BQ24160: BQ24160 with I2C

Jingle,

Input source selection should not be dependent on battery. What are the voltages of each battery at plug in? What do the I2C status registers report after battery1 plug in in each case?

Hi Jeff,

          Thanks for your reply, two battery voltage are VBAT1=3.73V, VBAT2=3.62V , We understood the input source selection should be dependent on the Charger

          IC BQ24160,

          we use the MCU to read the BQ24160 register by I2C bus to check the power input source, and the default value is 0X01 to show preferred source when

          both connected, if the MCU read data is same, the result is PASS/OK, otherwise, it's FAIL/ERROR.

          Note: ( Vbat1=3.73V with I2C pull high,   Vbat2=3.62v without I2C pull high)

          From the following pictures, you can know the ERROR, when we use the battery 1 with pull high. (VBAT1-1/VBAT1-2)  

           VBAT1-1

           

          VBAT1-2

                   

          From the next picture, the battery 2 is OK (VBAT2-1/VBAT2-2) 

           VBAT2-1

           

          VBAT2-2

           

     It seems to something wrong about the difference battery,maybe if the charger i2c stard faster than others, leading the back of voltage,

         So please teach us what's happen?

         We need to reply quickly to our customer and to do the MP.

BR,

Jingle

Hi Jeff,

            What do you mean? we will charge battery from 3.0v to 4.2v and set USB D+/D- closed, 

            So if you say the battery is above VBATREG 3.6V, charger will judge battery OVP, this is very crazy.

            As previous mentioned, please reconfirm our question and reply to us,

BR,

Jingle

Jingle,

The default VBATREG is 3.6V.  If the host has not changed the VBATREG register from 3.6V to 4.2V before attaching a battery > 3.6V, the charger either thinks the battery is fully charged or in overvoltage.  In that state, the charger will not perform D+/D- detection and defaults input current limit to 100mA.

Hi Jeff,

             OK, we understand this situation, so we have set charge voltage up to 4.3v, I think it's OK,

             But our question is why MCU has read the different value from BQ24160 when dual power input (USB and DC_IN) and different BAT1 and Bat2 ?

             This seems to have nothing to do with D+/D-,

             We want to know why the I2C pull high of BAT1 will affect the value of MCU reading?

BR,

Jingle

Jingle,

I have been in the lab working the EVM and it appears that a noise spike on D+ at plug in is causing the D+/D- to fail and always default to 100mA, regardless of SDP (100mA) or DCP (1500mA). If you force D+/D- detection in I2C, it works well. Tomorrow, I will add an RC filter on D+ line to eliminate the noise spike and try again.

Hi Jeff,
I'm confused that why the signal pull high of Battery I2C has affect the signal D+/D- of USB?
If it's true, but i want to know why both power (dc_in and usb) input didn't sometimes detect DC_IN because of battery i2c pull high?

BR,
Jingle

Jingle,

With VBATREG=4.2V and different battery voltages, I cannot reproduce what you are seeing. The charger correctly recognizes which input source is in use. However, my I2C bus is always pulled up to 3.3V, which is the maximum voltage that we have tested for I2C pull up. I will need more time to modify the EVM so that I can pull up I2C to the battery voltage.

Jingle,

I removed the internal pullups to the EVM's communication box and am now externally pulling up the I2C lines to the battery voltage. I see the correct detection of "charging from IN" or "charging from USB" regardless of battery voltage (2.5V-4.9V).