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BQ25708: REGN LDO remains on after disconnecting the DC source.

Sergey Taranov
Prodigy 20 points
Part Number: BQ25708

Hi!

The charger starts only from the batteries. The charger is in low power mode, the LDO stays off, the quiescent current is minimal. When an input source plugs in, the charger turns on the LDO, the quiescent current increases accordingly. But when the input source is disconnected, LDO remains on, no matter what I do.
How to turn the charger into lower power mode with minimum quiescent current (LDO off, Iq = ~30uA) when the input source  is disconnected?

Thank you!

  • 0
    TI__Mastermind 25800 points
    Hey Sergey,

    Please disable Low Power mode via the I2C register when you go into battery only mode (input disconnected).


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 20 points

    Hi!

    DISABLE Low Power mode via I2C register to ENABLE Low Power mode?? Are you sure? Unfortunately, this also does not work (Vregn = 6.05V, Iq = ~700 uA).

    The sequence of commands that I use:

    1. Power-Up from battery, the BATFET is not used:

    delay_1sec();

    smbus_write(0x32, 0x8000);                                    /* EN_HIZ = 1 */

    delay1ms(10);

    smbus_write(0x12, 0xA202);                                    /* EN_LDO = 0 */

    delay1ms(10);

    smbus_write(0x30, 0x8210);                                     /* EN_IBAT = 1, AUTO_WAKE_UP = 0 */

    delay1ms(10);

    smbus_write(0x31, 0x2F7);                                       /* EN_ICHG_IDCHG = 1 IBAT pin as charge current*/

    delay1ms(10);

    smbus_write(0x35, 0x2005);                                      /* EN_ADC_VBAT = 1, EN_ADC_ICHG = 1*/

    delay1ms(10);

    2. When DC-source is connected, start charging:

    smbus_write(0x12, 0x2202);

    delay1ms(10);

    smbus_write(0x32, 0);                                               /* EN_HIZ = 0 */

    delay1ms(10);

    smbus_write(0x14, CHARGE_CURRENT);

    delay1ms(10);

    3. Stop charging, when DC-source is disconnected:

    smbus_write(0x32, 0x8000);                                    /* EN_HIZ = 1 */

    delay1ms(10);

    smbus_write(0x14, 0);

    delay1ms(10);

    What should I do next to enable Low Power mode (Vregn = 0, Iq = ~30uA)?

  • 0 in reply to Sergey Taranov
    TI__Mastermind 25800 points
    Hey Sergey,

    You mentioned the BATFET was not used. Can you provide a schematic of your custom board?

    Can you also provide a dump of the I2C registers of the charger (reads) under three conditions:
    1) The initial battery only mode where everything is as expected
    2) When you apply the input voltage adapter and the LDO turns on
    3) When you remove the input adapter and the LDO remains on


    Regards,
    Joel H