BQ24715: What is the correspondence between the Vout and Vin of the BQ24715 in different Cell settings?

Chen Bogey8

Mastermind 9990 points

Part Number: BQ24715
Other Parts Discussed in Thread: BQ24157

Hi Sir

The measure waveform, may we check as below questions with you?

The questions as below:

What is the correspondence between the Vout and Vin of the BQ24715 in different Cell settings?

2. Suppose that in the case of 3Cell, if each Cell is fully charged at 4.2V, does Vin need a higher value than the output (Ex: 12.6V)?? How much voltage does Vin need to output higher than?

How much voltage should I add if needed? Is there a relationship??

Bogey

BQ24175.docx

over 5 years ago

0 Jeff F over 5 years ago

TI__Guru**** 165786 points

Chen,

Are you referring to BQ24157 or BQ24715? There is no BQ24175.

Regards,

Jeff

0 Chen Bogey8 over 5 years ago in reply to Jeff F

Mastermind 9990 points

Hi Jeff

Sorry, it is BQ24715.(add circuit)

And Customer want use in Vin=15V.

0508.BQ24175.docx

0 Joel Hernandez II over 5 years ago in reply to Chen Bogey8

TI__Mastermind 25800 points

Hey Chen,

Please refer to the VCC to SRN COMPARATOR (VCC_SRN), SLEEP section of the EC table in the datasheet.

Regardless of the setting on the CELL pin, the VCC-SRN voltage must be above the VVCC-SRN_RHYS value. The CELL pin only dictates what the maximum and default charging regulation voltages will be set to. The converter will monitor the VCC-SRN voltage to enable or disable charging. The rising threshold can be 675mV above SRN. Because of the diode drop to VCC, VIN would need to be at least 675mV + Vf + VSRN.

Regards,

Joel H

0 JimmyChang73 over 5 years ago in reply to Joel Hernandez II

Prodigy 80 points

Hi Joel H,

According to your explanation, VCCIN_Min shall at least more than the summation of 675mV+VF(series diode of VCC)+VSRN.

How to select the apposite value of VSRN for above-mentioned calculation? Or if battery pack is not present, too?

Could you give me a example to decide VCCIN_Min with 3 series battery cell condition and VF=375mV?

Thanks,

JImmy C

0 Joel Hernandez II over 5 years ago in reply to JimmyChang73

TI__Mastermind 25800 points

Hey Jimmy,

VSRN is the maximum battery voltage. It should be equal to the max charge regulation voltage set by you.

For a 3S battery, what is your maximum charging regulation voltage for each cell? 4.2V? 4.4V? From there, you must make sure the VCCIN_Min is > 3Cells x MaxChargeVoltage/cell + 375mV (Vf) + 675mV (Vsleep).

Regards,

Joel H

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BQ24715: What is the correspondence between the Vout and Vin of the BQ24715 in different Cell settings?