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BQ24773EVM-540: Some Question about BQ24773EVM

Nicky Lim
Genius 3195 points
Part Number: BQ24773EVM-540

Hello,

There are some questions during BQ24773EVM test as below.

-. Do I have to use TPS3898ADRY(U2) for BATPRES or can remove it to use internal comparator?

    -.  Set S1 switch as 1 & 2 close, 3 & 4 open to use internal comparator, BATPRES LED is ON without Battery.

    -. Is there anything to set to use internal comparator? 

-. According to EVM BOM, all resistors' tolerance is 1%. 

    -. Can I use 5% resistors instead of 1%?

-. During charging test, D2(BAT54C-7-F) goes to fail.  Could you let me know the maximum current of D2 when battery charging? 

    -.  Let me know why this Diode goes to fail?

-. If I don't want to use Vsys Out, how can I treat SRN/SRP pin? 

    -. All components for Vsys can be removed?

-. Could you let me explain the purpose of Q1A & Q1B on EVM?

Regards,

Nicky

  • 0
    TI__Guru 56650 points

    1. You can remove U2 and use the internal comparator only according to your circuit function.

    2. Most resistor can use 5%, but for current sensing resistor. Please keep it 1% or better.

    3. When D2 is damaged, does VCC series resistor R16 get damage? If not, I would think D2 soldering issue. If R16 to Vbat side of D2 is short, it can get damage.

    4. Most output capacitors on Vsys. You can remove the C4, C5 electrolytic capacitors.

    5. If input short, Q1B can block the battery discharge current to input terminal. If input OVP or sys short, Q1A can disconnect the system from the input.

  • 0 in reply to Wang5577
    Genius 3195 points
    Hi Wang,

    Thank you for your kind answer.

    I have one more question about using internal comparator.
    If wants to use 2-Cell battery, do I need to change the resistor value of R32//R39?

    Regards,
    Nicky
  • 0 in reply to Nicky Lim
    TI__Guru 56650 points
    It is a resistor divider: Rtop=R32=140k; Rbottom=R39=100k. You should be able to calculate the divider output voltage is 1/2.4*Vbat and the internal comparator threshold is 1.2V or 2.3V <default at POR>.
    "do I need to change the resistor value of R32//R39?" I think you may need to adjust the resistor divider value. But, first, please check why do you want to monitor the VBAT?
  • 0 in reply to Wang5577
    Genius 3195 points
    Hi Wang,

    One more question,

    4. Most output capacitors on Vsys. You can remove the C4, C5 electrolytic capacitors.
    ==> Can I remove C7~C10 capacitors on Vsys?
    Please let me get your confirmation.

    Regards,
    Nicky
  • 0 in reply to Nicky Lim
    TI__Guru 56650 points
    C4, C5 are added to simulate the system load input capacitance. They can be removed.
    Don't recommend remove C7~C10 capacitors on Vsys. The EVM setup is fully evaluated. If you want to change to other value, please do enough evaluation to make sure the new value working.