EEPROM Fault

[Guest]

hi there guys, i just want some advice from you. I have encountered some problem in soft stsrters. The indicated fault is failure of EEPROM, this already happen twice in our plant in span of one month. What could be the pssible case of this?

[jraef]

The down side to EEPROMs is that they have a finite write-life; you can only re-write over them so many times, typically 10,000. That seems like a lot, but if you update too often it adds up.

 

Usually, the problem you are describing can be attributed to a specific power failure mode. As the line power is dropping, the EEPROM needs to be updated at the last possible moment prior to the DC bus level fully colapsing. If there is a significant amount of line noise, particularly common mode noise, as the voltage is failing, the EEPROM can be corrupted. The most common cause for this type of corruption is when there is a ground fault. We found this problem in some of our first designs and added additional caps to the DC bus, as well as an "early warning system" that would give us a heads-up on starting the update process, but abort if the power did not ultimately fail (so that we didn't unnecessarily consume write-life). Other manufacturers deal with the limnited write-life either by NOT updating the EEPROM unless the user commands it manually (which rarely happens), or only updating the EEPROM at specific intervals. These solutions come with their own set of problems, such as losing data on power loss. Saftronics / Emotron, Baldor/ Fairford and earlier Benshaw starters are examples of EEPROM systems that loose data on unexpected power loss.

[marke]

I agree with Jraef, the most likely cause is an unexpected power down/brown out situation where the voltage is dropping too low to write to the EEROM.

Writing to an EEROM is relatively slow and requires full supply voltage. If the processor does a dump to EEROM at power down, there will be a number of parameters to write. Under normal power down situations, there is sufficient storage in the power supply capacitors to enable a complete dump. Under brown out situations, half the energy can be gone before the decision is made to dump. At this stage, there can be insufficient energy to cary out a full dump. The problem with a brown out, is when do you determine that it is a brown out that requires a dump and when can you ride through. You certainly do not whant the starter to shut down every time there is a hint of a brown out, most people want the start to to keep going as long as possible.

 

Best regards,