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BQ25750: Request for Calculation sheet

Jeevabharathi R
Prodigy 130 points
Part Number: BQ25750

Tool/software:

Hi Team,

We are planning to use BQ25750 battery charger IC in our design. Can you please share if any calculation sheet available for this battery charger IC?

Thanks

  • 0
    TI__Mastermind 31305 points

    Hello Jeevabharathi,

    Yes, we do have a design calculator for this IC: www.ti.com/.../

    We also have an FAQ for this IC as well: e2e.ti.com/.../faq-bq2575x-faq-page

    Let me know if you have any questions about this.

    Best Regards,
    Ethan Galloway

  • 0
    Prodigy 130 points

    Hi Ethan, 

    Can you please confirm, Is it necessary to use only this 103AT-2 NTC to achive the cool and warm temperature threshold limit for BQ25750?

    In our battery pack have 10K NTC with the B = 3435K 

    We need to configure the charging profile to the below value

    20% Ichg at T1 - T2 ( 0C to 15 C),

    100% Ichg at (15C- 50C)

    40% at T3 - T5 (50 - 60C )

    above T5 (60C) charge suspend.

  • 0
    Prodigy 130 points

    Hi Ethan, 

    Can you please confirm, Is it necessary to use only this 103AT-2 NTC to achive the cool and warm temperature threshold limit for BQ25750?

    In our battery pack have 10K NTC with the B = 3435K 

    We need to configure the charging profile to the below value

    20% Ichg at T1 - T2 ( 0C to 15 C),

    100% Ichg at (15C- 50C)

    40% at T3 - T5 (50 - 60C )

    above T5 (60C) charge suspend.

  • 0
    Prodigy 130 points

    Hi Ethan, 

    Can you please confirm, Is it necessary to use only this 103AT-2 NTC to achive the cool and warm temperature threshold limit for BQ25750?

    In our battery pack have 10K NTC with the B = 3435K 

    We need to configure the charging profile to the below value

    20% Ichg at T1 - T2 ( 0C to 15 C),

    100% Ichg at (15C- 50C)

    40% at T3 - T5 (50 - 60C )

    above T5 (60C) charge suspend.

  • 0 in reply to Jeevabharathi R
    TI__Mastermind 31305 points

    Hello Jeevabharathi,

    Jeevabharathi R said:
    Can you please confirm, Is it necessary to use only this 103AT-2 NTC to achive the cool and warm temperature threshold limit for BQ25750?

    It is possible to use different temperature sense resistor. The sense resistor you have has the same B and resistance as the 103AT-2 NTC.

    You can use the design calculator to get the recommended values for the top and bottom resistors.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 130 points

    Ethan

    Thank you for your information.

    We are planning to use the internal ADC of BQ25750 to monitoring input power. Could you please provide information regarding the accuracy of the internal ADC in measuring the input current and the voltage?

  • 0 in reply to Jeevabharathi R
    TI__Mastermind 31305 points

    Hello Jeevabharathi,

    Your welcome.

    The ADC of the BQ25750 is intended for use as a general indicator. Please keep in mind that we don't provide a datasheet specification of the accuracy for the ADCs. Here's an FAQ that goes into more detail on how to use the ADC.

    Here's the IAC ADC accuracy that was measured:

    Here's the VAC ADC accuracy that was measured:

    Also, the accuracy of the IAC ADC should be improved by going to a larger 10mΩ input sense resistor.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 130 points

    Hi Ethan,

    Thank you for reply,

    Could you please clarify my doubt? When using the internal gate drive voltage, is it necessary to externally connect VREG to BTST1 and BTST2 through a diode, or is it sufficient to connect VREG to DRV_SUP, which is internally connected within the IC.

    Thank you

  • 0 in reply to Jeevabharathi R
    TI__Expert 6545 points

    Hi Jeevabharathi,

    DRV_SUP needs to be connected to BTST1 and BTST2 externally through a Schottky diode. This is because the capacitor is referenced to the SW node, which will be switching between a high and low voltage. This capacitor is necessary to drive the HIDRVx pins above the maximum voltage in the circuit to turn on the MOSFETs. When the SWx node voltage rises, so will the voltage on the capacitor to the BTSTx pin, this could cause a short to the DRV_SUP pin if the reverse path is not blocked by a Schottky diode.

    Let me know if this explanation is unclear.

    Best regards,
    Michael Bradbourne

  • 0 in reply to Michael Bradbourne
    Prodigy 130 points

    Hi Michael,

    Thank you for the clarification.

    I have a few follow-up questions regarding the gate driver configuration for the BQ25750:

    1. Internal Gate Driver Supply: The datasheet mentions that the BQ25750 includes a 5V internal gate driver for the buck-boost converter. If we plan to use this internal supply, what is the recommended connection configuration?

    2. Internal LDO as Gate Driver: In the case where the internal LDO is used as the gate driver supply, how should the DRV_SUP, BTSTX, and VREG pins be interconnected?

    Thank you 

  • 0 in reply to Jeevabharathi R
    TI__Mastermind 31305 points

    Hello Jeevabharathi,

    Thanks for being patient with this. I'm coming back from a vacation. Quick clarification on the BTST diode. The BQ25750 does not have an internal BTST diode to supply the BTST voltage for the converter. The BTST diode will be needed when using REGN as the gate drive voltage or external gate drive voltage.

    Also, the internal gate drive supply and the internal LDO are the same source. Both of these refer to REGN. Thanks for being patient with the multiple terms here.

    For the pin connections, I recommend referring to the BQ25750 schematic and layout checklist or the BQ25750 EVM schematics. Just for reference, we also have a general FAQ for the BQ25750 part family.

    Let me know if you have any other questions.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 130 points

    Hi Ethan Galloway,

    The datasheet mentions that IPRECHG_MAX is 20% of ICHG_MAX. However, there's also a register called REG0x10_Precharge_Current_Limit, which by default sets IPRECHG to 4000mA (0x50h).

    So, which value is actually used for precharge current — the 20% of ICHG_MAX or the default register value?

  • 0 in reply to Jeevabharathi R
    TI__Mastermind 31305 points

    Hello Jeevabharathi,

    Jeevabharathi R said:
    So, which value is actually used for precharge current — the 20% of ICHG_MAX or the default register value?

    The IC will lose the lowest value of the precharge current for the actual current.

    Best Regards,
    Ethan Galloway