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BQ24616: TTC pin Failure in Charger IC.

Rajesh Kaliyaperumal
Intellectual 930 points
Part Number: BQ24616

Hello Everyone,

In order to disable the Fast charge timer , we have connected the TTC pin of charger IC to Vref  using a Zero Ohms resistor( 3.3 Regulator Output from Charger IC). While it is being tested , we have faced that the Reference Voltage from charger IC is 2.8 Volts Instead of 3.3 Volts.

After debugging we have found that TTC pin is causing the Reference of the charger IC to be lower than 3.3 volts i.e 2.8 Volts.

Since Vref is changed our Voltage and current setting to charger IC have varied. 

Could you tell us what is the potential root cause for the TTC pin failure ?? Does it require any Pull Up resistor between TTC and VREF to rectify the failure??

Appreciate Your reply at the earliest.

Ragards ,

Rajesh

  • 0
    TI__Intellectual 1980 points

    Hello,

    Use a 0.1uF cap between TTC and GND. A nd connect TTC to VREF.

    Regards

  • 0 in reply to Kerry Song
    Intellectual 930 points

    Hi Kerrey,

    After replacing the charger IC with new one in our board , Vref is now correct  (i.e showing 3.3 volts) but the board is charging at 920 mA instead of 750mA which is set fast charge current using Viset1.  

    I have measured the Viset 1 voltage and found to be correct for 750mA of charging  . Also checked the  Current sense resistor Placed between SRP and SRN if its value is changed but that is also found to be correct.

    What other reason could cause this Increased charging current to 920 mA instead of 750 mA ??

    Thanks in Advance.

    Regards,

    Rajesh 

  • 0 in reply to Rajesh Kaliyaperumal
    TI__Intellectual 1980 points

    Hello,

    What's your voltage of ISET1 pin, please confirm that the voltage test point is near your IC's ISET1 pin.

    What's your resistance between SRN and SRP pin, please confirm that test the resistance near your IC's pin, other than near the resistor.

    Also, could you tell me your charge current test condition and test equipment.

    Regards

  • 0 in reply to Kerry Song
    Intellectual 930 points

    Hi Kerry,

    Voltage on Iset 1 is 0.749 Volts and which is measured very near to charger IC.

    Resistance between SRN and SRP pin is 0.05Ohms and resistance also placed close to charger IC.

    Charge current test condition is 750mA charge current and 150mA Precharge/termination current @ 25 deg Celcius.

    19 volts will be supplied from an RPS (Regulated Power Supply) for charger IC.

    Hope you have got all the related Information. Looking forward for your reply.

    Thanks and Regards

    Rajesh

  • 0 in reply to Rajesh Kaliyaperumal
    TI__Intellectual 1980 points
    Hello,

    I think that your result is normal. charge current = VISET1/R/20, the 750mA current is OK.

    Regards