There are lots of standards, and I sometimes find it confusig, where people dont really know what is the acceptable standard for software lifecycle in medical device, acceptable by the FDA and CE. Some vendors also claim t support specific standards, such as 21CFR 820, which has nothing to do with softwaare lifecycle in specific.
I came to the final conclusion:
The acceptable standard for software lifecycle management is IEC 62304, you can find some data about it in this blog
The ISO 14971 talks about risk management
The 21 CFR part 820 is more or lessthe same as ISO 13485 and they don’t talk about software lifecycle in particular (see this link for reference: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?cfrpart=820 ). The software lifecycle is only one part.
The FDA guidelines for software lifecycle managemnt are specified in the General Principles of Software Validation, and they are very hard to understand. Thats why it is recommended to use the IEC 62304 guidelines.