Not sure about mupltiplexing but I am using a ws2803 (18ch version of ws2801) and no issues with burning up. I had the same trouble with the tlc5940's and hate them now for being so easy to blow up, the ws2803's have been going like champs and don't burn up if you flick fluoros on n off. They're current source, I'm running them through hex inveters to n channel mosfets to drive rgb strips. Just wish they had built in inverting like the ws2801 has.