the trip voltage then the RESET voltage goes high (after 200ms) to indicate to the uprocessor that the output voltage is good.

    4. We do not have a reference design for this part.

    Regards

    Bill