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BQ32000: Implement BQ32000 in 5V system

Gabriel Xu
Intellectual 2045 points
Part Number: BQ32000

Hi teams

Customers trying to use BQ32000 in their 5V system products(water heater)

As BQ32000 is powered by 3.3V a voltage regulator is needed in this case.

In order to save LDO cost, we are planning to use a resistor divider to generate 3.3V for BQ32000.

My questions:

  1. Any potential risk for this structure?
  2. The supply current BQ32000 needed? (In datasheet chapter 6.5 I found Icc is about 0.1mA. I want to double confirm 100uA is enough for BQ32000)
  3. What's the minimum voltage BQ32000 could work when it powered by a backup supply? (Is 1.4V or 2V?)
  4. BQ32000 communicated with 5V MCU with I2C interface. If I pull-up I2C interface to 3.3V, could we connect to MCU directly without a level shifter? Will MCU signal with 5V voltage level damage BQ32000? (I am not sure what voltage level BQ32000 will see as we pull-up the bus to 3.3V)
  5. I noticed that BQ32000 could charge the backup supply internally, I wondering to know how much current it could handle during the charge?

  • 0
    TI__Intellectual 2045 points

    Hi teams

    Looking forward to your reply

  • 0 in reply to Gabriel Xu
    TI__Genius 16845 points

    A1. The structure is not commonly used, but I do not anticipate risks with appropriate values for the pullup and pulldown resistor. With a Rt = 1K and Rb = 2K, you would get 3.33V and current in the voltage divider of 1.67mA is larger than the 0.1mA operating current. Be mindful to adhere to datasheet section 8.2.2.3 Utilizing the Backup Supply.

    A2. The supply current is 100uA when operating from the core supply Vcc

    A3. 1.4V

    A4. Table 6.1 indicates that the pin voltages should not exceed Vcc + 0.3 V. Interfacing with 5V will exceed device ratings and therefore I would recommend to use the level shifter.

    A5. The trickle charger circuit is shown in Figure 6. The current from the charger will depend on whether fast charge is enabled (TCFE bit) and the voltage of the backup supply Vback. Recommended to use fast charge mode when the Vback voltage is larger than Vcc - 0.7V. For how much current the backup supply can withstand, consult the datasheet for the supercapacitor or trickle charger datasheet.

    Kind regards,
    Lane