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BQ76925: Unknown Component Values

Natasha Evans
Prodigy 20 points
Part Number: BQ76925

We're designing a battery management board based on this schematic (refer to Figure 1, page 4) for the BQ7625 and the MSP430G2xx2. In designing the schematic, we ran into a few components which we were unsure about:

  • What are NA components? (Specifically, we were wondering about R30 in the load removal circuit.)
  • Should we place the zero-ohm resistors, or could those be approximated using a wire? (For example, R11 and R12 are marked as having zero resistance.)
  • D5 in the hold-up circuit has double lines -- is this any different than a regular zener diode?
  • How should we select RIN values depending on our power consumption and application?
  • How does RSENS1/RSENS2 parallel resistors differ from a single resistor in the current sensor circuit? (see picture below)
  • What are SMBUS and COM in the Display Button Detection circuit?

Also, the table below is a list of obsolete/unavailable components (the component numbers refer to the circuit diagram in the linked datasheet). Are there any recommended alternatives to replace these components?

Thanks for your help!

  • 0
    TI__Mastermind 42060 points

    Hello Natasha,

    • What are NA components? (Specifically, we were wondering about R30 in the load removal circuit.)
      I am not sure what this resistance is. We do not have this in our EVM, it may just be a resistor to create a voltage divider in order to adjust the voltage for the ADC.
    • Should we place the zero-ohm resistors, or could those be approximated using a wire? (For example, R11 and R12 are marked as having zero resistance.)
      These zero-ohm resistors are essentially jumpers. If you require the connection and are sure of it, it can be replaced by a wire.
    • D5 in the hold-up circuit has double lines -- is this any different than a regular zener diode?
      It is an unidirectional TVS diode for ESD protection to protect the IC. D4 is used to clamp the voltage going in, probably to protect the pins from exceeding absolute max in transient events.
    • How should we select RIN values depending on our power consumption and application?
      RIN is selected based on cell balancing current. See Section 9.2.1 Design Requirements of the datasheet for guidance in selecting this and other components. Power consumption should be low in general, see Section 7.5 Electrical Characteristics: Supply Current of the datasheet.
    • How does RSENS1/RSENS2 parallel resistors differ from a single resistor in the current sensor circuit? (see picture below)
      Power dissipation, you place multiple in parallel depending on the power dissipation of the sense resistor based on the maximum current.
    • What are SMBUS and COM in the Display Button Detection circuit?
      SMUS is a communication protocol compatible with I2C. COM is likely communications abbreviated.

    I would advice you to read our datasheet for data on how to design the IC, also read the EVM User Guide and our Getting Started application report.

    You can look up the obsolete parts online and search for similar parts from there. You may also see our EVM BOM for more guidance.

    Best Regards,
    Luis Hernandez Salomon