BQ24773: The I2C register review for the BQ24773

Hello Zhang,

Is this on a custom board or an EVM?

Best Regards,

Christian

Hi Christian,

This happened on customer board.  We didn`t have BQ24773 EVM.

BR

Cayden

Hello Cayden,

Can you provide your schematic?

Best Regards,

Christian.

Hi Christian,

I have send you schematic by email.

BR

Cayden

Hello Cayden,

On the other post, you mentioned that some of the register values are not being set correctly. I think this might be related to that issue. I going to try and replicate this on an EVM with your test parameter.

I have a few questions:

What is the battery voltage that is attached?

What is adapter voltage?

Is the system load 1A?

Charge voltage=0V?Charge current=0A?

Best Regards,

Christian

Hi Christian,

1. Battery voltage: Only adapter without battery when read the registers.

2. Adapter voltage: 19.5V;

3. Chatger voltage: Default value without any setting operation, and it can't be rewriten for our board achually;

4. Charger current: Default value without any setting operation and it can't be rewriten for our board actually, thanks.

Hello Zhang,

Zhang Liang said:

1. We connect both the system and battery, the output voltage will be cycle(11mS) drop more than 7V when the output current is 1A;

You mentioned this only happens when battery and system are connected. What is the battery voltage that is attached. What is the system load that is attached. I want to try and replicate this issue on the EVM.

Best Regards,

Christian.

Hi Christian,

Sorry for my error description, this drop voltage is happen when I only connect the adapter and system and remove the battery, and the output voltage is normal when we connect both adapter, battery to system, we consider if this charger's register is set to prioritize searching for batteries, and then it will be  provided the power by adapter when it can't find the battery, we don't know if our opinion is right or not?

The below is our current phenomenon:

1. Connect to Battery: Vout is normal, Vbat=12V, Vout=13.5V, the P-FET between bettery and system is not conduction, it can work normal when we connect battery and adapter to system;

2. Remove the battery: Vout will periodic voltage drop(11mS), and Vgs for the P-FET will rise and Vbat also rise;

3. Remove the battery: We connect Vbat to Vout, the Vout is normal;

4. The register read some empty data after we write the I2C program;

Cayden has sent the register configuration file to you, so is there any other file your need us to provide?

Hello Zhang,

Zhang Liang said:

We connect both the system and battery, the output voltage will be cycle(11mS) drop more than 7V when the output current is 1A;

I'm confused on the scope capture. Is the yellow signal the system voltage?

What is the measure system voltage?

Is the voltage dropping to 7V? or is it dropping 7V?

The system voltage is related to the to the Min_Sys value and Charge Voltage value, and you are reading these values as 0x00. If this is the case, I'm confused how you are seeing any voltage on SYS load.

I want to try and keep both of your questions together:

I didn't see any obvious issue with your code, but I might be missing something, Do you have a way to capture the I2C writes to the BQ24773? Such as Saleae I want to see what is being written to the device.

Best Regards,

Christian.

1. The yellow signal is the system voltage (also the buck output)

2. The waveform above is captured when the load is light（100mA）, and you can see the small valley on the system voltage;

    While system load changes to 1A or heavier ，the valley voltage downs to 7V，with the same cycle.

3. The system voltage is 13.5V by default without any I2C opreation , and the related registers are 0x00, which is exactly makes us confused too.

4. OK, I will try Saleae soon.

Hello,

Thank you, I'll wait for Saleae results.

Best Regards,

Christian.

With the help of Saleae， we find something abnormal and we are working on it.

Besides, we want to know:

Is it normal for the BUCK's output to be unstable when the battery is removed?

Could you please repeat it on the EVM board?

Hello Team,

No, It is not normal, and I was not able to repeat on EVM. I recommend resolving the issue with the I2C writes, and see if this has any affect on the output.

Best Regards,

Christian.