BQ500215: LED behavior seems more complicated than described in datasheet

Hello!

Due to holidays, our response time is slower than usual. Someone from my team will get back to you shortly.

thanks!
Gautham

Hello
For both Question 1 and Question 2, Blinking Red LED -- This could possibly be caused by input power limit circuit. Double check the input voltage to make sure it is not limited.

For Question 3 the " - " will be not used and off.

Hi Bill, thanks for you reply.

As to Q1, I am quite sure power limit circuit doesn't work,  because after I removed the metal object(a tweezer), 

I check the charging current from via a app of our device, it is normal.

output voltage is 9V as per our setting, and it keeps 9V when red LED blinking nonstop.

You can reproduce such situation in lab with EVM.

As to Q2, I now have some clues.

when put the device into the charging cradle, sometimes authentication between BQ500215 and BQ51025 will fails(it is said this is a TI bug),

and PMODE pin of BQ51025 keeps high, but we force BQ51025 to work in 10W mode by disable 2X current limit function, then the device will ask for more than 5W, 

then  the primary controller detects this conflict, so red LED blinks.  In our design ,when CPU detects PMODE high, we will send a restart command to the primary controller, but the LED cannot be reset by this command.

Sawtooth wave of CH4 means LED is blinking. And you can see it seems LED cannot be reset by restart command.

So the problem is, can LED be reset directly by restart command?

You can also reproduce this red blinking issue in lab with TI EVM

My test procedure with BQ500215EVM and BQ51025EVM:

1)      Put RX on the surface of TX, insert a tweezer into between ,turn on the DC power connected to TX, then pull tweezer out, system will be powered on in 5W mode with PMOD high.

2)      For this RX board, the default set is 0.85A for 5W mode.Disable 2X current limit of RX via TI tool, and current limit is then 1.7A.

3)      Connect RX output to an electronic load, and increase the load current from 0.7A to 1.3A(5.5V*1.3=7.15W), we can see from the oscilloscope, output voltage maintains for 6s and then drops, while TX red led blinking  also is triggered, and LED sometimes will restore after current reduces, sometimes won’t.

Bill Johns said:

Hello
For both Question 1 and Question 2, Blinking Red LED -- This could possibly be caused by input power limit circuit. Double check the input voltage to make sure it is not limited.

For Question 3 the " - " will be not used and off.

If the information above is not clear, please let me know.

Hope for your further information.

Wolf