I’ll be getting a decorative but useless PC board next week. It is a good thing it only cost me $50.
It turns out that the H-bridge that was recommended to me, Infineon’s TLE-5205, is made of unobtanium. I thought I had checked Digi-Key’s stock before starting my design, but I must have mistyped the part number, as Digi-Key customer service just called me to say that they haven’t had any since Sept 2010 and don’t expect any in the next 18 weeks. They do have a few TLE-5206-2 still in stock, probably because it is a less useful part, not having the Hi-Z output state. I must have checked that part instead of the TLE-5205-2. Probably no other distributor has any TLE-5205-2’s either, if Infineon has been unable to make any since last September.
I didn’t know that Digi-Key had customer service reps working at 8p.m. on a Saturday night—it is good to know that a supplier cares enough to keep engineer hours.
In any event, I’m going to have to completely redesign the board. The TLE-5205 is unavailable even in the surface mount packages, so I can’t just change packages. I’ll have to find and use a different H-bridge, which will be a major pain, as the TLE-5205 came close to being ideal for this application. I suspect that since the 5206 is still available, that the problem might be with the freewheeling diodes. Since the 5206 always has either the high-side or low-side on, it doesn’t need Schottky freewheeling diodes. Unfortunately, most of the other H-bridges I’ve looked at expect external diodes—the TLE-5205 was attractive because it had built-in diodes, saving a lot of board space.