BQ25638: Charging efficiency standard estimation

eajon chen

Part Number: BQ25638
Other Parts Discussed in Thread: BQ27Z746

Tool/software:

Hi TI team

We use inductance DCR type: 18mΩ5, max 22mΩ, adding the impedance of the line, the total impedance is expected to be 25mΩ，the current test charging efficiency is as follows:

We want to evaluate the charging efficiency standards of vbat voltage 3.3V, charging current 4.2A, VBAT 3.8V, charging current 3.75A, and VBAT 4.2V charging current 3.4A. How do calculate this。tks！

11 months ago

0 Ning T 11 months ago

TI__Guru 57781 points

Hi,

It's hard to calculate the efficiency. It's much easier and quicker to measure the efficiency on the EVM.

Thanks,

Ning.

0 eajon chen 11 months ago in reply to Ning T

Prodigy 145 points

Hi Ning

At present, our product test charging efficiency is 1% lower than EVM。If we cannot calculate the charging efficiency standard, it is difficult for us to judge that our charging efficiency is qualified.

0 Ning T 11 months ago in reply to eajon chen

TI__Guru 57781 points

Hi,

We will get back to you next week.

Thanks,

Ning

0 Ning T 11 months ago in reply to Ning T

TI__Guru 57781 points

Hi,

You mentioned "product test charging efficiency is 1% lower than EVM". But the datasheet does not show the efficiency data under the same test conditions as you did. Did you test both your board and the EVM under the same test conditions?

Thanks,

Ning.

0 eajon chen 11 months ago in reply to Ning T

Prodigy 145 points

BQ25638EVM
3.1	Input VBUS = 5V+/- 3% Ripple voltage < 100mV	5.04V
3.1	Input current (A)	3.034A
3.1	Battery Charge Current (A)	4.178A
3.1	VSYS	3.363V
3.1	VBAT	3.318V
3.1	Charger efficiency > 93%		90.66%
3.6	Input VBUS = 5V+/- 3% Ripple voltage < 100mV	5.04V
3.6	Input current (A)	3.040A
3.6	Battery Charge Current (A)	3.796A
3.6	VSYS	3.748V
3.6	VBAT	3.707V
3.6	Charger efficiency > 93%		91.84%
4.2	Input VBUS = 5V+/- 3% Ripple voltage < 100mV	5.01V
4.2	Input current (A)	3.073A
4.2	Battery Charge Current (A)	3.41A
4.2	VSYS	4.271V
4.2	VBAT	4.233V
4.2	Charger efficiency > 93%		93.76%

We have tested EVM, and the test data of EVM is as above。

0 Ning T 11 months ago in reply to eajon chen

TI__Guru 57781 points

Hi,

Was the same efficiency test methodology used when testing the custom board and the EVM?

Thanks,

Ning.

0 eajon chen 11 months ago in reply to Ning T

Prodigy 145 points

Hi Ning

Yes, we use the same method to test efficiency for PCM and EVM。

TKS!

0 Ning T 11 months ago in reply to eajon chen

TI__Guru 57781 points

Hi,

What are the dimensions of the custom charger circuitry only? Are there other circuitry on the same PCB?

Thanks,

Ning.

0 eajon chen 11 months ago in reply to Ning T

Prodigy 145 points

Hi Ning

Our PCB dimensions is 70*11.5mm，In addition to the charging circuit, there is also the circuit of BQ27Z746。

TKS!

0 Ning T 11 months ago in reply to eajon chen

TI__Guru 57781 points

Hi,

Did you compare the IC temperature for your board and the EVM? Higher power density may decrease the efficiency.

Thanks,

Ning.

0 eajon chen 11 months ago in reply to Ning T

Prodigy 145 points

Hi Ning

Our PCB temperature high than zhe EVM.

TKS!

+1 Ning T 11 months ago in reply to eajon chen

TI__Guru 57781 points

Hi,

The resistance on the charging path usually get higher when the temperature is hotter. So the efficiency usually decreases as the temperature rises.

Thanks,

Ning.

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BQ25638: Charging efficiency standard estimation