BQ25792EVM: When VBUS is 9V, IBAT has around 1mA discharging current

Hello,

I am having trouble understanding the problem. The battery only quiescent current seems fine.

If you have a 8.1 V battery with 8.4 V regulation you should be charging. Can you recapture the registers? I found some errors, for example the ADC is not enabled yet I see register settings. Please take it at the time of issue. Also, can you see what happens when you remove the ammeter in series?

Regards,

Mike Emanuel

Hi Mike:

Michael Emanuel35 said:

Please take it at the time of issue. Also, can you see what happens when you remove the ammeter in series

Please refer below figure and the register parameters load when issue happened, and whatever we connect ammeter or not, which has the same result.

It's my fault I need to re-describe this issue, but I forgot the real battery voltage.

At that moment I saw the charging current from 400mA then step by step down to 0 mA, we make sure that should be in termination status.

Then we plug out VBUS first, then disconnect Battery from EVM, and series ammeter then re connect battery on EVM.

When connected battery at this moment we saw the bat Iq is around 20uA, and we didn't modify any register setting.

Then we plug in VBUST again, and we saw the bat Iq is around 1mA (discharging to BQ25792), at this moment we didn't do any register setting just default.

We need to know does there has any register function can decrease this 1mA?

Looking forward your feedback.

Thanks a lot.

* Created: Thu Sep 07 15:29:49 CST 2023
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_2_00-bq25790_92.bqz
*
REG00	00	12
REG01	01	348
REG03	03	C8
REG05	05	2B
REG06	06	8D
REG08	08	C3
REG09	09	05
REG0A	0A	63
REG0B	0B	DC
REG0D	0D	4B
REG0E	0E	3D
REG0F	0F	A2
REG10	10	85
REG11	11	00
REG12	12	00
REG13	13	41
REG14	14	16
REG15	15	EA
REG16	16	C0
REG17	17	7A
REG18	18	54
REG19	19	8D
REG1B	1B	0F
REG1C	1C	0A
REG1D	1D	01
REG1E	1E	40
REG1F	1F	00
REG20	20	00
REG21	21	00
REG22	22	A0
REG23	23	80
REG24	24	00
REG25	25	00
REG26	26	20
REG27	27	00
REG28	28	00
REG29	29	00
REG2A	2A	00
REG2B	2B	00
REG2C	2C	00
REG2D	2D	00
REG2E	2E	30
REG2F	2F	00
REG30	30	00
REG31	31	09
REG33	33	00
REG35	35	23CE
REG37	37	23D2
REG37	39	227E
REG3B	3B	1EA1
REG3D	3D	1E42
REG3F	3F	262
REG41	41	26
REG43	43	15
REG45	45	1E
REG47	47	00
REG48	48	08

Hi Mike:

Michael Emanuel35 said:

Can you send a schematic, I need to see how your charger is configured?

Yes, you checked before, but it's ok, because we are testing EVM, this issue is not on my PCBA.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1268321/bq25792-schematic-check-request

Michael Emanuel35 said:

Do you have a system load? If not, EN_HIZ. I was able to achieve 100 uA discharge from the battery.

No, we are just testing EVM, likes the photo, we do not connect system load, but in our application scenarios we will connect system load. 

Michael Emanuel35 said:

Consider using the ShipFET to shut off quiescent current draw from the charger when the battery is fully charged.

I guess, if turn off shipFET, that device will enter shutdown mode, then system load will not have power from VBUS.

Am I right? if yes, we cannot accept this result.

Beacause our application scenarios just have a concern after charging terminated and didn't plug out VBUS all night, but on this scenarios the device cannot see 100% soc because there has 1mA discharging current from battery to battery charger.

Except turn off shipFET, do you have other recommendations for us?

Looking forward your feedback.

Thanks a lot. 

Hello Mike:

Understood your tested results.

Please refer our charger request spec as below.

VIN: 5V/9V, VOUT: 8.4V/2.5A(charging), we need the battery Iq should be 0 when charged terminated.

Would you please recommend a new charger IC for us?

Looking forward your feedback.

Thanks a lot.

Hello Mike:

Sorry I cannot explain well, but our customer told me which liked your iphone charging all night, but SOC was 99%. can you accept this result?

I think that customer just wants low Iq when charging terminated.

When charging terminated that BATFET should be turned off, am I right?

If I'm right, why there has 450uA leakage current?

Is it from internal feedback trace or some compensation circuit?

Whatever, they can accept max77963 spec.

Do you have recommend part number to replace it?

Looking forward your feedback.

Thanks a lot.

https://www.analog.com/media/en/technical-documentation/data-sheets/max77963.pdf