Other Parts Discussed in Thread: BQ76PL536
Hello everyone,
I'm currently programming a BMS and I find myself constantly hitting a wall on the board I've designed following the datasheets, the application notes and the refence designs that Texas Instruments provides. It doesn't seem that there's a great difference among the different designs I've looked but I'll post it here anyway. There are some resistors and capacitors changed because they were wrong.
The design has 26 series and two connectors that bring the voltages I want to read.
My problem started when I tried to read the cells on all the five devices that my design has, I was able to read three devices so I didn't think that i was going to have any problem, but when I plugged in the second connector to read the fourth and fifth device all the voltages, from the first one to the twenty-sixth are just wrong. All the registers I read are on 1 so the measures were 25 V instead of 3.86 V.
Then I tried to assign and read the address register of each one, but when I reached the third device the address was 255. As it's a wrong addres, I reset every device and start again but when this event takes place, after assigning the first address I also read 255 from the first one. (Picture below)
When I unplug the second connector, leaving the forth and fifth devices unpowered, I'm able to assign the third address. The program resets the devices when it reads that the forth address isn't right:
Now I've tried to read the device status, as it said that i've got an Alert and a Fault activated I also read them and the values were the following ones for the devices with an address assinged.
First device:
Device status: 225 = 11100001
Alert: 128 = 10000000
Fault: 9 = 00001001
Second device:
Device status: 225 = 11100001
Alert: 128 = 10000000
Fault: 11 = 00001011
The device status tells me that there's an address assigned correctly, an alert and a fault signal.
The Alert says that there's no address assigned, which is really weird when the device status says that an address has been assigned
The Fault register gives me more information, for example it says i've got a Power-on reset error, a COV and a CUV.
I find it really curious, the device status doesn't show that an UVLO event happened to have a power-on reset condition. I've looked with an oscilloscope and the VREG50, LDOD, LDOA have a constant value of 5 V.
Maybe something is messing with the SPI bus? I don't know what else to do.
Thank you for your help.
Alex Torrubia
