BQ25700A: Pin Voltage of CELL_BATPRESZ for 7.5V of battery voltage

Junghwa Ha

Prodigy 245 points

Part Number: BQ25700A

Hi,

If I want to set 7.5V of battery charging voltage, what voltage level of Pin CELL_BATPRESZ need to be set?

When I check DS, it shows typical 4 value as below.

But it is not linear when I compared Pin Voltage vs. battery voltage.

	Table1. Battery Cell Configuration
CELL COUNT	PIN VOLTAGE w.r.t.VDDA	BATTERY VOLTAGE (REG0x15)	SYSOVP
4S	75%	16.800V	19.5V
3S	55%	12.592V	18.5V
2S	40%	8.400V	12V
1S	25%	4.192V	5V

Junghwa

over 6 years ago

0 Wang5577 over 6 years ago

TI__Guru 56650 points

If the charging voltage is 7.5V, CELL_BATPRESZ pin should set as 2S setting to give a correct SYSOVP threshold for 7.5V battery voltage.

SYSOVP voltage has to be higher than the battery voltage. 1S is not good. 3S, 4S SYSOVP is too high and not necessary for a 7.5V battery.

0 Junghwa Ha over 6 years ago in reply to Wang5577

Prodigy 245 points

Hi,
According to your reply, CELL_BATPRESZ Pin just can be set to 2S ( 40% of VDDA) for 7.5V of battery with REG0x15 being set to 7.5V . I may not need to set pin voltage to be complied to exact 7.5V.
Let me make sure if I understand correctly.

0 Wang5577 over 6 years ago in reply to Junghwa Ha

TI__Guru 56650 points

2S CELL_BATPRESZ Pin setting not only sets the default charging voltage to 8.4V; but also sets the 12.5V SYSOVP. It you do 1S CELL_BATPRESZ Pin setting, 7.5Vbat could triggers the SYSOVP.

0 Junghwa Ha over 6 years ago in reply to Wang5577

Prodigy 245 points

Yes. I know it set SYSOVP level,too. My point is not that one. I want to know if I can set exact charging voltage level by CELL_BATPRESZ Pin voltage setting. According to your explanation, we just have 1 to 4 Cell selection through this pin and exact charging voltage level needs to be set through REG0x15.

0 Wang5577 over 6 years ago in reply to Junghwa Ha

TI__Guru 56650 points

CELL_BATPRESZ Pin only can set one default charging voltage for each cell selection.

To get exact charging voltage level, it needs to be set through REG0x15.

0 Junghwa Ha over 6 years ago in reply to Wang5577

Prodigy 245 points

Thank you.

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BQ25700A: Pin Voltage of CELL_BATPRESZ for 7.5V of battery voltage