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Original question:

BQ24074: CHG pin promble

BQ24074: Battery won't charge and PGOOD and CHG LEDs on when no battery is connected.

Bill William
Prodigy 10 points
Part Number: BQ24074

Greetings,

I have built the circuit in the schematic below and have problems with battery charging. None of the external status or EN pins are connected just for bench top testing.

When I have an external source and no battery connected both the PGOOD and CHG LEDs light up. When I connect a battery the CHG LED turns off but I have no current draw from my external source and no battery charging.

With no external source I can run the circuit off battery fine until it is flat (~3.2v). It just will not charge.

Let me know if you need more information or specific readings.

Cheers,

Bill

  • 0
    TI__Mastermind 22840 points

    Hi Bill, 

    Thank you for reaching out via E2E. Please see my comments below. 

    Firstly, it is not necessarily related to the charging issue you are seeing, but reviewing the schematic I noticed your ILIM resistor is out of the recommended range. ILIM resistor is recommended to be in range of 1100 ohms to 8kohms. 

    Additionally your schematic does not show any output capacitor at BAT pin or OUT pin. Please help to confirm if you have output capacitors at these pins. Both these pins require a capacitor be placed close to the IC. The recommended range is stated in the Pin Functions table in the datasheet (table 7-1 on page 8).

    Bill William said:
    None of the external status or EN pins are connected just for bench top testing.

    Can you help to clarify your test setup. Is my understanding correct that both EN pins are left floating? For your testing please ensure EN1/2 pins are either driven high or low. To ensure the highest input current limit set EN1 = 0 (GND) and EN2 = 1. Additionally have you confirmed CE pin is connected to GND when attempting to charge? Is there any load connected at Out pin?

    Regards,

    Garrett 

  • 0
    Prodigy 10 points

    Thanks for the reply Garrett!

    To clarify some details about my original post and test set up.

    1. EN1 is to GND and EN2 is high in my set up (as per schematic)

    2. CE is connected to ground during charging through the 10k pull down resistor

    3. I've placed capacitors as per the spec sheet at the Out and Bat pins and see no change.

    I do have a load connected to the Out pin. This is how I determined that the battery is not charging as the current drawn from my power supply connected to In does not change if I connect a battery which needs to be charged.

    Cheers,

    Bill

  • 0 in reply to Bill William
    TI__Mastermind 22840 points

    Hi Bill, 

    Thank you for your response and clarifying your test setup. I have a couple additional questions. 

    1. What is the current draw from your power supply due to the load at Out pin? 

    2. Is the not charging behavior the same if you have battery connected to BQ24074 IC before connecting your input power supply? 

    I also recommend you check if the device is able to charge with CE connected directly to GND and without the 10K resistor along the path. 

    Best Regards,

    Garrett