Quote:
Originally Posted by AdamHeard
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The fix for the SD540 power output is probably just a change in the MOSFETs or thermal characteristics. They probably just used MOSFETS with a higher Rds(on). I'm not sure of the actual topography of the SD540s, but I get an equivalent Rds(on) of ~ 17 mOhms with the SD540s. In comparison, the Victor SP has an equivalent of ~ 4 mOhms. When I say I don't know the topography, it'll be an H-bridge, but how many parallel MOSFETS there are on each leg is key. Also, I'm guessing the SRX has an additional current sense resistor over the SP, which would explain why the Victor SP tests better (just my guess). As for the SD540s, I'm betting when they designed it, they trusted the MOSFET data sheet. MOSFET Rds(on) specs in datasheets are some of the biggest lies ever. They'll give you the Rds(on) with a junction temperature of 20 degC on the front page, but when you heat it up to ~100 degC, it can change drastically. Always check the graphs.