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BQ77905: I have questions about BQ77905

Jae Cheong Jeong
Intellectual 260 points
Part Number: BQ77905
Other Parts Discussed in Thread: BQ77904

Hello I'm Jae Cheon.

I hope to make BMS circuit that have function which provide safety protection on overvoltage, undervoltage, overdischarge, and overcharge.

So I was searching IC, and I found BQ77905.

I read document about BQ77905 But I want to certainly know information about BQ77905 through question and answer.

1. if I use the BQ77905, can I make a BMS circuit which have that function?

2. I hope to make BMS circuit that can use it to 15V/100Ah Li-ion battery system. Should I connect BQ77905 and battery as picture below?

3. if can BQ77905 is used to LiFePO4 battery?

thanks.

  • 0
    TI__Guru 54715 points
    Hi Jae,
    1. The bq77905 has overvoltage, undervoltage, and discharge overcurrent protection. It does not have a charge overcurrent protection. If you have a MCU in the pack which is measuring current or getting current from a gauge, the MCU could command the charge FET off using the CTRC input when an overcurrent charge condition was detected.
    2. The cells can connect in parallel for higher capacity. When connecting to the bq77904 the bottom of the bottom cell would connect to VSS and VC1 is the lowest cell input. See figure 27 on page 32 of the data sheet.
    3. The bq77905 can support the voltages for LiFePO4 cells as shown in table 3 of the data sheet, but no configurations have been defined as of this date which are suitable for these lower voltage cells (tables 1 & 2). If the part will meet your needs please contact your local TI representative to determine if the volume and need date support definition of a configuration for your thresholds.