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TPS7B63-Q1: TPS7B6350-Q1 Line regulation question

CHO SR
Genius 3415 points
Part Number: TPS7B63-Q1

Hi,

The customer is applying it to the car temperature control.

If the battery voltage has a rapid drop from 12V to 4V, Vin is less than Vout, so the voltage of Vout decreases after the capacitor attached to Vin is discharged.

It's an expanded situation similar to the above. Yellow (Battery Voltage) / Red (Vout Voltage)

During the course of discharging, a spike is occurring in the regulator's Vout when the battery voltage is normalized again.

(Large than the line regulation value of the datasheet)

As a result of applying various LDO products, this phenomenon occurs in all manufacturers.

Please provide data or explanation to explain to the customer what mechanism this phenomenon is due to in LDO & that there is no problem if the duration of the spike is less than a few time.

Schematic : 5V/50mA

  • 0
    TI__Guru 50025 points

    Hi Cho,

    It is common for LDOs to overshoot when exiting dropout. The reason for this is that when in dropout, the error amp is driving the pass device's gate all the way to its rail so that the channel is fully open, and then when the input rises back up and brings the device out of dropout, the error amp takes a finite amount of time to bring the pass device's gate voltage away from its rail. During this time, the channel is still open and allows current to flow to the output, and the result is that extra charge ends up on the output cap. There is not a good way to prevent this if a dropout condition is expected, although the magnitude of overshoot will be less if the input is ramped back up slowly, which may not be possible to control in a battery application. 

    Regards,

    Nick