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TPS2660: Is TPS2660 broken when IN-GND voltage is reversed with /SHDN=L?

Kazuya Nakai59
Guru 20100 points
Part Number: TPS2660

 Hi guys,

 One of our customers is considering using TPS2660 because the device is not broken even if VIN-GND voltage becomes a negative (reversed). But the customer has the following questions. Could you please give me your answers for the customer?

Q1. They want to use TPS2660 with /SHDN terminal pulled down by a resistor to GND. The /SHDN terminal is pulled up by push button or a output port of micro controller for TPS2660 activation. If VIN-GND voltage is reversed (becomes negative voltage) when /SHDN terminal pulled down by a resistor to GND, is the device broken or not broken?

Q2. /SHDN threshold voltage at falling edge is 0.76V(typ). What is /SHDN threshold voltage at rising edge? The typical voltage is 1.0V? Does /SHDN have any hysteresis voltage between rising and falling?   

Q3. When I(/SHDN)=0uA, what voltage the /SHDN terminal voltage goes up to? Is it 4V as the maximum? Also what is Avdd voltage in the device block diagram?

Q4. On page 6 in the device datasheet, the following spec is shown.

   LOW IQ SHUTDOWN (SHDN) INPUT

   Parameter                           Test Conditions       Min      Typ      Max      Unit

   V(SHDN) Output voltage   I(SHDN) = 0.1 μA      2          2.7        3.4       V

  I think the test condition, "I(SHDN) = 0.1 μA" is not correct and "I(SHDN) should be -0.1 μA. Is my understanding correct?    

 Your answer would be appreciated.

 Best regards,

 Kazuya Nakai.

 

  • 0
    TI__Genius 16305 points

    Hi Nakai,

    Ans for Q1: Pulling SHDNb pin to GND by a resistor and controlloing with a micro controler is not a problem during reverse input polarity condition. When VIN-GND is -60V, RTN pin of the device will be close to -59V (w.r.t GND) and SHDNb will close to GND. This is not a problem, because SHDNb-RTN has a absolute maximum rating of +60V. But for FLTb (reporting fault status to microcontroller) and IMON (monitoring current), we recommend to add a 150k resistor in series (between device pin and microcontroller) to limit current during reverse VIN condition.

    Ans for Q2: SHDNb has a hysterisis of 20mV typical, but since this is a digital contol pin, we have not specified in the datasheet.

    Ans for Q3: SHDNb operating max is 4V, but internally SHDNb is pulled weekly to 3.15V with 667Kohm week pullup.

    Ans for Q4: Yes, I(SHDNb) of 0.1uA is sinking current, current out of SHDNb pin.

    Let us know if you need further support on this device.

    Regards,

    Kari.

    Regards,

    kari.

  • 0 in reply to Karikalan Selvaraj
    Guru 20100 points
    Hi Kari,

    Thank you very much for your reply.
    Your answers are very helpful for the customer and me.

    Thank your again and best regards,
    Kazuya Nakai.