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TPS27081A can not turn off

Fei Yan1
Intellectual 575 points
Other Parts Discussed in Thread: TPS27081A

Hi,

I have a same problem with 

http://e2e.ti.com/support/power_management/power_interface/f/204/p/262224/1185310.aspx#1185310

If the ON/OFF pin is low level, the output voltage is about 1.7V. This chip will provide power for a bluetooth module and a camera module. If without any load, the output voltage will be 0.8V.

Also I tried the TPS2702L. I get a same result.

Can you give me some suggestion to fix this problem?

Thank you

Fei

  • 0
    TI__Expert 5275 points

    Hi Fei,

     

    Just to confirm with ON/OFF = 0V.  The output voltage is 1.7V when loaded and 0.8V when unloaded? 

    What is the load current and input voltage?

     

    Regards,

    Adam Hoover

    DLS Applications

  • 0 in reply to Adam Hoover
    Intellectual 575 points

    Hi,

    Thank you for your response.

    Yes, I can confirm that the ON/OFF pin is 0V. Also the output voltage is 1.7V when loaded and 0.8V when unloaded.

    When the ON/OFF pin is 3.3V, the output voltage is 3.3V. It is normal.

    The load current will be not more than 500ma and the input voltage is 3.3V.

    When TPS27081A is used, R1 = 10K, R2 = 1K and C1 = 0.18uF.

    Thank you 

    Fei

  • 0 in reply to Fei Yan1
    TI__Guru*** 140126 points

    Fei,

    Both TPS27081 and TPS27082 are high side load switch but don't have an output discharge when turned off.

    First verify the R1C1 pin is same voltage as VIN when switch is off.
    While off, short output to ground to discharge output cap. Then monitor output to see if it goes back up.

  • 0 in reply to Ron Michallick
    Intellectual 575 points

    Hi, Ron,

    I verified that the R1C1 pin and the VIN pin are 3.3V.

    While off, ON/OFF pin is 0V, R1C1 pin and VIN pin are 3.3V, R2 pin is 0V, OUT pin is about 2.0V(vary between 1.9 to 2.0).

    When I short the OUT pin and ground, I can see a small fireball because of this short circuit. After this, the OUT pin is still 2.0V.

    Thank you

    Fei

  • 0 in reply to Fei Yan1
    TI__Guru*** 140126 points

    Fei,

    I'll assume the fireball was just the output cap discharging suddenly.

    Let's trying something more subtle. Can you add a resistor from output to ground (between 1k to 100k) and measure Vout again. I don't know much about your application load so the resistor will help gauge how much off current is flowing.

    Ioff will be about Vout/Rload.