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BQ77PL900 PROGRAMMING QUESTION

WhiteHorse
Genius 4430 points
Other Parts Discussed in Thread: BQ77PL900

Hi,

We  have a customer with the following questions regarding programming tghe BQ77PL900 EEPROM:

  1.  Does the EEPROM pin 24 require 5V to flash program the BQ chip?

  2.  If VLOG pin 32 is connected to the 3.2V VREG2, will the EEPROM program when 3.3V is applied?

Thanks for your help.

Regards,

John Wiemeyer

  • 0
    TI__Guru 54715 points

    1. The EEPROM pin is a logic write enable signal, it should have a signal level of VLOG when high.  It should be controlled according to the procedure in the datasheet Figure 23 programming flowchart.

    2. Yes, if VLOG is from VREG2, the EEPROM pin signal level should be 0 to VLOG (3.2V).  VIH min is 0.8 x VLOG

  • 0 in reply to WM5295
    Genius 4430 points

    Thanks for your reply.

  • 0 in reply to WhiteHorse
    Genius 4430 points

    One more question regarding programming.

    To program the BQ77PL900 is it possible to apply the 20V to BAT & PACK without resistors between each VC connection to evenly drop the 20V between the VC pins?

    Thanks,

    John

  • 0 in reply to WhiteHorse
    TI__Guru 54715 points

    If the VCx inputs are separate from the BAT pin and/or all remain low, this should be OK.  If you don't control the voltage on the VCx pins the 20V could distribute to give a damaging voltage on one or more inputs.

    See page 36 of the datasheet and http://e2e.ti.com/support/power_management/battery_management/w/design_notes/478.bq77pl900-eeprom-programming-voltage-application.aspx 

  • 0 in reply to WM5295
    Genius 4430 points

    Here is what the customer finally implemented.

    They have an external fuse between BAT pin 9 and PACK pin 47.  Figure 23 does say that the 20V for EEPROM Programming can be applied to BAT or PACK so they applied it to PACK.  The voltage measured on every VC pin is close to GND potential this way.

    The EV2300 does a great job with the EEPROM Program timing requirements so they just added a circuit to change the VOUT drive from 0 - 5V to 0 – 3.3V.  Now the standard BQ77PL900 Evaluation software program with the EV2300 is working fine for configuration review and for the EEPROM programming.

    The default program is 00, 00, 00, 00, 00.                                                  

    To optimize performance for the battery cells with their two products they modified the program to;

    0A, 0F, 04, E3, 10

    This is the method & program they will use to test & program the BMS before cells are attached.  If you see any problems with this please let me know.

    Thanks for your help.

    Regards,

    John