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TPS65720: failed to insert the device to shutdown mode when HOLD_DCDC1 pulled LOW

kobi kiviti
Prodigy 30 points
Part Number: TPS65720

Hi,

we are using TPS657201YFFR as PMIC for wearable device.

i failed to put the PMIC into shutdown mode by lowering HOLD_DCDC1 from HIGH to LOW state after successful power up (powered from battery, PB_IN pulled LOW for ~1 sec).

HOLD_DCDC1 has 100K pull-up resistor to DC2DC output and i saw in the oscilloscope that the MCU lowering HOLD_DCDC1 from HIGH to LOW when we tried to shutdown the PMIC.

Another problem we have that is related or not to the first problem, we get a fixed value 0X04h from the registers after the first write to PMIC. 

After a few seconds, we successfully read the values we wrote for the PMIC registers. i saw in the Logic Analyzer that the PMIC returns a fixed value of 0x04H.

registers value 

    {PMIC_TPS6572X_REG_LDO_CTRL,     0x78},    // configure LDO for 2.8V

    {PMIC_TPS6572X_REG_DEFDCDC1,     0x64},    // configure DC for 1.8V

    {PMIC_TPS6572X_REG_IRMASK2,     ~0x03},    // enable button

    {PMIC_TPS6572X_REG_CHGCONFIG0,     0x8F},    // Maximum charge current = 1C (150mAh)

    {PMIC_TPS6572X_REG_CHGCONFIG3,     0xE0},    // MAX CHARGE VOLTAGE = 4.35V

    {PMIC_TPS6572X_REG_GPIO_SSC,     0x0F},        // LEDs

    {PMIC_TPS6572X_REG_GPIO_DIR,     0xF3},        // LEDs

best regards,

kobi

  • 0
    TI__Genius 12735 points

    Hi Kobi,

    The expert for this device was out of office today and will provide an update on your question by the end of the day tomorrow. 

    Best regards,

    Layne J

  • 0
    TI__Mastermind 30280 points

    kobi kiviti said:

    i failed to put the PMIC into shutdown mode by lowering HOLD_DCDC1 from HIGH to LOW state after successful power up (powered from battery, PB_IN pulled LOW for ~1 sec).

    HOLD_DCDC1 has 100K pull-up resistor to DC2DC output and i saw in the oscilloscope that the MCU lowering HOLD_DCDC1 from HIGH to LOW when we tried to shutdown the PMIC.

    I do not understand the problem. Please try to re-phrase your question. 

    Also, please verify that Battery is the only power supply in your system. If AC-DC adapter supplies power to the device, it is impossible to shut down using HOLD_DCDC1 pin.

    kobi kiviti said:
    After a few seconds, we successfully read the values we wrote for the PMIC registers. i saw in the Logic Analyzer that the PMIC returns a fixed value of 0x04H.

    Did you ever read any values from PMIC registers other than 0x04? I need to see the datalogs from your I2C analyzer to understand the issue.

  • 0 in reply to Brian Berner
    Prodigy 30 points

    Hi Brian,

    i can't power-down the step-down converter,

    to turn ON the PMIC we pulled HIGH the HOLD_DCDC1 while the PB_IN is press and the PMIC turn ON as expected.

    to power-down (shutdown) the step-down converter i pull LOW the HOLD_DCDC1 input pin but the buck converter does not turn off.

    What am I doing wrong?

    Brian Berner said:
    Did you ever read any values from PMIC registers other than 0x04?

    We succeed in writing and reading, the problem that for the first time after writing to the registers the PMIC returns the value 0X04 and in all other times it returns the correct values.

  • 0 in reply to kobi kiviti
    TI__Mastermind 30280 points

    kobi kiviti said:
    to power-down (shutdown) the step-down converter i pull LOW the HOLD_DCDC1 input pin but the buck converter does not turn off.

    Please share a schematic and an oscilloscope capture showing AC, BAT, HOLD_DCDC1, and VDCDC1 nets. 

    If a voltage is applied at AC, then HOLD_DCDC1 is not used: DCDC1 is always on when AC power is applied.