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Original question:

BQ76952: BQ76952

BQ76952: question about BQ76952PFBR

Jimmy Huang
Genius 3495 points
Part Number: BQ76952

Tool/software:

hello:

The customer's industrial and commercial storage project uses BQ76952PFBR chip, and the setup time for restart is 4.7us,


As shown in the above figure, at a frequency of 100k, the rise time here is already about 500ns, which is not slow anymore. However, this time is still not sufficient. Do you have any opinions or suggestions?

This is the peripheral of the chip

  • 0
    TI__Genius 17645 points

    Hello Jimmy,

    The BQ76952 device will initially power up by default in 400kHz I2C mode. From Table 7.28 Timing Requirements – I2C Interface, 400kHz Mode in the datasheet, the tSU:STA is ~600 ns.

    Did you change from the 400kHz mode to the 100kHz mode? If not, Section 9.2 I2C Communications Subsystem in the BQ76952 Technical Reference Manual helps show how to swap to it.

    Looking at your schematic from what you’ve shared, usually we have the resistors to SDA/SCL be 10kOhms with no capacitors there as well. The RCs there could also be causing issues/difference in expected timing.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Genius 3495 points

    Hello Alexis：

    Sorry, your response is a bit off topic and not the answer the customer wanted.

    The customer's intention is that the current frequency used in the industrial and commercial storage project is 100kHz, with a restart establishment time of 4.4us and a rise time of approximately 500ns.

    According to the specifications, the rise time meets the requirement of less than 1000ns, but the establishment time does not meet 4.7us. I would like to ask if this can be relaxed or if there are any improvement measures. Thank you!

  • 0 in reply to Jimmy Huang
    TI__Genius 17645 points

    Hello Jimmy,

    Jimmy Huang said:
    According to the specifications, the rise time meets the requirement of less than 1000ns, but the establishment time does not meet 4.7us. I would like to ask if this can be relaxed or if there are any improvement measures. Thank you!

    Are you asking if our part can have a lower repeated start time? 

    The setup repeated start time is the minimum time our part needs the MCU to provide before reading/writing again. The MCU would need to give at least that amount of time for it to be ready for another transaction.

    This is not something that can be changed to my knowledge.

    Best Regards,
    Alexis