On Sun, May 18, 2008 at 1:19 PM, Forrest Christian wrote: > Apptech wrote: >> At $US10 in 5000 quantity from Digikey it's a bit dearer [tm] in >> component cost than a discrete solution. Component cost is far from >> the only consideration, but $10 goes a longway on such things >> But, a nice solution where raw cost is not too important. >> >> http://www.national.com/ds/LM/LMD18200.pdf >> > I'm using it in a situation where a high-accuracy timing source (1 PPS, > +- 1 uS or so) is needed, and must be provided to the equipment by > putting a 120us hole in the supply every second. Because of the 1uS > "jitter" requirement, I have to drive the power line not only high but > also low to drain off any power left over in the cable capacitance... > so I need both high side and low side drivers, and all the circuitry to > prevent shoot-through and the like. Plus, I need short circuit and > thermal overload shutdown since these faults can and do occur. > > But like I said, I would love to find something cheaper.. $10 each > (they are just under $11 at Qty 100) is a bit expensive... but when you > figure out that they contain two high-side fets, two low-side fets, all > the driver circuitry (minus a few caps), and thermal and short-circuit > protection, it sure seems like a reasonable price to me. I would also be interested. I do not need the low side FETs. But greater than 100KHZ switching and 3A (higher is better) capability will be necessary. Multiple channel capability is desired. It is possible to use a MOSFET (NMOS or PMOS) and a good MOSFET driver (Microchip TC4451/4452 are good). But then you do not have those protection built-in. There are other challenges as well. For example, if the user high side voltage can be as high as 60V, many MOSFETs will need protection because of the gate-source breakdown voltage. There are many high side switches, like ST VN808 or VN340 which are widely used in discrete output module for PLCs. But they provide limited driving capability. Xiaofan -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist