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TPS63001: randomly enables itself

Helge Bochmann
Prodigy 10 points
Part Number: TPS63001

Hello there,

i designed the circuit seen below and have been following all datasheet recomandations. The purpose of the circuit is to switch on a load connected to the 3.3V output of the TPS63001. When the button2 is press-held once for approximately 2 seconds, the tps63001 starts up. To maintain the state a microcontroller is used to pull the enable pin high even if the button is released. This is working so far.

Unfortunately, i observe some really strange behavior. When the circuit is shut down it randomly enables itself vor a few seconds and shuts down again. I even tested the circuit with only a 10 Ohm resistor connected to the 3.3V output and without the microcontroller. Still the same behavior. Input battery voltage ranges between 2.8 and 4.2 Volts. Current consumtion is bettween 200 and 400 mA. Coil is 2.2uH

I would really appreciate any help, since i am really desperate. I tried with two different chips and both show the same behavior.

Best regards

  • 0
    TI__Mastermind 46905 points

    Hi,

    could you measure the waveform of VIN, EN and VOUT to check what really happen during such observation.

  • 0 in reply to Jasper Li
    Prodigy 10 points

    Unfortunately i only have a 2 channel scope. Every picture shows Ch1 V_out and Ch2 V_en.

    The load is a 10 Ohm resistor. V_en is only connected to the button as depicted in the previous post. No MCU or any other periphals are connected. I use a DC lab power supply with lots of power and current limit is set very high. 

    The button is open in every picture.

    From my understanding the EN_pin should be pulled low by the 10k pull down resistor as soon as the button is released.

  • 0 in reply to Helge Bochmann
    TI__Mastermind 46905 points

    Hi

    from the waveform, the EN pin is pull down to low logic. I think there is leakage current into this pin from somewhere. maybe from the 3V3_EN, or the others circuit. please measure the anode waveform of the two diodes

  • 0 in reply to Jasper Li
    Prodigy 10 points

    Hi, thank you for your help so far. I did as requested. Unfortunately, there is no sign that the EN Pin is pulled high frome elsewhere, than the TPS63001 itself. The anode voltage is lower than the cathode voltage and the chip is turned on the whole time.

    Next thing i will try is to remove as much parts as i can to minimize the sources of failure. How about the Lowpass filter (R201 and C202)? Can i connect VINA and PS_SYNC directly to VIN?

  • 0 in reply to Helge Bochmann
    TI__Mastermind 46905 points

    Hi

    it is OK to remove the RC to find the root cause of the EN pin function.

    please also try to remove the two diode.

  • 0 in reply to Jasper Li
    Prodigy 10 points

    Hi Jasper,

    i desoldered both diodes (D201 and D202). Still the same behavior. I even exchanged the chip and soldered a brand new TPS63001 an still got the same problem. I changed the whole board, as well. The load is still a 10 Ohm resistor. 

    The 3.3V are turned on a couple of seconds after the supply voltage is present. The EN Pin is connected to ground via a 10k pull-down resistor the whole time. The longer the chip rested without any supply voltage the longer it takes for its spontaneous switch on.

  • +1 in reply to Helge Bochmann
    TI__Mastermind 46905 points

    Hi,

    the behavior is really strange. I believe there is leakage current into the EN pin. this may be caused by some solder material. I met some very strange behavior before when using some special solder material, and the board is not cleaned. 

    could you try to clean the board? and maybe change the pull down the resistor to 1K.