BQ2970: What is the maximum charge current and discharge current of BQ2970 IC series?

saiteja manchukanti

Part Number: BQ2970
Other Parts Discussed in Thread: BQ2980

I am using "BQ29700DSER" IC for 2 cell Li-Ion battery protection. According to datasheet, over discharge current threshold is 0.1 V and over charge current threshold is -0.1 V.

I would like to understand these voltage thresholds in terms of currents. Please explain how to understand max charge current and discharge current supported by the IC.

I am attaching the datasheet for your reference.

http://www.ti.com/lit/ds/symlink/bq2970.pdf

Let me know if I am not clear and please help me in this regard.

Thanks.

over 7 years ago

0 Onyx Ahiakwo over 7 years ago

TI__Guru* 76230 points

Hi Saiteja
The device uses the voltage drop accross the fets and the Rdson of the fet to determine the current. So essentially your choice of fets will determine the current thresholds.
thanks
Onyx

0 saiteja manchukanti over 7 years ago in reply to Onyx Ahiakwo

Intellectual 330 points

Hi Onyx,
Thanks for your response.
For "BQ29700DSER" IC, values of over discharge current threshold(0.1V) and over charge current threshold(-0.1V) are same. According to above theory, maximum charging current and maximum discharge current will be same.
Can't I design the protection circuit having different max charging current limit and max discharge current limit with "BQ29700DSER" IC ?

Awaiting your reply.

0 Onyx Ahiakwo over 7 years ago in reply to saiteja manchukanti

TI__Guru* 76230 points

Hi Saiteja,

you will have to choose a different flavour of the device then. See table below:

thanks

Onyx

0 saiteja manchukanti over 7 years ago in reply to Onyx Ahiakwo

Intellectual 330 points

Hi Oynx,

Thanks for your reply.

Generally Ron for FETs vary depending upon external factors like operating voltage, temperature. Can you please, Ron at which conditions is to be chosen?

0 Onyx Ahiakwo over 7 years ago in reply to saiteja manchukanti

TI__Guru* 76230 points

Hi Saiteja,

But there will be a max and min Rdson, right? You have to choose a good fet with a relative constant Rdson with little variation over temperature and then when doing your calculations give room for those variations due to temperature and gate voltages. If this doesn't work for you, i would recommend considering the bq2980 which uses a sense resistor instead of the voltage drop across the fets.
thanks
Onyx

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BQ2970: What is the maximum charge current and discharge current of BQ2970 IC series?