Hello, we are having a problem with corrupt registries in the BQ27010 we believed may be caused by spurious RF on the HDQ line introduces from the working environment. Our (1S1P) packs work in a high RF environment and recently we have been having battery packs returned that seem to develop corrupt registry values after a period of time (infant mortality, not defect on arrival). The defective batteries have two symptoms:
1. The battery was fully charged but could not established communications with the host.
2. The battery was fully charged and could establish communications but had corrupt values for a number of registry entries.
For the batteries that don't communicate, forcing a reset by removing interrupting the power resolves the issue and communications ar restored.
For batteries that can still communicate, a reset restore functionality. A cycle test on the restored batteries does not show any registry corruption or anomaly.
The working theory is that the corruptions appear over a period of time until a corruption prevents the battery for communicating at all.
Some registries appear to be more susceptible to corruption.A sample of 38 batteries with this condition showed:
Registry Count Registry Description
Cycles 21 Cycle count invalid, by several orders of magnitude
LMD 15 LMD invalid, by several orders of magnitude
NAC 15 NAC invalid
GPIEN 5 Indicates that a general purpose I/O pin is enabled as an input - incorrect for this battery
PRST 2 Partial Reset – Intended for use during manufacturing.
Other 2 Other registry entries changed
WRTNAC 1 A command to write a new value to NAC - should not be set
This battery has been in use with the same configuration for many years. Previously we had similar results on some prototypes that were missing the zener diode on the HDQ input.
The symptoms are very similar to what is described in SLUA460, ESD and RF mitigation in Handheld Battery Pack Electronics, specifically the sections concerning ESD mitigation "For example, RAM corruption may occur as a result of ESD and is unacceptable if it causes the misreporting of available capacity or other critical information".
We have the typical zener diode protection on the HDQ input and have checked that they are working correctly on the effected packs.
Questions/comments/suggestions? Has there been any changes to the mask/process that might cause this effect? What type of interference on the HDQ input would cause this type of corruption? Any suggestions would be greatly appreciated.