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TPS60401: Dimming output

Alexander Alioshyn
Prodigy 170 points
Part Number: TPS60401

Dear support team,

There is a figure 32 at the datasheet of TPS60401. It shows that shutdown control can be made with a push-pull inverting buffer. I have some quite small load: 200uA typical with 4mA as max load which needs a negative supply of something around -3V. I don't need any regulation but I want to be able to dim output voltage from -Vin down to 0 volts. Is it possible just to apply a PWM (500Hz is enough) to IN pin of these charge pump and get some PWM at its output?

  • 0
    Guru 316510 points

    The TPS60401 can quickly discharge the output capacitor (Q5 in the functional block diagram). But during startup, the output capacitor must be charged, and this requires switching for a certain time (and more current; see figure 5). To decrease startup time (and increase ripple), increase the flying capacitor and/or decrease the output capacitor.

    I guess PWM is possible to a certain degree, but you have to actually test it to find out whether it is good enough for your application.