BQ24780S: no discharging current

Chong Yu

Part Number: BQ24780S

Hi,

My customer need assistance.

BQ24780s in my application is able to do charging normally.
While discharging, SYS is with normal voltage, but without any current.

Please help. Thanks.

over 4 years ago

0 Pengzhao Zhu over 4 years ago

TI__Genius 11385 points

Hi Chong,

BQ24780S does not have any way to stop battery from discharging. Current can always conduct through the body diode of the BATFET even if the BATFET is turned off.

I would recommend double checking the setup.

Thanks and I hope this helps,

Peng

*Please press "This Resolved My Issue" on the thread if my answer is satisfactory

0 ding mh over 3 years ago

Prodigy 31 points

当我拔掉适配器，放电控制都是由硬件自己切换的吗？不需要软件配置的参与，除了配置放电电流外。是这样吗？

0 Pengzhao Zhu over 3 years ago in reply to ding mh

TI__Genius 11385 points

Hi,

No, what I mean is that the charger has no way to controlling discharge current so it does not make sense to look at the charger to debug your described discharge current issue.

Even when the BATFET is off, the discharge current will conduct through the body diode of the MOSFET.

I would recommend double checking the setup.

Thanks and I hope this helps,

Peng

*Please press "This Resolved My Issue" on the thread if my answer is satisfactory

0 ding mh over 3 years ago

Prodigy 31 points

你好，那放电电流是怎么控制的呢？是根据负载自己确定的吗？那配置的放电电流寄存器是有什么用呢？

0 ding mh over 3 years ago

Prodigy 31 points

现在软件的配置如下：

充电控制寄存器 0 0x12 0x8100

充电控制寄存器 1 0x3b 0xC210

充电控制寄存器 2 0x38 0x0304

充电控制寄存器 3 0x37 0x1A40

充电电流 0x14 0x0800

充电电流 0x15 0x22c4

充电输入电流 0x3f 0x1000

放电电流 0x39 0x0bb8

软件现在这个配置能正常充电，但是拔掉适配器，不能放电，没有放电电流，但是有放电电压。

0 Pengzhao Zhu over 3 years ago in reply to ding mh

TI__Genius 11385 points

Hi Ding,

Yes, discharging current is determined by load. With no adaptor and battery discharging through the MOSFET, the model is similar to a forward biased diode (parasitic body diode of MOSFET) to the system load.

The DischargeCurrent() register is only applied when the power stage is active in hybrid boost mode but not in direct battery discharge.

More information is available on the following thread.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/764931/bq24780s-learn-function-with-discharge-current-regulation

Thanks and I hope this helps,

Peng

*Please press "This Resolved My Issue" on the thread if my answer is satisfactory

0 Chong Yu over 3 years ago in reply to Pengzhao Zhu

TI__Intellectual 1435 points

Hi, Pengzhao

My customer replied:

Hello, is there basic register software configuration for charge and discharge? I want to first eliminate the software problem, this problem has been plagued for a long time. Please provide the software register configuration.

0 Pengzhao Zhu over 3 years ago in reply to Chong Yu

TI__Genius 11385 points

Hi Chong,

Unfortunately, we don't have written example software because it varies by application. However, we have the EVM that they can use to reference and compare their test results with.

https://www.ti.com/tool/BQ24780SEVM-583

Thanks and I hope this helps,

Peng

*Please press "This Resolved My Issue" on the thread if my answer is satisfactory

0 Chong Yu over 3 years ago in reply to Pengzhao Zhu

TI__Intellectual 1435 points

Hi, Pengzhao

My customer replied:

Hello, in the screenshot I took, the pins of IAP IDCHG pmon are useless, is it ok to design this way?

0 Pengzhao Zhu over 3 years ago in reply to Chong Yu

TI__Genius 11385 points

Hi Chong,

Yes, it is ok to design like this. You can also float the pins.

Thanks and I hope this helps,

Peng

*Please press "This Resolved My Issue" on the thread if my answer is satisfactory

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BQ24780S: no discharging current