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BQ34Z100-G1: Simple Reference Design

Hong Tay
Expert 2465 points
Part Number: BQ34Z100-G1

Hi Sir, Madam,

Do you have simple reference design for BQ34Z100-G1? 

My customer currently is studying the reference design for BQ34Z100-G1 EVM and realized the size can't fit their small board size application. 

Hope to hear from you soon. Thanks.

  • 0
    TI__Mastermind 25955 points
    Hi Hong,

    The EVM is quite large and full featured to allow for multiple test ranges.

    A simplified implementation schematic for the bq34z100-g1 is shown on page 46 of the datasheet (Figure 14), found here: www.ti.com/.../bq34z100-g1

    Depending on your customer's needs, the schematics may be simplified yet further through the removal of the LEDs. Depending on the requirements of your customer, this schematic can be even further simplified. What are their requirements?

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 2465 points

    Hi Bryan,

    Thanks for your kind advice. Please help to comment for my customer enquiry below.

  • 0 in reply to Hong Tay
    TI__Mastermind 25955 points
    Hi Hong,

    Most of the FETs highlighted by your customer help reduce power consumption of the device. For example, the network attacked to the BAT pin and VEN pin of the device reduce the power lost in the external voltage divider circuit connected to the BAT pin. I would suggest testing first by removing the FETS from an EVM to determine if the power consumption increase caused by the removal is acceptable to your application.

    The FET and diode structure connected to REGIN is to clamp from the battery and allow the device to be powered. The LEDS do not need to be connected (P1 and P2).

    HDQ may be used for communication, but please use I2C to program and test the device. Putting the device in HDQ mode should be one of the last steps in production.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 2465 points

    Hi Bryan,

    Thanks for the advice. My customer has further enquiry:

    1) The LEDs for P1 and P2 are required for capacity indication. Can the FETs be removed and LEDs direct connected to the pin? Any issue?

    2) Any way to trigger the LEDs blinking to indicate battery capacity? Is it possible to have 2 alternative control input to trigger the LEDs blinking, for example 1 is from battery pack and 1 is from the end device?

    Below is Maxim DS2788 which my customer using previously, there is a pin called "PIO" for the function, for your reference.

    Hope to hear from you soon. Thanks.

  • 0 in reply to Bryan Kahler
    Expert 2465 points
    Hi Bryan,

    Any advice?

    Thanks.
  • 0 in reply to Bryan Kahler
    Expert 2465 points
    Hi Bryan,

    I am still waiting for your advice.

    Thanks.
  • 0 in reply to Bryan Kahler
    Expert 2465 points
    Hi Bryan,

    Please advise. Thanks.
  • 0 in reply to Bryan Kahler
    Expert 2465 points

    Hi Bryan,

    My customer using a FET as a switch, when there is a pull high from device, it will turn on the FET then REG25 will give 2.5V to VEN pin and LED light will display to show battery capacity.

    This FET is in parallel to the push button switch for the LED display.

    Does the design need an extra protection component if switch and FET are in parallel.

    For the current limiting, a limiting resistors and a blocking diode are added.

    Hope to hear from you soon. Thanks.

    b27_bq34z100_LED.pdf

  • 0 in reply to Hong Tay
    TI__Mastermind 25955 points
    Hi Hong,

    Thank you for the schematic.

    In the EVM, the LEDs are powered from the rail feeling the REGIN pin, not P+.

    What voltage is P+ being operated at? In this configuration, please ensure that your switch is rated for the voltage, and that voltages do not exceed the maximum allowable per the pin. A debounce circuit may be required.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 2465 points

    Hi Bryan,

    Thanks for your reply.

    My customer followed below connection in the BQ34Z100-G1 datasheet for 1-cell Li-ion reference schematic.

    Voltage of P+ is from 3V-4.2V (Battery voltage)

    The switch to be used is the same as the original design using the DS2788 so it looks ok.

    May I know what is the FET rating to be used in parallel to the switch?

    Hope to hear from you soon. Thanks.

  • 0 in reply to Hong Tay
    TI__Intellectual 1365 points
    Hong, I guess you want to use the FET in parallel with SW1.
    You need very cheap and small FET which Vds > 5V and ID > 5mA.