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BQ77PL900: EEPROM programming

Gabba
Prodigy 85 points
Other Parts Discussed in Thread: BQ77PL900

Hi, I have some questions about EEPROM programming of TI's IC BQ77PL900:

In the datasheet it's written that to program EEPROM I have to supply the IC with BATT or PACK equal to 20V.

It's also said that when Vbatt and Vc are connectet togheter in the PCB Vbatt must be set to 7.5V and then (after switch on all cell balance MOSFET) increase this voltage up  to 20V.

If I want to program the EEPROM on board, do I have to disconnect batteries and attach a 20V dedicated supply???

If I can't set Vbatt at the mentioned values onboard (because of presence of batteries), I have to realize an external standalone programmer for the IC?

Sorry for my bad english, thanks for the attention.

 

ps.Have you got more documentation about EEPROM programming procedure?? 

  • 0
    TI__Guru 54715 points

    You should be able to program with cells attached and at a battery voltage >14V (and less than the device maximum).  If you can not adjust your battery voltage to >14V you should disconnect the cells and provide a power supply to device during programming.

    The 20V is a nice round number with plenty of margin for the device programming operaiton. This is a good value to use when possible. 

    When powering the part for programming it is important not to exceed the absolute maximum voltages of the pins. The procedure of powering the device at 7.5V and turning on all cell balancing transistors before increasing the voltage is to provide a method of distributing the cell voltages if VC1 and the BAT pin are not separated on the board and if the test fixture does not include resistors or some other method to distribute the "battery" voltage in safe increments across the cell monitor inputs.  Applying the programming voltage is simpler if a board test fixture or device programming fixture provides simulated cell input voltages that meet the device limits.

    There is not presently a separate document on EEPROM programming for this part.

  • 0 in reply to WM5295
    TI__Guru 54715 points

    There is actually a hole in the above concept. The programming voltage is derived from the CPOUT voltage.  If your battery or pack voltage is in a range where the charge pump will run but not high enough for CPOUT to be >14V and the regulator load is heavy enough to turn on the charge pump, VGOOD will not be set and the programming will fail.  The part runs from the higher of the BATT or PACK pin. The voltage range of concern would be approximately 22 to 30V.

    An example might be a 7 cell board powered in test with a simulated 3.6V per cell or 25.2V on the battery side. The board has a load which causes the bq77PL900 charge pump to run.  The user then turns off the FETs and applies 20V to the pack to program the EEPROM.  The device runs from the higher voltage or 25.2, the CPOUT voltage is ~12.5V and VGOOD is not set when programming is attempted.  One solution would be to reduce the simulated battery voltage to ~ 20V.  The charge pump would turn off and the VGOOD would set.  Another solution would be to raise the applied PACK voltage to >30 but less than max. The charge pump would remain on but CPOUT would be above the minimum to produce VGOOD.