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TPS65217: channel(DCDC,LDO) behavior when Vbat is low voltage

kura
Genius 4680 points
Part Number: TPS65217

Please let us know channel(DCDC,LDO) behavior that is 3.3V setup,when Vbat is 2.75V to 3.3V.

  • 0
    TI__Intellectual 810 points

    Hi Kura,

    There are a lot of factor that contribute to the behavior of the DCDC converters and LDOs in the system. Could you provide a few more details?

    The input voltage range of 2.75V to 3.3V is well within the specifications of the part for the LDO's and DCDC converters. My only concern would be due to any line transient, they could cause a large enough voltage drop on the input to trigger a UVLO condition, assuming you only have BAT connected and are operating at 2.75V, USB and AC not connected. Also, LDO will not automatically enter a WAIT PWR_EN state if AC and USB connections are not present but BAT is. You must then pull PB_IN low for LDO1 to enter WAIT PWR_EN state.

    -Raymundo Hernandez-Toscano

  • 0 in reply to Raymundo Hernandez-Toscano
    Genius 4680 points
    My concern is
    When The input voltage range of 2.75V to 3.3V ,what voltage Vout(3.3Vout set by I2C) become .
    Because DCDC of this IC is buck topology.
  • 0 in reply to kura
    Genius 4680 points
    Raymundo-san
    Thank you for your reply.
    Any update for this ?
  • 0 in reply to kura
    Genius 4680 points

    Load Information.xlsxWe got load information from customer .

    Please check attached and advise us.

  • 0 in reply to kura
    Genius 4680 points
    We got additional information from customer.

    AC adapter:5V to 9V
    Battery Voltage:3V to 4.2V
  • 0 in reply to kura
    TI__Intellectual 810 points
    Hi Kura,

    The recommended AC supply voltage range is 4.3V-5.8V for valid charging. Despite the 20V absolute maximum rating for AC, the LDO's have maximum input voltage of 5.8V. Do you plan to run the LDO's off of one of the buck rails? The input voltage range for Bat seems perfectly fine. I don't see an issue with DCDC1/2/3 regulating 3.3V out, assuming VSYS>=3.3V. Also, to enable the converters to regulate 3.3V you would need to contact the factory to provide you with that option. The LDO1/2 can regulate the 3.3V that you inquired about but keep in mind that they have maximum dropout voltage of 200mV. This would mean that your input voltage for the LDO's would need to be at least 200mV above your intended output. Also, note that the min/max voltage difference between SYS and any VIN_DCDCx or SYS and VINLDO is 300mV. If the AC voltage exceeds 6.5V then the system changes to VBat, once the AC voltage falls bellow 6.5V the system will revert back to AC. I am not sure if I answered your question. When you refer to the behavior are your referring to its line/load regulation, and transient behavior at 3.3Vin and 3.3Vout? The voltage ripple is based on a few parameter and can be calculated using the equation provided in section 10.2.2.1.2.

    -Raymundo Hernandez-Toscano
  • 0 in reply to Raymundo Hernandez-Toscano
    Genius 4680 points

    When Battery voltage down to 3V,please let us know What 3.3V output become.

  • 0 in reply to kura
    TI__Intellectual 810 points

    Kura,

    I apologize for the delay. I can attempt to run the use case you are describing in the lab, and provide results as soon as possible. However, given the use case, if you provide a 3V input or the battery drains to 3V on the DCDC converters and attempt to regualte at 3.3V, I suspect that the converter would drop out of regulation. Also, given your UVLO setting and AC/USB not present to charge the battery or is not within the charging input range then the regulator would drop our of regulation or become unstable. When I looked at the load profile you provided earlier in the thread, I made the assumption that regulator No5 and No6 were both bucks. However, I wasn't entirely sure if you plan to split load between both rails. Can you provide me with each rail's requirements/load and power tree?

    -Raymundo Hernandez-Toscano