BQ25703A: Reference configuration for 2S Li-Ion charging

I'm attempting to wade through the eval kit registers at this point but the board does not seem to respond.

I'm following the section 2.4 procedure, specifically steps 1, 2, and 3 of 2.4.1 which all work.  However, step 4 has 6.1 volts at the system connector and step 5 has 0.8V at the battery connector.  BQSTUDIO has "Device ACK Error" displayed at the top.  AutoRead is set to 1-second and there seems to be no activity on I2C.  (By the way, despite the eval kit pdf showing the use of the SMB socket on EV2400, I'm using the I2C socket because this is the BQ25703 I2C device.  SMB didn't make a difference anyway.)

How do I make this work?

Hi, Jon,

Thanks for your interest in BQ25703A. I understood your frustration when first attempt to use a new device. BQ25703A builds default register values inside the part. After power on reset (POR), the default value will load into the registers based on the CELL_BATPRESZ setting. 

It is a good idea to play with the EVM as a starting point. I didn't see anything wrong. But "Device ACK Error" is alarming. Make sure to follow the instruction step by step, for example, setting the I2C address as "D6(6B)". Another tip is to disable watchdog timer during prototype stage. Using I2C socket is correct. 

See default register values below.

Tiger,

Thanks for the reply and for the default register values.

I'm dealing with the EV2400 at this point.  It's brand new but does not seem to work.  I suspect that's the reason for my "Device Ack Error" and "Not able to find a free communications adapter" messages.  According to other posts I've tried updating the EV2400 firmware but the window comes back with "Error:  No Free EV2400s Detected."  I'm looking into that.

You mentioned that the chip, after POR, would load default values into the registers based on the CELL_BATPRESZ setting. I have that set for two cells.  For which chemistry?

Jon

Tiger,

Additional information collected today.  I connected my EV2400 to a different PC and it seems to work fine.  The BQ25703 is now responding.  Your default reg values, coupled with a complete reading of the register map will get me on my way.  My question above, remains.  Which chemistry?

The reason I selected the BQ25703 is that I needed a buck-boost solution that would manage power to the application load, and charge a two-cell Li-Ion battery pack, in addition to switching in the battery to the load even if the input power was disconnected.  Will this do the job?

Thanks.

Jon

Glad to hear the progress. The BQ25703A supports Li-ion battery. If you set for 2S, the max charge voltage is set 8.4V by default, the min system voltage is set 6.144V by default.  (You can adjust them if you want.) However, it does require a host to send the charge current and turn-on/off the charging by command. Charging a battery or supplementing a system load are the basic functions of the part. No problem at all.