LP3923: How to close the charge function?

user5095810

Part Number: LP3923
Other Parts Discussed in Thread: BQ25892,

Hi Sir

I have designed a power system which based on the LP3923 and BQ25892. Thus, the charge function which integrated at LP3923 has problem. I have no idea of how to use the 'BAT' pin at LP3923. For now, I connect this pin to Vsystem which connected to the SW pin of BQ25892.

How can I do to close the charge function of LP3923? and is there anything wrong with the connection of 'BAT' to 'Vsystem'?

Look forward to your favourable reply.

over 6 years ago

0 Frank Dehmelt over 6 years ago

TI__Genius 9615 points

Hello,
I presume that you can only quit charging via an I2C command to register 8h'10 (FORCE_EOC), but this would only stop charging and not prevent charging in the first place. I'm looping in the expert for this device, but due to Thanksgiving in the US, please expect some delay.
Best regards,
Frank

0 user5095810 over 6 years ago in reply to Frank Dehmelt

Prodigy 80 points

Hi Frank
Thanks for your reply, and How about the design of PMU and Charge IC ? For Now, I connect the 'VBAT' pin of PMU to 'Vsystem' pin of charge IC.
Is there anything wrong with it ?

BR
Thanks

0 Richard Solarski over 6 years ago in reply to user5095810

TI__Genius 10885 points

Hi BR,

I would expect this to be OK, the device cannot charge if CHG_IN is not present.

Best Regards,
Rick S.

0 user5095810 over 6 years ago in reply to Richard Solarski

Prodigy 80 points

Power system.docx

0 user5095810 over 6 years ago in reply to Richard Solarski

Prodigy 80 points

Maybe I do not describe this issue fully. I have attached the file to explain in detail. Pls give more advise to this design. Thanks a lot.

0 Richard Solarski over 6 years ago in reply to user5095810

TI__Genius 10885 points

It is generally not recommended to have two regulators operating in parallel. Since CHG_IN is not required to enable the PMIC, you should be able to float CHG_IN while connecting HF_PWR to VSYS. This should achieve a similar result without the risk of parallel regulators.

Best Regards,
Rick S.

0 user5095810 over 6 years ago in reply to Richard Solarski

Prodigy 80 points

Hi Sir

I think it is not appropriate that the HP_PWR to VSYS can solve my problem. VSYS will be set to high when the battary is on or the usb is charged. and it will give the power on signal. the phone will be powerd automatic.

can you give me more advise?

Thanks

0 user5095810 over 6 years ago in reply to user5095810

Prodigy 80 points

In addition, I need use the GHG_IN PIN on LP3923 to detect the charger is plugged in or pulled out,and I want to trigger the mobile phone power on through this pin.

0 Richard Solarski over 6 years ago in reply to user5095810

TI__Genius 10885 points

The LP3923 can use three different inputs to initiate a power-up sequence : PWR_ON, CHG_IN, or HF_PWR. Afterwards only PS_HOLD needs to be present to stay active. Connecting HF_PWR to USB_VBUS will have the same effect as connecting CHG_IN to USB_VBUS.

By leaving CHG_IN disconnected, there are less scenarios where this redundant charger could interfere with normal operation.

Best Regards,

Rick S.

Power management

Power management forum

LP3923: How to close the charge function?