BQ24105-Q1: recharge threshold

Dear Koji,

VRCH is the value the battery voltage must dip below the regulation voltage in order to start recharging.  This is called the recharge threshold in the datasheet. However, the point recharge will start is VOREG-VRCH.

Thanks,

Mike Emanuel

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Hi Mike-san

Thank you for response.

>However, the point recharge will start is VOREG-VRCH.

I don't understand the above comment.

I think that VOREG-VRCH is a large voltage with respect to VRCH.

Please give a detailed explanation.

Best Regards,

Koji Hayashi

Koji-san,

VRCH is 100 mV per cell. If you had a one cell application with regulation at 4.2 V, the threshold to restart charge is 4.2 V minus 100 mV or 4.1 V.

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.

Hi Mike-san

Thank you for response.

Allow me to confirm this.

>2. If the part dips below the recharge threshold, the charger will return to the start of the flow.

Is it VRCH or VOREG-VRCH where the charger returns to the beginning of the flow ?

It will be 0.1V for VRCH and 4.1V for VOREG-VRCH.

Best Regards,

Koji Hayashi

Koji-san,

It will attempt to start charging again when the battery voltage drops below VOREG-VRCH or 4.1 V.

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.

Hi Mike-san

Thank you for response.

>It will attempt to start charging again when the battery voltage drops below VOREG-VRCH or 4.1 V.

Does this mean returning to the beginning of FLOW ?

If this is correct, isn't the following "the recharge threshold" VOREG-VRCH ?

>2. If the part dips below the recharge threshold, the charger will return to the start of the flow.

Best Regards,

Koji Hayashi

Koji-san,

As shown in the bottom of the flow, when VBAT>VRCH, charge is complete and the charger stays in the flow there. When VBAT<VRCH, Battery Absent is indicated and the part returns to the beginning of the flow. As stated earlier, what is meant by dipping below VRCH is dropping a value of 100 mV/cell below the regulation voltage of the battery. Again, for a one-cell lithium-ion application with 4.2 V regulation, this would be 4.1 V.

If you look at the electrical characteristics on page 4 of the datasheet, you will see the VRCH is specified as "Below VOREG." The part will not wait to restart charge below 100 mV as this is very deep into the Battery Short condition, which is lower than 2 V per cell.

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.

Hi Mike-san

Thank you for response.

I'm sorry I didn't understand.

Does it recharge when it gets below 4.1V mean that it doesn't go back to the beginning of the OPERATIONAL FLOW CHART ?

If correct, where in the OPERATIONAL FLOW CHART is this going ?

Best Regards,

Koji Hayashi

Hi Mike-san

>The last decision block in the Operational Flow Chart checks to see if VBAT<VRCH (in this case VBAT< 4.1 V).

From your previous answer VOREG = 4.2V, VRCH = 0.1V.

VOREG-VRCH = 4.1V

When VBAT becomes less than 4.1V, it returns to the beginning of FLOW.

Is this understanding correct ?

Best Regards,

Koji Hayashi

Koji-san,

Yes that is correct.

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.