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TPS61230 input hysteresis

Rozor
Prodigy 60 points
Other Parts Discussed in Thread: TPS61230

My target is to make 5V / 1000mA max with 3 NiMH batteries. The TPS61230 looks very good to make this function.

I adjust the input hysteresis with Vin_off = 2.51V and Vin_on = 3.63V (for reference in the datasheet it's REN1 = 1000k, REN2 = 487k and REN3 = 348k).

The output is normaly at 850mA, so the NiMH current is big. When the 3 batteries are under 2.5V, the TPS61230 switch off. When the ouput current is #0 when the TPS61230 is off, the volatge of the 3 batteries increase more than 3.70V, so the TPS61230 restart but the NiMH voltage fall quickly and the TPS61230 switch off.

If I increase the Vin_on, I affraid the TPS61230 will never start when the 3 batteries are a bit low.

What is your recommandation about this problem ?

  • 0
    TI__Mastermind 46905 points
    1. have you tried to decrease the Vin_off?
    2. if the 850mA current is pulsating current, adding a bulk capacitor to the input may help.
    3. is it possible to reduce the output current at low BATTERY voltage condition.
  • 0 in reply to Jasper Li
    Prodigy 60 points
    1. I can try, but only at 2.3V because it's the specification in the datasheet.
    2. I can try to add capacitor to the input. Now I have 150µF Tantal like the schematic of the Evaluation board.
    3. How to reduce this current function of input voltage ?

    I'm not sure the TPS61230 will start when the Vin < Vin_on, for the first start at the switch on ?
    Thanks for your help.
  • 0 in reply to Rozor
    TI__Mastermind 46905 points
    "How to reduce this current function of input voltage ?"
    it is a system solution, because the battery can't supply this high energy output . the TPS61230 don't have this function.

    "I'm not sure the TPS61230 will start when the Vin < Vin_on"
    No. because the EN pin is logic low at VIN<VIN_ON.
  • 0 in reply to Jasper Li
    Prodigy 60 points

    Hi Jasper,

    The result of the test with 3xNiMH batteries (blue) and the output of TPS61230 (yellow). Vin_off = 2.3V and Vin_on = 3.21V.

    I will try with Vin_off = 2.3V and Vin_on = 3.52V.

    What is your component reference to do this function, your advice ? Maybe you have a better components, I can change.