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BQ25792: BQ25792 charging with consumption current only

Ahmed HRABI
Prodigy 10 points
Part Number: BQ25792
Other Parts Discussed in Thread: TPS25751, , TPS25750

Tool/software:

Hi all,

I am using a BQ25792 with a TPS25751 to charge a 4-cell battery (20V). The ICHG is set to 2.5A, but the actual charging current is determined by the card's consumption. For example, if the card consumes 200mA, the charger will only output 200mA, and similarly for 300mA.

  • The charging state is fast charge.
  • The ICHG is 2.5A
  • The charge is enabled.

I note that on anotherr card withe same charge adapter but with TPS25750 i don't have the problem. The communication between the BQ25 and the TPS25751 is valid and i have verified the registers configurations with I2C.

This is what i read from the BQ25792 registers:

[BQ25] : REG00_VSYSMIN: 24
[BQ25] : REG01_VREG: 1680
[BQ25] : REG03_ICHG: 250
[BQ25] : REG05_VINDPM: 190
[BQ25] : REG06_IINDPM: 300
[BQ25] : REG08_VBAT_LOWV: 0
[BQ25] : REG08_IPRECHG: 4
[BQ25] : REG09_REG_RST: 0
[BQ25] : REG09_ITERM: 2
[BQ25] : REG0A_CELL: 3
[BQ25] : REG0A_TRECHG: 2
[BQ25] : REG0A_VRECHG: 1
[BQ25] : REG0B_VOTG: 234
[BQ25] : REG0D_PRECHG_TMR: 0
[BQ25] : REG0D_IOTG: 23
[BQ25] : REG0E_TOPOFF_TMR: 0
[BQ25] : REG0E_EN_TRICHG_TMR: 1
[BQ25] : REG0E_EN_PRECHG_TMR: 1
[BQ25] : REG0E_EN_CHG_TMR: 1
[BQ25] : REG0E_CHG_TMR: 0
[BQ25] : REG0E_TMR2X_EN: 0
[BQ25] : REG0F_EN_AUTO_IBATDIS: 1
[BQ25] : REG0F_FORCE_IBATDIS: 0
[BQ25] : REG0F_EN_CHG: 1
[BQ25] : REG0F_EN_ICO: 0
[BQ25] : REG0F_FORCE_ICO: 0
[BQ25] : REG0F_EN_HIZ: 0
[BQ25] : REG0F_EN_TERM: 1
[BQ25] : REG10_VAC_OVP: 0
[BQ25] : REG10_WD_RST: 0
[BQ25] : REG10_WATCHDOG: 0
[BQ25] : REG11_FORCE_INDET: 0
[BQ25] : REG11_AUTO_INDET_EN: 0
[BQ25] : REG11_EN_12V: 0
[BQ25] : REG11_EN_9V: 0
[BQ25] : REG11_HVDCP_EN: 0
[BQ25] : REG11_SDRV_CTRL: 0
[BQ25] : REG11_SDRV_DLY: 0
[BQ25] : REG12_DIS_ACDRV: 0
[BQ25] : REG12_EN_OTG: 0
[BQ25] : REG12_PFM_OTG_DIS: 0
[BQ25] : REG12_PFM_FWD_DIS: 0
[BQ25] : REG12_WKUP_DLY: 0
[BQ25] : REG12_DIS_LDO: 0
[BQ25] : REG12_DIS_OTG_OOA: 0
[BQ25] : REG12_DIS_FWD_OOA: 0
[BQ25] : REG13_EN_ACDRV2: 0
[BQ25] : REG13_EN_ACDRV1: 0
[BQ25] : REG13_PWM_FREQ: 1
[BQ25] : REG13_DIS_STAT: 0
[BQ25] : REG13_DIS_VSYS_SHORT: 0
[BQ25] : REG13_DIS_VOTG_UVP: 0
[BQ25] : REG13_FORCE_VINDPM: 0
[BQ25] : REG13_EN_IBUS_OCP: 1
[BQ25] : REG14_SFET_PRESENT: 0
[BQ25] : REG14_EN_IBAT: 0
[BQ25] : REG14_IBAT_REG: 3
[BQ25] : REG14_EN_IINDPM: 1
[BQ25] : REG14_EN_EXTILIM: 0
[BQ25] : REG14_EN_BATOC: 0
[BQ25] : REG16_TREG: 3
[BQ25] : REG16_TSHUT: 1
[BQ25] : REG16_VBUS_PD_EN: 0
[BQ25] : REG16_VAC1_PD_EN: 0
[BQ25] : REG16_VAC2_PD_EN: 0
[BQ25] : REG17_JEITA_VSET_2: 3
[BQ25] : REG17_JEITA_ISETH_1: 3
[BQ25] : REG17_JEITA_ISETC_1: 1
[BQ25] : REG18_TS_COOL_1: 1
[BQ25] : REG18_TS_WARM_1: 3
[BQ25] : REG18_BHOT_1: 1
[BQ25] : REG18_BCOLD: 0
[BQ25] : REG18_TS_IGNORE: 0
[BQ25] : REG19_ICO_ILIM: 300
[BQ25] : REG1B_IINDPM_STAT: 0
[BQ25] : REG1B_VINDPM_STAT: 0
[BQ25] : REG1B_WD_STAT: 0
[BQ25] : REG1B_POORSRC_STAT: 0
[BQ25] : REG1B_PG_STAT: 1
[BQ25] : REG1B_AC2_PRESENT_STAT: 1
[BQ25] : REG1B_AC1_PRESENT_STAT: 1
[BQ25] : REG1B_VBUS_PRESENT_STAT: 1
[BQ25] : REG1C_CHG_STAT: 3
[BQ25] : REG1C_VBUS_STAT: 8
[BQ25] : REG1C_BC1_2_DONE_STAT: 0
[BQ25] : REG1D_ICO_STAT: 0
[BQ25] : REG1D_TREG_STAT: 0
[BQ25] : REG1D_DPDM_STAT: 0
[BQ25] : REG1D_VBAT_PRESENT_STAT: 1
[BQ25] : REG1E_ACRB2_STAT: 0
[BQ25] : REG1E_ACRB1_STAT: 0
[BQ25] : REG1E_ADC_DONE_STAT: 0
[BQ25] : REG1E_VSYS_STAT: 0
[BQ25] : REG1E_CHG_TMR_STAT: 0
[BQ25] : REG1E_TRICHG_TMR_STAT: 0
[BQ25] : REG1E_PRECHG_TMR_STAT: 0
[BQ25] : REG1F_VBATOTG_LOW_STAT: 0
[BQ25] : REG1F_TS_COLD_STAT: 0
[BQ25] : REG1F_TS_COOL_STAT: 0
[BQ25] : REG1F_TS_WARM_STAT: 0
[BQ25] : REG1F_TS_HOT_STAT: 0
[BQ25] : REG20_IBAT_REG_STAT: 0
[BQ25] : REG20_VBUS_OVP_STAT: 0
[BQ25] : REG20_VBAT_OVP_STAT: 0
[BQ25] : REG20_IBUS_OCP_STAT: 0
[BQ25] : REG20_IBAT_OCP_STAT: 0
[BQ25] : REG20_CONV_OCP_STAT: 0
[BQ25] : REG20_VAC2_OVP_STAT: 0
[BQ25] : REG20_VAC1_OVP_STAT: 0
[BQ25] : REG21_VSYS_SHORT_STAT: 0
[BQ25] : REG21_VSYS_OVP_STAT: 0
[BQ25] : REG21_OTG_OVP_STAT: 0
[BQ25] : REG21_OTG_UVP_STAT: 0
[BQ25] : REG21_TSHUT_STAT: 0
[BQ25] : REG22_IINDPM_FLAG: 0
[BQ25] : REG22_VINDPM_FLAG: 0
[BQ25] : REG22_WD_FLAG: 0
[BQ25] : REG22_POORSRC_FLAG: 0
[BQ25] : REG22_PG_FLAG: 0
[BQ25] : REG22_AC2_PRESENT_FLAG: 0
[BQ25] : REG22_AC1_PRESENT_FLAG: 0
[BQ25] : REG22_VBUS_PRESENT_FLAG: 0
[BQ25] : REG23_CHG_FLAG: 0
[BQ25] : REG23_ICO_FLAG: 0
[BQ25] : REG23_VBUS_FLAG: 0
[BQ25] : REG23_TREG_FLAG Turbine: 0
[BQ25] : REG23_VBAT_PRESENT_FLAG: 0
[BQ25] : REG23_BC1_2_DONE_FLAG: 0
[BQ25] : REG24_ADC_DONE_FLAG: 0
[BQ25] : REG24_VSYS_FLAG: 0
[BQ25] : REG24_CHG_TMR_FLAG: 0
[BQ25] : REG24_TRICHG_TMR_FLAG: 0
[BQ25] : REG24_PRECHG_TMR_FLAG: 0
[BQ25] : REG24_TOPOFF_TMR_FLAG: 0
[BQ25] : REG25_VBATOTG_LOW_FLAG: 0
[BQ25] : REG25_TS_COLD_FLAG: 0
[BQ25] : REG25_TS_COOL_FLAG: 0
[BQ25] : REG25_TS_WARM_FLAG: 0
[BQ25] : REG25_TS_HOT_FLAG: 0
[BQ25] : REG26_IBAT_REG_FLAG: 0
[BQ25] : REG26_VBUS_OVP_FLAG: 0
[BQ25] : REG26_VBAT_OVP_FLAG: 0
[BQ25] : REG26_IBUS_OCP_FLAG: 0
[BQ25] : REG26_IBAT_OCP_FLAG: 0
[BQ25] : REG26_CONV_OCP_FLAG: 0
[BQ25] : REG26_VAC2_OVP_FLAG: 0
[BQ25] : REG26_VAC1_OVP_FLAG: 0
[BQ25] : REG27_VSYS_SHORT_FLAG: 0
[BQ25] : REG27_VSYS_OVP_FLAG: 0
[BQ25] : REG27_OTG_OVP_FLAG: 0
[BQ25] : REG27_OTG_UVP_FLAG: 0
[BQ25] : REG27_TSHUT_FLAG: 0
[BQ25] : REG28_IINDPM_MASK: 0
[BQ25] : REG28_VINDPM_MASK: 0
[BQ25] : REG28_WD_MASK: 0
[BQ25] : REG28_POORSRC_MASK: 0
[BQ25] : REG28_PG_MASK: 0
[BQ25] : REG28_AC2_PRESENT_MASK: 0
[BQ25] : REG28_AC1_PRESENT_MASK: 0
[BQ25] : REG28_VBUS_PRESENT_MASK: 0
[BQ25] : REG29_CHG_MASK: 0
[BQ25] : REG29_ICO_MASK: 0
[BQ25] : REG29_VBUS_MASK: 0
[BQ25] : REG29_TREG_MASK: 0
[BQ25] : REG29_VBAT_PRESENT_MASK: 0
[BQ25] : REG29_BC1_2_DONE_MASK: 0
[BQ25] : REG2A_DPDM_DONE_MASK: 0
[BQ25] : REG2A_ADC_DONE_MASK: 0
[BQ25] : REG2A_VSYS_MASK: 0
[BQ25] : REG2A_CHG_TMR_MASK: 0
[BQ25] : REG2A_TRICHG_TMR_MASK: 0
[BQ25] : REG2A_PRECHG_TMR_MASK: 0
[BQ25] : REG2A_TOPOFF_TMR_MASK: 0
[BQ25] : REG2B_VBATOTG_LOW_MASK: 0
[BQ25] : REG2B_TS_COLD_MASK: 0
[BQ25] : REG2B_TS_COOL_MASK: 0
[BQ25] : REG2B_TS_WARM_MASK: 0
[BQ25] : REG2B_TS_HOT_MASK: 0
[BQ25] : REG2C_IBAT_REG_MASK: 0
[BQ25] : REG2C_VBUS_OVP_MASK: 0
[BQ25] : REG2C_VBAT_OVP_MASK: 0
[BQ25] : REG2C_IBUS_OCP_MASK: 0
[BQ25] : REG2C_IBAT_OCP_MASK: 0
[BQ25] : REG2C_CONV_OCP_MASK: 0
[BQ25] : REG2C_VAC2_OVP_MASK: 0
[BQ25] : REG2C_VAC1_OVP_MASK: 0
[BQ25] : REG2D_VSYS_SHORT_MASK: 0
[BQ25] : REG2D_VSYS_OVP_MASK: 0
[BQ25] : REG2D_OTG_OVP_MASK: 0
[BQ25] : REG2D_OTG_UVP_MASK: 0
[BQ25] : REG2D_TSHUT_MASK: 0
[BQ25] : REG2E_ADC_EN: 1
[BQ25] : REG2E_ADC_RATE: 0
[BQ25] : REG2E_ADC_SAMPLE: 0
[BQ25] : REG2E_ADC_AVG: 0
[BQ25] : REG2E_ADC_AVG_INIT: 0
[BQ25] : REG2F_IBUS_ADC_DIS: 0
[BQ25] : REG2F_IBAT_ADC_DIS: 0
[BQ25] : REG2F_VBUS_ADC_DIS: 0
[BQ25] : REG2F_VBAT_ADC_DIS: 0
[BQ25] : REG2F_VSYS_ADC_DIS: 0
[BQ25] : REG2F_TS_ADC_DIS: 0
[BQ25] : REG2F_TDIE_ADC_DIS: 0
[BQ25] : REG30_DP_ADC_DIS: 0
[BQ25] : REG30_DM_ADC_DIS: 0
[BQ25] : REG30_VAC2_ADC_DIS: 0
[BQ25] : REG30_VAC1_ADC_DIS: 0
[BQ25] : REG31_IBUS_ADC_15_0: 220
[BQ25] : REG33_IBAT_ADC_15_0: 0
[BQ25] : REG35_VBUS_ADC_15_0: 20206
[BQ25] : REG37_VAC1_ADC_15_0: 20197
[BQ25] : REG39_VAC2_ADC_15_0: 20227
[BQ25] : REG3B_VBAT_ADC_15_0: 13900
[BQ25] : REG3D_VSYS_ADC_15_0: 14127
[BQ25] : REG3F_TS_ADC_15_0: 437
[BQ25] : REG41_TDIE_ADC_15_0: 69
[BQ25] : REG43_D_PLUS_ADC_15_0: 93
[BQ25] : REG45_D_MINUS_ADC_15_0: 134
[BQ25] : REG47_DPDM_DAC_DPLUS_2_0: 0
[BQ25] : REG47_DPDM_DAC_DMINUS_2_0: 0
[BQ25] : REG48_PART_INF_PN_2_0: 1
[BQ25] : REG48_PART_INF_DEV_REV_2_0: 0

regards, 

HRABI.

  • 0
    TI__Guru**** 166896 points

    HI HRABI,

    The PD controller firmware changed slightly from 750 to 751.  I think one item that changed was the VBATLOWV setting, which determines when the charger switches from precharge to fast charge.  The precharge current levels are closer to the card levels you want. Your registers above show VBATLOWV=15%*BATREG which essentially means the charger skips precharge and goes straight to fast charge.  The ADC shows VBAT=13.9V so the charger is in fast charge for sure.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hi Jeff,

    Thanks for your reply.
    Switching to fast charge was intentional, but I don't understand the connection between this and our main issue: the actual charge current is limited to the system consumption (around 200 mA), instead of the 2.5 A configured through ICHG when we are in fast charge mode.

    Regards, 

    HRABI.

  • 0 in reply to Ahmed HRABI
    TI__Guru**** 166896 points

    Hi HRABI,

    I think I misunderstood. So you do have a battery connected at BAT pin and its voltage, as sensed by BATP, is < VREG setting?  If so, then the battery should accept the charge current per the ICHG or PRECHG as long as both CE pin and bit have charge enabled and no TS pin fault.  Your bits do not indicate supplement mode since VSYS>VBAT or other fault like TS fault that would reduce charge current.  

    If you power the charger directly with a bench power supply instead of TPS2575x, does it charge correctly?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hello Jeff,

    Replacing the TPS2575 with the bench power supply does not change the charging current value.

    Regards,
    HRABI

  • 0 in reply to Ahmed HRABI
    TI__Guru**** 166896 points

    Hi HRABI,

    Then I need some scopes shots of VBUS, VSYS, VBAT and SW1 when you see the issue.  Please zoom in enough so that see individual switching pulses on SW1.

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Prodigy 10 points

    Hello Jeff,

    With our new board, we removed the ShipFET and connected SDRV to VBAT as indicated in the datasheet: "Connect [...] SDRV to BAT when the ship FET is not used."
    However, while investigating the cause of our issue on our prototype—where the charger was working—we made this connection, and the BQ no longer charges.
    We did make sure to uncheck the "SHIPFET Present?" box in the TI CHARGER GUI.
    Do you know if the charger can operate with VBAT connected to SDRV, or could this be an error in the BQ25792 documentation?
    Thank you!

    Regards,
    HRABI

  • +1 in reply to Ahmed HRABI
    TI__Guru**** 166896 points

    Hi HRABI,

    The charger should still function with SDRV=BAT but we found recently that max charge current may be limited due to noise injection into the BATFET current sense circuity.  So in a soon to release datasheet update, we only recommend connecting SDRV to ground through a 1000pF capacitor, like on the EVM.

    Regards,

    Jeff