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[FAQ] BQ76952: Common questions for OTP programming with the Bq769x2 Device Family

Part Number: BQ76952
Other Parts Discussed in Thread: BQ76942

What are key things to be aware of for OTP programming for the BQ769x2 devices?

  • The BQ769x2 device family has OTP memory which can be used to modify the device default settings. This can be useful to configure important device settings on the production line.

    When should OTP be used?

    For many applications, OTP programming is not needed. The device registers can be written by the host microcontroller during startup. This method is used in the Microcontroller code examples and shown in the microcontroller programming video. However, there are some cases where production OTP programming might be needed:

    • If the REG1 or REG2 LDOs need to be configured to be enabled at startup. Often, REG1 is used to power the microcontroller in many systems. However, even in this case, the user should check the Device Comparison Table in the datasheet since there are pre-configured part numbers that have REG1 enabled. For example, the BQ7695202 has REG1 enabled and set to 3.3V by default. 
    • If the communication mode needs to be changed. Once again, there are a few pre-configured options available in the Device Comparison Table, so ordering a pre-configured device may be a better option than setting up OTP programming in production.
    • If the device is being used in stand-alone mode. Some applications will not use a microcontroller. In this case, it is important to program the device settings in OTP so that it can operate in stand-alone mode.

    What are the hardware requirements to program OTP?

    In order to program OTP, 10-12 V must be applied to the BAT pin and the highest VCx pin (i.e. VC16 for the BQ76952, VC10 for the BQ76942). Otherwise the device will not allow OTP programming. This means that the battery cells should not be connected when programming the OTP.

    What are the software steps that should be used to program the OTP?

    The software steps are listed in Section 3 of the BQ769x2 Calibration and OTP Programming Guide. This document also describes limitations for how many times the OTP can be written.

    I am using the SUV Permanent Fail in my system along with a fuse. How do I prevent my fuse from being blown after I program the OTP using the low 10-12 V supply?

    The best way to work around any Permanent Failures that may be triggered during OTP programming is to modify the RAM register after the OTP_WRITE() command before exiting CONFIG_UPDATE mode. More detailed steps are outlined in this thread.

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