BQ27750: Problem: Communications and interfacing with new chip

Dallin Lloyd

Part Number: BQ27750
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hello

I have a newly designed board that is using a BQ27750 Gas gauge Battery management chip. I also have the EV2400 USB -> I2C interface. When connecting the board to the I2C interface i am unable to communicate with a new chip.

My schematics very closely match the schematics that are outlined in the BQ27750EVM (evaluation module) and i have also tried to pull up / pull down the I2C lines (3.3V pull up)

Battery management studio did not have the appropriate .BQZ for the BQ27750 chip. I was able to locate 1750_0_04-bq27750.bqz and added it to the configuration for the program.

I then located: bq27750_b0_04_build_12.srec and tried to flash the chip with this .srec file. The statement at the bottom of battery management studio said: No acknowledge from chip (or something similar)

My team and I are running out of ideas on how to communicate with this chip. Can you please provide me with some input on how to communicate with the BQ27750

Thanks for your time

-Dallin

over 7 years ago

0 Onyx Ahiakwo over 7 years ago

TI__Guru* 76230 points

Hi Turbo,
Did you apply a charger voltage to wake the device up from shut down mode?
thanks
Onyx

0 Dallin Lloyd over 7 years ago in reply to Onyx Ahiakwo

Prodigy 160 points

Hi Onyx,

I did not yet apply a charger voltage. Instead I installed a switch (s1 on the development board) that bypasses the mosfets. Do i need to have a voltage difference between the terminals to wake the chip?

0 Onyx Ahiakwo over 7 years ago in reply to Dallin Lloyd

TI__Guru* 76230 points

no you do not. The packp pin just needs to see a voltage greater than the charger detect voltage which i am assuming it is seeing given you have the switch.

Can you place a scope on TS pin so we ensure that the gauge is functional? The TS pin will be pulsing every second if the gauge is powered on and the processor is running.

if that isn't the case then it means your board isn't functional. How are you communicating? Are you using an ev2300 or ev2400 and bqstudio?

thanks
Onyx

0 Dallin Lloyd over 7 years ago in reply to Onyx Ahiakwo

Prodigy 160 points

I do not have access to a scope currently. However i can see that approx every second (fluke multimeter) that there is a little voltage spike. So i am assuming that the processor is running.
*at this point i found that the board house placed a capacitor on the TS pin instead of a 10Kohm resistor as per our schematic. I am unsure if this would cause something to go wrong with the BQ27750

I am communicating with a EV2400 and BQstudio

0 Dallin Lloyd over 7 years ago in reply to Dallin Lloyd

Prodigy 160 points

I am going to get my hands on a scope so i can check the TS pin. Is there anything else i can use for verification?
For example. what voltage should i see on the I2C lines? I have seen discussion about 1.8V and 3.3V. when everything is connected, i see 0.8V nominal on SCL and 3.1V on SDA.

0 Onyx Ahiakwo over 7 years ago in reply to Dallin Lloyd

TI__Guru* 76230 points

A capacitor on your TS pin instead of a thermistor??? You will have to thoroughly review your board because at this point it could be anything that might be wrong. I would recommend you obtain an evm so you can do a comparison between both boards as well as the signals on each pin
thanks
Onyx

0 Dallin Lloyd over 7 years ago in reply to Onyx Ahiakwo

Prodigy 160 points

Once i pulled the "capacitor" i realized i was not making good contact. We are going to obtain a eval board and verify again it. Thanks for your help!

0 Dallin Lloyd over 7 years ago in reply to Onyx Ahiakwo

Prodigy 160 points

Got data communication. You were correct. There was a hardware issue on the board that became obvious after using a scope.

On a side note: i was unable to find much information on the interrupt function of the BQ27750. Is there other resources available so i can use to learn more about it?

0 Onyx Ahiakwo over 7 years ago in reply to Dallin Lloyd

TI__Guru* 76230 points

Do you have the technical reference manual for the device.

See below

thanks

Onyx

0 Dallin Lloyd over 7 years ago in reply to Onyx Ahiakwo

Prodigy 160 points

I did. after a bit more digging i was able to find the information i needed. Thank you for your help Onyx!

Power management

Power management forum

BQ27750: Problem: Communications and interfacing with new chip