BQ28550 change CUV Threshold

Hi Rene

I am not certain I understand what you  are asking here. There is a minimum voltage requried to power the processor of the chip and i think it is in the 2.5V  range. You do not need to start the system using the shut down command. As long as you have your voltages above the CUV threshold you should be fine. If it goes below, the discharge fet should turn off. It is usually not recommended to discharge your battery to voltages lower that the minimum voltage specified in the data sheet wch typically is 3V. If using a power supply to valuate the gauge ,use voltages higher than 3V.

thanks

Onyx

Hi Onyx

if the voltage went below 3V(CUV threshold) then the discharge fet should turn off. This works, but when I connect the power supply for charging the discharge fet doesn't turn on. This is my problem.

If I send the shutdown command the discharge fet turnes off and when I connect the power supply for charging the discharge fet turns on automatically. Why doesn't that work when the voltage goes below 3V?

Rene

Hi Rene,

What do you have the CUV_Recov_chg bit set to in the operation configuration register. Whatever you have it set to now, toggle it to the opposite value i.e, if set, clear it. If clear, then set it and repeat your experiment. Also, what do you hav your CUV recovery threshold set to? The cell voltage will have to go above this value in order to recover from a cell undervoltage condition.

thanks

Onyx

Hi Onyx,

the CUV recovery threshold set to 3000 mV and the CUV threshold set to 2800.
I have the CUV_Recov_chg bit set from 0 to 1.
If the voltage went below 2800 mV discharge fet turnes off (OK), but when I connect the power supply for charging the discharge fet doesn't turn on. Same Problem.

From Technical Reference Manual (sluu513.pdf)
"5. Read the original target row first through a block read command 0x2F before updating.
6. Store original data in a memory array so the appropriate byte(s) can be updated.
SMBus block read cmd = 0x2F, length = 32 byte."

But the description for the "Table C-1. Class: 1st Level Safety, Subclass: Voltage (continued)" and so on is not correct.
Is this a chip problem or a description problem?

thanks
Rene

Hi Rene,

Extract a gg file from  your device so I can test on my EVM to see what the issue is.

thanks

Onyx

Hi Onyx,

I don't have an EVM tool. Can I extract the data over i2c?

I'm doing to change CUV the following steps:

1. 0x0112 -> 0x00

2. send 0x2F and read 33 bytes.  (because I have to write 33 bytes and the last byte is not the checksum)

3. here the output: 20 E1 F0 10 68 10 04 10 9A 10 36 10 36 0F A0 02 09 C4 02 0B B8 17 70 02 00 C8 17 70 02 00 C8 08 02

I changed the values 09 C4 to 0A F0  (2500 to 2800)

4. send 0x2F and write 33 bytes.

5. new read for verify

I'm doing to change CUV_RECOV_CHG the following steps:

1. 0x010F -> 0x00

2. send 0x2F and read 33 bytes.  (because I have to write 33 bytes and the last byte is not the checksum)

3. here the output: 20 FF 62 01 2C 00 02 2A 30 0E 10 00 00 1B 00 00 80 00 14 0A 19 02 58 0A F0 06 D6 0A 00 0A 05 00 32

I changed the values 1B 00 to 1B 12  (CUV_RECOV_CHG and SLEEP allow)

4. send 0x2F and write 33 bytes.

5. new read for verify

Rene

HI Rene,
How do you plan on programming multple devices? I need either a gg file or srec such that I can test your setting on my EVM to see why the discharge fet is not coming on. Can you hook your boad to either an EV2300 or EV2400 and extract the files i requested.
You method forchangin g the CUV thresholds seem right. When you do the new read to verify, are the changes you made effected?
thanksOnyx

Hi Onyx,

I hope I found the problem. If I disconnect the main unit from the gas gage and discharge then it works fine. The discharge fet  turned off at 3V and if I connect the charger the discharge fet  turned on.

But If the power consumption is very high (600 mA) and the discharge fet  turned off, then the discharge fet doesn't turn on. 

Could be due to the precharge settings?

Rene

Hi Rene,
If you could send a gg or senc or dfi file from you device this will help in debugging. Can you verify to see what your NR bit is set to? Since you are saying when you disconnected the main unit the discharge works fine, I am suspecting the state of the NR bit is affecting the recovery. Can you have the NR bit set?
thanksOnyx

Hi Onyx

can you tell me where i find the NR Bit?

thanks Rene

Hi Rene,

pls reference the TRM found in the link below

 

http://www.ti.com/lit/pdf/sluu513

 

thanks

Onyx