gene heskett wrote: >> >> Yes, I put a 1 uF cap on the back of the board directly under the driver >> chip. One for the >> low-side driver and logic, one for the floating high-side driver. I've >> been using this general >> topology since 2004 or so in my brush servo amp designs. >> >> Jon >> >> > Sounds like I've got a skuttle, carrying coal to Newcastle. :) > I used to have 0.1 uF there, which was definitely marginal. When I upped the size of the FETs I used, the high-side drivers started cutting out on their undervoltage trip. Also, the current pulses drawn when the low-side transistors were turned on caused a dip in the 12 V logic rail (I used 4000 CMOS in the brush servo amp) that upset the sense amp in the logic-out optocouplers. This quirk took me a long time to find. Upping a bunch of caps to 1 uF took care of this.
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