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TPS2066: One more question about Enable Pins

Part Number: TPS2066

Folks,

coming back to the TPS2066 Enable Pins:

We want to use the device as a simple Undervoltage Protection Switch. Our external supply is a One Cell LiIon battery, which works properly in a range of 3.0 to 4.2 Volts. This source is connected to pin 2 (Input) and parallel to pin 3 (EN1). Our idea is that the battery voltage will be passed to the output OUT1 as long as the battery voltage is higher than 2.7 volts. 

We tested three different TPS2066 devices but all show the same behavior: If the battery voltage falls below 3.6 volts, the switch turns off. After the battery voltage will be increased above 3.8 volts, the switch will turn on again.

The output load is very small, approx. 20 mA, and connected capacitors are only 10 uF. The output load is mainly a 3.3V LDO and a microcontroller behind it, but even if we put the micro into permanent reset state (so only DC current will appear), the behavior is still the same...

What are we doing wrong?

Thanks and best regards,

Ulf

  • Hi sir,

    The operation voltage range is from 2.7V to 5.5V of tps2066.

    1. And the voltage is the pin voltage instead of battery voltage.

    2. make sure EN pin voltage is above 2V.

    3. If still not work, use the power supply to power the IC to have a try.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • Hi Zhang,

    thanks for your answer, but unfortunately it does not help...

    The expected operating voltage of our circuit is from 3.0V to 4.2V - so it should fit to the TPS2066, shouldn't it?

    We want the battery to be disconnected, if it drops below 2.7V.

    We connected the EN pin directly to VIN, so this pin will be above 2V at any time.

    Of course we tested it not only with a battery, but also with a power supply, which has enough power and can be set digitally in 0.1V steps. 

    The behavior (switch off already below 3.6V, then switch on above 3.8V) of the TPS2066 can be reproduced also on three different boards, so something must go wrong there.

    We need the TPS2066 switch off at approx. 2.7V, not 3.6V.

    Thanks and regards,

    Ulf

  • Hi Sir,

    Please check Page4 of the datasheet.

    The UVLO voltage is (2V, 2.5V), which means that need to drop below 2V to turn off the switch.

    As for 3.6V to switch off the IC, I need to have a test on EVM board.

    I have ordered the IC on Ti store. Will reply to you at the end of this week if possible.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • Hi Zhang,

    yes, the undervoltage detection range is ok for us from 2V to 2.5V. This is only an emergency function in case the battery does not work as expected.

    The switch-off should happen below those range but not at higher voltages like 3.6V as we observed.

    We are looking forward to read about your tests with the EVM board.

    Thanks, regards,

    Ulf

  • Hi Sir,

    For TI's policy, it must be replied in 24hrs.

    I will first close this thread first and will give you the result before Wednesday of this week.

    Thanks.

  • Thanks, we are lookingh forward to hear about your experiences.

  • Hi Ulf,

    I have a test on EVM board.

    With 20mA load, tps2066 turns on at 2.3V and turn off at 2.2V.

    Maybe you can separate the IC and remove other circuits and power on.

    If still no improvement, please send me the schematic for a check.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • Hi Zhang,

    strange... we separated any load from the output, but the situation stays exactly the same. The TPS2066 switches off at 3.5V and switches on at 3.7V.

    So this is the part of the circuit:

    You see: BAT+ is where our external Power Supply is connected. The line "OSC-Power" remains low because the controller is not activating it. IN and EN1 are connected together directly at the IC pins. OUT1 is where we measure the output voltage. Now everything is disconnected from OUT1.

    OUT2 is off, 0V.

    If IN is below 3.6V, OUT1 goes to 0V. If we then increase IN-voltage above 3.8V, OUT1 shows 3.8V again. This can be repeated.

    This behavior is same on three boards. All have the same TPS2066 which we bought in one lot at Mouser.

    Any idea?

    Thanks and regards,

    Ulf

     

  • Hi Ulf,

    I think you use the wrong version of TPS2066C.

    You should choose tps2066 version.

    Please double check.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • Hi Zhang,

    small difference - big change!

    You are perfectly right. We looked into the data sheets and also bought some TPS2066 - now they work fine.

    Thank you for your assistance!

    Best regards

    Ulf