LTC6804-2 VOV

Question

Hello, 
 I'm facing some problems regarding OverVoltage cells (when I check the Status Register Group B). I have a LTC6804-2 with 12 cells connected. The ADC voltage readings are correct:

VC1 = 41538 
 VC7 = 40528

VC2 = 38785 
 VC8 = 40504

VC3 = 40256 
 VC9 = 40138

VC4 = 40219 
 VC10 = 40567

VC5 = 40232 
 VC11 = 40495

VC6 = 40532 
 VC12 = 40548

At the begining I set the voltage thresholds for OV and UV (Configuration Register Group): voltage_vuv_threshold = 1563 (that it is 2.5 V) voltage_vov_threshold = 4094 (that it is 8.5V) 
 After writing this information in to the LTC6804, I read back the register in order to check if those values are properly stored (and they are ok). 
 Then, I check the Register Group B (CxOV & CxUV flags). All bits related to OV cells are set to 1, no matter what value I set as OverVoltage threshold: vuv_flags = 0 (all cells haven't gone below 2.5V) vov_flags = 4095 (all cells have gone above 8.5V) 
 I do have the suspicius that no matter I'm writing in Configuration Register Group, but value is 0, that is why I don't have UV but I have OV. What it is strange is when I read back the register value it has the values that I wrote. 
 Any of you have any clue on this? 
 
 Thanks in advance, Regards, Roberto

SideshS · Answer

Rob10 said: voltage_vov_threshold = 4094 (that it is 8.5V) 
 Configuring 4094(0xFFE) into VOV bits in the Configuration register corresponds to configuring an Over Voltage threshold at 6.5504V (=4094*16*100uV) 
 Rob10 said: Any of you have any clue on this? 
 What you observe is strange and is not expected if you have configured the bits in the Configuration register as desired. So we would suggest rechecking the way you write into and read from the configuration register of the device. Please ensure you are following the expected order of sending and receiving the bytes as explained in the Bus protocols section of the Datasheet(Page No. 48).