BQ25618E: ON/OFF is repeated during charging

Kaji@PAN

Part Number: BQ25618E

Hello,

I am an FAE for a distributor that handles TI products.
A colleague of mine asked a question in the thread below.
And since I took over the case, I will continue to ask questions in this thread.
In the thread below, my customer confirmed whether changing REG01[3:1] to 111 or 000 changed the behavior.
The result is below.

REG01[3:1] to 111
When the battery voltage is around 3.8V, the charging current repeats ON/OFF periodically.
REG01[3:1] to 000
When the battery voltage is around 2.7V, the charging current repeats ON/OFF periodically.
REG01[3:1] to 101
When the battery voltage is around 3.6V, the charging current repeats ON/OFF periodically.

It seems to have something to do with the SYS_MIN setting.
Is there a way to eliminate the change in charging current?

Best regards,

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1216423/bq25618e-on-off-is-repeated-in-the-middle-of-charging

over 1 year ago

0 Ning T over 1 year ago

TI__Guru 52991 points

Hi,

Will check and get back to you.

Thanks,

Ning.

0 Kaji@PAN over 1 year ago in reply to Ning T

Mastermind 7360 points

It's been a few days, but is it still possible to answer?
I had an additional question from the customer.
In BQ25618EVM, SYS output waveform is measured without I2C setting and battery connection.
Then SYS output stops when VIN(VBUS) is less than 4.5V.
Same with or without load on SYS.
Isn't VBUS able to output to SYS from 4V to 13.5V?
Best regards,

0 Ning T over 1 year ago in reply to Kaji@PAN

TI__Guru 52991 points

Hi,

Before VBAT reaches VSYSMIN, BATFET is working in LDO mode; after VBAT reaches VSYSMIN, BATEFT will be working in fully on mode. So there is BATFET transitioning between LDO mode and fully on mode around VSYSMIN. Please refer to the e2e below for more information.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/933431/bq25606-pulsed-ichg

Thanks,

Ning.

0 Kaji@PAN over 1 year ago in reply to Ning T

Mastermind 7360 points

Thank you for your reply.
I confirmed the contents of the past E2E.
It is recommended to connect 10uF to the BAT pin, but should I increase the capacity of this capacitor?
Is there an upper limit for capacitor capacity?
Also, can you comment on the additional question about the SYS output stopping when 4.5V is applied to VBUS?
Best regards,

0 Ning T over 1 year ago in reply to Kaji@PAN

TI__Guru 52991 points

Hi,

1. The battery itself is high-capacity capacitor. Small capacitance increase on the BAT pin is hard to help.

2. The charger is basically a step-down DC-DC (buck) converter. It requires the input voltage to be higher than the output voltage with some headroom for normal operations. The device may enter sleep mode or HIZ mode under certain conditions. Please refer to 8.4 Device Functional Modes on the d/s for the details.

Thanks,

Ning.

0 Kaji@PAN over 1 year ago in reply to Ning T

Mastermind 7360 points

Thank you for your reply.
I understand answer 1.
Regarding answer 2, I will change the question.
In what mode will this device work if the battery is not connected?
Best regards,

+1 Garrett Kreger over 1 year ago in reply to Kaji@PAN

TI__Mastermind 26860 points

Hi,

Please see my comments below in regards to 2)

Kaji@PAN said:
In BQ25618EVM, SYS output waveform is measured without I2C setting and battery connection.
Then SYS output stops when VIN(VBUS) is less than 4.5V.

The SYS output likely stops in your test because VBUS dropped below the VINDPM threshold. The threshold is default set to 4.5V. If you use I2C register settings to lower the threshold to minimum value of 3.9V then you can operate the device down the the minimum allowable VBUS input of 4V.

Kaji@PAN said:
In what mode will this device work if the battery is not connected?

With battery not connected the device will regulate SYS pin voltage approximately 180 mV above the VSYS min setting (default 3.5V). Please see the FAQ I have linked below for additional information on device operation when no battery is connected.

FAQ: Why does the led connected to stat pin flashes and the sys voltage unstable when battery is not connected?

Best Regards,

Garrett

Power management

Power management forum

BQ25618E: ON/OFF is repeated during charging