BQ25896: Won't allow above 50-60mA

Renan Santos Adriano

Part Number: BQ25896

Hello Team,

My Customer is using BQ25896 in a 5V charger capable of giving more than 500mA (actually 2A) of current to charge a 18650 Li-ion battery. The charging current does not increase above 50-60mA. They have verified the charger capability but it simply charges the battery too slowly, what might be done to improve this?
The charger is in Fast charge mode, the Charge voltage and current registers are default values at 4.2V and 2048mA respectively.

Just wanted to clarify, that they have followed the instruction provided in BQ2589X EVM board guide and disabled ICO as well. The chip simply won't allow more than 60mA current to charge the battery.

Regards,

Renan

over 3 years ago

0 Ning T over 3 years ago

TI__Mastermind 46651 points

Renan,

Please visit https://e2e.ti.com/support/power-management/f/196/t/874557 for BQ2589X: Schematic Review and PCB Layout Design Tips and https://e2e.ti.com/support/power-management/f/196/t/875386 for BQ2589x/BQ25898x FAQs. FAQ#3 should be helpful to your questions.

Please check if the input source is over-loaded, either the current exceeds the input current limit or the VBUS pin voltage falls below the input voltage limit. When the input current limit or input voltage limit is reached, the device then reduces the charge current until the input current falls below the input current limit and the input voltage rises above the input voltage limit. Please refer to 9.2.6.2 Dynamic Power Management on the d/s and Extract maximum power from the supply when charging a battery (http://www.ti.com/lit/an/slyt569/slyt569.pdf) for the details.

Thanks,

Ning.

0 Renan Santos Adriano over 3 years ago in reply to Ning T

TI__Genius 16540 points

Hello Ning,

Got feedback from our customer that, the diagnosis that charge current is being limited by the input current limit is true. The problem that they face is that, without reducing the charge limit to 200-300mA in the 0x00 register, the VBUS stays at 3.2V on Vsys ( in absence of battery and despite default Vsysmin=3.5v). If the system is powered up with a battery , the battery does not get charged (they see voltage reducing over time) although the STAT pin goes LOW to indicate charging, and the device register 0x0B(reads 0x57) also indicates fast charging. This situation changes as soon as they set register 0x00 to 100mA input current limit. Then Vsys increases to 3.7v and battery starts charging at 50mA current. Kindly suggest what maybe going wrong.

Regards,

Renan

0 Ning T over 3 years ago in reply to Renan Santos Adriano

TI__Mastermind 46651 points

Renan,

Could you please provide the followings when the device works normally and abnormally respectively?

The test conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS.
All the register settings

Thanks,

Ning.

0 Ning T over 3 years ago in reply to Ning T

TI__Mastermind 46651 points

Hi,

We have not heard back from you for a while. The thread is considered solved and closed.

Thanks,

Ning.

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BQ25896: Won't allow above 50-60mA