Yeah... I'm going that route. I did the math on appropriate FETs and=20 drivers and it works out the same as this monolithic device, assumed=20 proven to work. This will be for a window motor, running in a car at 12V. Cheers, -Neil. On 1/2/2015 4:18 PM, Jean-Paul Louis wrote: > Neil, > > Why trying to reinvent the wheel, when companies have already done the wo= rk for you. > Just look at the ST device VNH5019A-E. It will handle easily the 6A RMS y= ou wanted. > I do not know what is your max voltage, but that device is fairly inexpen= sive, like $6 a piece. > > Just my $0.02, > Jean-Paul > AC9GH > > >> On Jan 1, 2015, at 9:21 PM, Neil wrote: >> >> As I read up more on h-bridges, I understand better why you say this >> (about switching time and linear region). I chose 50khz just thinking >> it's well outside the upper audible range) but that's not a critical >> parameter. AIUI, if I drop to 20Khz, the drive requirements get much >> simpler. >> >> However, I just discovered this seemingly neat device -- VNH5019. At >> US$8 with minimal other support components required, is there any reason >> I should really be trying to engineer my own? From what I see of >> discrete-component versions, I'm very much in the same price range alrea= dy. >> >> Cheers, >> -Neil. >> >> >> On 12/17/2014 5:11 AM, IVP wrote: >>>> Usually you don't need vast average gate drive mA - you need >>>> around an amp while the FET is switching but most of the time >>>> the gate does not require current to hold it on or off >>> AIUI the current is needed mostly to charge the gate cap quickly to >>> keep the switching time low (ie keep out of the linear region as much >>> as possible). And once turned on, the FET is voltage, rather than >>> current, driven >>> >>> I PWM a 1/2HP 12V motor with 3 paralleled FETs using a BC337/ >>> BC327 push-pull pair and that works fine, even though the BCs are >>> rated at only 500-800mA. Stall / start current is many times the run >>> current so I do tend to try and remember to soft start >>> >>> Neil, useable speed / torque might not kick in until the PWM is quite >>> high. I think mine is around 30%. Below that the energy simply heats >>> the windings without the motor turning usefully. This may or may not >>> be a problem. For example if there's fan cooling on the shaft >>> >>> My scrollsaw has a *proper* variable-frequency speed control >>> for the induction motor and can be run slowly enough (with good >>> torque, so it's tempting to use it too long) to cause damage if forced >>> cooling isn't used to assist the internal fan >>> >>> Joe >>> >>> >>> ----- >>> No virus found in this message. >>> Checked by AVG - www.avg.com >>> Version: 2015.0.5577 / Virus Database: 4253/8751 - Release Date: 12/17/= 14 >>> >> --=20 >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .