BQ25756: BQ25756 VAC_DPM_STAT

Shuichi Hashimoto

Prodigy 40 points

Part Number: BQ25756

Tool/software:

Dear Support.

I am using a BQ25756.

Charging does not start despite Power Good and CE='L'.

At that time, VAC_DPM_STAT=1.

What is the status of this?

The Power Good range is 40~60V, and charging does not start when the input voltage is 42V or lower.

What could be the problem?

Can you please help me?

Thank you in advance.

over 1 year ago

0 Ethan Galloway over 1 year ago

TI__Mastermind 31305 points

Hello Shuichi,

Thanks for working with this. Can you answer a few questions about this to help us debug?

What all settings have you changed on the EVM?

What's your input/output voltage?

What type power supplies/electronic loads do you have on your input/output?

Best Regards,
Ethan Galloway

0 Shuichi Hashimoto over 1 year ago in reply to Ethan Galloway

Prodigy 40 points

Dear Ethan.

Thank you for your response.

I will answer your questions.

>What all settings have you changed on the EVM?

Although it is not EVM that we are using, we are not configuring the BQ25756 with I2C.

The input and output currents are limited by external resistors.

Input:5A

Output:7.5A

External resistors are calculated using BQ25756-DESIGN-CALC.

>What's your input/output voltage?

Input:40~60V

Output:25.2V

External resistors are calculated using BQ25756-DESIGN-CALC.

>What type power supplies/electronic loads do you have on your input/output?

Input: Regulated Power Supply 200~400W

Output: No load,Electronic load or LiPo battery

At no load, the output will hover around 25.2V for 42~60V, but 1.5V for 40V.

When LiPo battery, charging starts at 42~60V, but not at 40~41V.

Is there a problem with the above settings?

Thank you in advance.

0 Ethan Galloway over 1 year ago in reply to Shuichi Hashimoto

TI__Mastermind 31305 points

Hello Shuichi,

Thanks for the new information and thanks for being patient with this. I'll get back to you later this week.

Best Regards,
Ethan Galloway

0 Ethan Galloway over 1 year ago in reply to Ethan Galloway

TI__Mastermind 31305 points

Hello Shuichi,

You might want to set the ACUV/ACOV power good range to be slightly wider than your input supply. Will this work for your application?

Best Regards,
Ethan Galloway

0 Shuichi Hashimoto over 1 year ago in reply to Ethan Galloway

Prodigy 40 points

Dear Ethan.

Thank you for your response.

The ACUV/ACOV setting values are wide.

The resistance values are as follows.
Do they need to be wider?

RAC1=1000kohm
RAC2=10kohm
RAC3=20kohm

Voltage range in BQ25756-DESIGN-CALC
37.8V - 61.8V

Please confirm.

Thank you in advance.

0 Ethan Galloway over 1 year ago in reply to Shuichi Hashimoto

TI__Mastermind 31305 points

Dear Shuichi,

Yes, I would recommend setting the ACUV setting slightly lower.

The slightly wider settings will account for the variation in resistance from the manufacturing tolerances.

Best Regards,
Ethan Galloway

0 Shuichi Hashimoto over 1 year ago in reply to Ethan Galloway

Prodigy 40 points

Dear Ethan.

Thank you for your response.

I will try to change the resistance value.

Why doesn't charging start even though the Power Good signal is enabled?

Is there any relationship between ACUV/ACOV and the Power Good signal?

Thank you in advance.

0 Ethan Galloway over 1 year ago in reply to Shuichi Hashimoto

TI__Mastermind 31305 points

Hello Shuichi,

The charger reads that it's in VAC_DPM. In this mode, the charger will limit the charge current to prevent the voltage from falling past the VAC_DPM limit. When you took the screenshot, do you know what the charge current was?

Best Regards,
Ethan Galloway

0 Shuichi Hashimoto over 1 year ago in reply to Ethan Galloway

Prodigy 40 points

Dear Ethan.

Thank you for your response.

No load when screenshots are taken.

The current is 0A.

Power is turned on with CE='L'.

Thank you in advance.

0 Ethan Galloway over 1 year ago in reply to Shuichi Hashimoto

TI__Mastermind 31305 points

Hello Shuichi,

Because the charger is VAC_DPM, the charger is regulating the VAC voltage to fall past the ACUV. I think charge current is 0 in this case to be sure the VAC voltage doesn't fall any lower.

Let me know if you have any other questions.

Best Regards,
Ethan Galloway

Power management

Power management forum

BQ25756: BQ25756 VAC_DPM_STAT