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BQ76952: wakeup detection from shutdown on TS2 pin

Victor TEXIER
Prodigy 20 points
Part Number: BQ76952

Hi,

I have a problem by using the TS2 pin to wakeup the BQ from shutdown mode. The current necessary to detect a ground for the BQ in nearly 1µA. This could not be a problem but I need to use 3 switches in parallel to wakeup my board.

So I decided to make an OR function by using diodes. The problem is when the board is heating (nearly 40°C), the performances of the components fall down and the diodes are not correctly blocked. Others components like MOS transistors are place behind the diodes and have the same problem.

Another constrain is I need to detect the switches state on a µC supplied by one of the BQ internal LDO set to 3V3. So I do not have any other power source than the battery voltage and the BQ wakeup voltage.

So my questions are :

Do you have any example of multiple parallel ground detection for the TS2 pin ?

Do you know a way to know the state of the TS2 pin when it is used as a wakeup ?

Thank you,

Victor TEXIER

  • +1
    TI__Guru 54715 points

    Hi Victor,

    The BQ76952 TS2 will provide its own internal pull up when the part is shutdown.  This voltage is about 5V as shown in the test conditions for the VWAKEONTS2 in the data sheet section 7.3 Recommended Operating Conditions.   

    We do not have an example of multiple wake inputs for the TS2 pin.  I would expect connecting drains of MOSFETs or collectors of NPN transistors to work well or in combination with Schottky diodes or switch contacts. 

    Again we do not have a reference schematic for such a sense circuit.  A FET input amp or FET gate connected to the TS2 may allow sensing as the input will provide a high impedance to the TS2 pin.