BQ76930: Design help requested for BQ76930

Hi Mike,

I understand this can be a confusing device for someone who is not very experienced with battery electronics. I think the thing that will help you most is to look at reference designs using this device or other devices from this product family. Here are the links to the reference designs:

http://www.ti.com/tool/TIDA-00449 

http://www.ti.com/tool/TIDA-00792 

http://www.ti.com/tool/TIDA-01093 

http://www.ti.com/tool/TIDA-010030 

http://www.ti.com/tool/TIDA-00255

There are a few other critical documents you want to have handy in addition to the datasheet. The app note "bq769x0 Family Top 10 Design Considerations", the FAQ, and the EVM User Guide all contain information that will be very helpful. Additionally, you will be able to find the answer to many of your questions by searching the E2E forum since this device has been out for a while there are lots of answered questions to learn from.

For your questions:

1. How to wire up my 8 cells to the device.  I referred to the 'Cell Connections' table in the specification document but I found Cell 5 details confusing.  This cell is wired to VC6 and VC5b but I don't see any short required between VC5 and VC5b - are these 2 pins connected internally or have I misunderstood the table?  I've attached a schematic showing how I've interpreted the table - not sure whether the short I've added between VC5 and VC5b is necessary.
   The cell connection table is correct and you can use this to short the appropriate pins. VC5B is the bottom of the 6th cell - internally the device has the cells grouped by 5. You do not want to directly short VC5 and VC5B. I recommend looking at TIDA-010030 as an example since it uses 13 out of 15 cells.
2. In the 'Typical Applications' section, the schematic shows each cell connected through a resistor denoted as Rc (guessing this is a current limiting resistor?) and adjacent cell lines connected with a capacitor, denoted as Cc.
   These are the filters for the voltage measurement pins. Yes, these are necessary and have min/max values in the datasheet.
   Are these required if the BQ76930 is to be used solely for
      a) cell voltage measurement   
      b) temperature sensing via the 2 thermistors.
   
   If they are needed what is their purpose, and what values should they have?
   
   
3. In a similar vein, there are many other components on the typical application diagram, for example, the CHG/DSG FETs, lots of capacitors and resistors on the RHS of the schematic.  Which, if any of these, do I need to include in my basic circuit?
   Excluding components will have consequences. The purpose of each component is explained either in the datasheet or the Top Ten design Considerations app note. If you are not sure, the best thing to do is to keep the same components.
   
   
4. The thermistor connections puzzle me.  I was expecting there would be 2 outputs (there are - TS1 and TS2) and that these would be connected to ground (each via their respective thermistor).  However, the typical application schematic shows them connected quite differently.  TS1 appears to be powered by VC1 while TS2 is somehow connected to VC5x (which is described as being Thermistor #2 negative terminal). I'm struggling to understand the logic behind this set of connections.  
   The operation of the external thermistor pins and how to connect them is described in the datasheet. It uses an ADC and provides a pull-up pulse periodically to take a measurement. 
5. How do I configure the device?  I see references to an evaluation board and software that is prohibitively expensive.  Can I configure the device using i2c? I highly recommend investing in the EVM and EV2400. You can of course configure the device using I2C, but since you have not used a battery monitor before, there is much to learn and it will be more difficult to debug without the software. Alternatively, you could use the EV2400 to communicate directly with the device on your board if you can make the connection.

Best regards,

Matt

Hi Matt

I have taken your advice and purchased the bq76930 evaluation module and EV2400 interface board.

On my computer I run Ubuntu 18.04 and use VMWare to run my Windows operating systems.  The evaluation module software has installed ok on Windows 10, however I have run into an issue under Ubuntu when I plug in the EV2400 cable.  It fails to enumerate the EV2400 device as shown in the following syslog output.

Reading various forums it has been suggested that this type of error is caused by the device pulling more power than the USB port can provide, however I also get the same error when I use a powered USB hub.

Wondering if anyone has successfully got the EV2400 running successfully using Linux as host, and Windows as a guest OS.

I should also point out that I have this running ok using my wifes laptop running Windows 7 natively, so I know the EV2400 is working ok.

May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.118651] usb 1-1.2: new full-speed USB device number 8 using ehci-pci
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.230229] usb 1-1.2: New USB device found, idVendor=0451, idProduct=0037
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.230231] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.230233] usb 1-1.2: Product: EV2400
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.230234] usb 1-1.2: Manufacturer: Texas Instruments
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.230236] usb 1-1.2: SerialNumber: 49DF886E27000F00
May 21 16:46:06 nomadau-ThinkPad-W530 kernel: [ 3230.233169] hid-generic 0003:0451:0037.000F: hiddev2,hidraw4: USB HID v1.01 Device [Texas Instruments EV2400] on usb-0000:00:1a.0-1.2/input0
May 21 16:46:06 nomadau-ThinkPad-W530 mtp-probe: checking bus 1, device 8: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2"
May 21 16:46:06 nomadau-ThinkPad-W530 mtp-probe: bus: 1, device: 8 was not an MTP device
May 21 16:46:06 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0/0003:0451:0037.000F
May 21 16:46:06 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0
May 21 16:46:06 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2
May 21 16:46:31 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0/0003:0451:0037.000F
May 21 16:46:31 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0
May 21 16:46:31 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0
May 21 16:46:31 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2:1.0
May 21 16:46:31 nomadau-ThinkPad-W530 kernel: [ 3255.322456] usb 1-1.2: reset full-speed USB device number 8 using ehci-pci
May 21 16:46:31 nomadau-ThinkPad-W530 kernel: [ 3255.402397] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:31 nomadau-ThinkPad-W530 kernel: [ 3255.590376] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:32 nomadau-ThinkPad-W530 kernel: [ 3255.778376] usb 1-1.2: reset full-speed USB device number 8 using ehci-pci
May 21 16:46:32 nomadau-ThinkPad-W530 kernel: [ 3255.858369] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:32 nomadau-ThinkPad-W530 kernel: [ 3256.046375] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:32 nomadau-ThinkPad-W530 kernel: [ 3256.238371] usb 1-1.2: reset full-speed USB device number 8 using ehci-pci
May 21 16:46:32 nomadau-ThinkPad-W530 kernel: [ 3256.654362] usb 1-1.2: device not accepting address 8, error -32
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3256.734363] usb 1-1.2: reset full-speed USB device number 8 using ehci-pci
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.150380] usb 1-1.2: device not accepting address 8, error -32
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.150851] usb 1-1.2: USB disconnect, device number 8
May 21 16:46:33 nomadau-ThinkPad-W530 upowerd[1457]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.230362] usb 1-1.2: new full-speed USB device number 9 using ehci-pci
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.310355] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.498372] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:33 nomadau-ThinkPad-W530 kernel: [ 3257.686444] usb 1-1.2: new full-speed USB device number 10 using ehci-pci
May 21 16:46:34 nomadau-ThinkPad-W530 kernel: [ 3257.770356] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:34 nomadau-ThinkPad-W530 kernel: [ 3257.958358] usb 1-1.2: device descriptor read/64, error -32
May 21 16:46:34 nomadau-ThinkPad-W530 kernel: [ 3258.066500] usb 1-1-port2: attempt power cycle
May 21 16:46:34 nomadau-ThinkPad-W530 kernel: [ 3258.670350] usb 1-1.2: new full-speed USB device number 11 using ehci-pci
May 21 16:46:35 nomadau-ThinkPad-W530 kernel: [ 3259.086408] usb 1-1.2: device not accepting address 11, error -32
May 21 16:46:35 nomadau-ThinkPad-W530 kernel: [ 3259.166369] usb 1-1.2: new full-speed USB device number 12 using ehci-pci
May 21 16:46:35 nomadau-ThinkPad-W530 kernel: [ 3259.582349] usb 1-1.2: device not accepting address 12, error -32
May 21 16:46:35 nomadau-ThinkPad-W530 kernel: [ 3259.582507] usb 1-1-port2: unable to enumerate USB device