I am using the TC4427 MOSFET driver IC to generate some high voltages like Microchip's Appnote details here. The problem is according the the data sheet Vdd can be up to a max of 18v. If I apply anything much over 5v, the current draw goes over 1.5 amps and the chip dies almost instantly. I even took one IC and grounded the two inputs and left the outputs open and at 12v, the IC drew 1.8 amps and cooked itself in a split second. Those little SOIC chips burn quick. I beleive that the TC4427 (and it's like chips too) that Vdd is actually 5v to maybe 5.5v max and that the outputs are tolerant up to a max of 18v. unlike what the data sheet states. Unless I just can't read anymore. Anyway, I duplicated the circuit to generate high voltage like in th appnote. And the design does work quite well. But the LRF620 power MOSFET runs pretty hot. So I thought that running the TC4427 at 5 volts wasn't driving the IRF620's gate hard enough leaving it in the analog range, thus causing the heat build up. But my surprise was the TC4427 didn't like 12v at all. Even though the half bridge output on the TC4427 would imply you cannot turn on both the high and low side drivers at the same time, that the TTL level shifter inside the TC4427 is what is acting like it is shorting out. I guess it isn't all that big of a deal, I could always run a bigger heatsink. Or maybe a better MOSFET with a lower RDS. Or even switch the TC4427 out for a IR2104 half bridge driver and only run the high side MOSFET. Has anyone else run into this situation with the TC4427 or knows what I did wrong or something about it? Have a soda on me. Thanks Earl Referencing the appnote from Microchip http://www.microchip.com/download/appnote/pic16/91053a.pdf For the TC4427 Mosfet driver. Data sheets http://www.microchip.com/1010/pline/analog/anicateg/power/mosfet/tc4_46/tc4427/
Using the TC4427 MOSFET driver IC is the data sheet in error? Or is it me?
Started by ●March 24, 2004
Reply by ●March 25, 20042004-03-25
"Earl Bollinger" <earlwbollinger@comcast.net> wrote in message news:HNadnbE7xaeC2f_dRVn-hw@comcast.com...> I am using the TC4427 MOSFET driver IC to generate some high voltages like > Microchip's Appnote details here. > The problem is according the the data sheet Vdd can be up to a max of 18v. > If I apply anything much over 5v, the current draw goes over 1.5 amps and > the chip dies almost instantly. I even took one IC and grounded the two > inputs and left the outputs open and at 12v, the IC drew 1.8 amps andcooked> itself in a split second. Those little SOIC chips burn quick. > I beleive that the TC4427 (and it's like chips too) that Vdd is actually5v> to maybe 5.5v max and that the outputs are tolerant up to a max of 18v. > unlike what the data sheet states. Unless I just can't read anymore. > Anyway, I duplicated the circuit to generate high voltage like in th > appnote. And the design does work quite well. But the LRF620 power MOSFET > runs pretty hot. So I thought that running the TC4427 at 5 volts wasn't > driving the IRF620's gate hard enough leaving it in the analog range, thus > causing the heat build up. But my surprise was the TC4427 didn't like 12vat> all. Even though the half bridge output on the TC4427 would imply youcannot> turn on both the high and low side drivers at the same time, that the TTL > level shifter inside the TC4427 is what is acting like it is shorting out. > I guess it isn't all that big of a deal, I could always run a bigger > heatsink. Or maybe a better MOSFET with a lower RDS. Or even switch the > TC4427 out for a IR2104 half bridge driver and only run the high side > MOSFET. > > Has anyone else run into this situation with the TC4427 or knows what Idid> wrong or something about it? > Have a soda on me. > Thanks > Earl > Referencing the appnote from Microchip > http://www.microchip.com/download/appnote/pic16/91053a.pdf > > For the TC4427 Mosfet driver. > > Data sheets >http://www.microchip.com/1010/pline/analog/anicateg/power/mosfet/tc4_46/tc4427/> >I cannot speak for TC4427, howewer I 'm using TC4420, -21, -22 and -29 - with +15V supply and all of them without any problems... You can avoid MOSFET driver in your application by selecting a MOSFET that has 5V gate threshold. Those can be found (eg. BUZ11L)... PIC will happily saturate such a device. There's another point abuot that app.note - as the driver is of non-inverting type, after reset MOSFET is always turned on, posing a short circuit to ground until CPU starts...It would be safer to modify the code and insert inverter between MOSFET gate and PIC output... regards Dejan
Reply by ●March 25, 20042004-03-25
Earl Bollinger wrote:> I am using the TC4427 MOSFET driver IC to generate some high voltages like > Microchip's Appnote details here. > The problem is according the the data sheet Vdd can be up to a max of 18v. > If I apply anything much over 5v, the current draw goes over 1.5 amps and > the chip dies almost instantly. I even took one IC and grounded the two > inputs and left the outputs open and at 12v, the IC drew 1.8 amps and cooked > itself in a split second. Those little SOIC chips burn quick. > I beleive that the TC4427 (and it's like chips too) that Vdd is actually 5v > to maybe 5.5v max and that the outputs are tolerant up to a max of 18v. > unlike what the data sheet states. Unless I just can't read anymore. > Anyway, I duplicated the circuit to generate high voltage like in th > appnote. And the design does work quite well. But the LRF620 power MOSFET > runs pretty hot. So I thought that running the TC4427 at 5 volts wasn't > driving the IRF620's gate hard enough leaving it in the analog range, thus > causing the heat build up. But my surprise was the TC4427 didn't like 12v at > all. Even though the half bridge output on the TC4427 would imply you cannot > turn on both the high and low side drivers at the same time, that the TTL > level shifter inside the TC4427 is what is acting like it is shorting out. > I guess it isn't all that big of a deal, I could always run a bigger > heatsink. Or maybe a better MOSFET with a lower RDS. Or even switch the > TC4427 out for a IR2104 half bridge driver and only run the high side > MOSFET. > > Has anyone else run into this situation with the TC4427 or knows what I did > wrong or something about it? > Have a soda on me. > Thanks > Earl > Referencing the appnote from Microchip > http://www.microchip.com/download/appnote/pic16/91053a.pdf > > For the TC4427 Mosfet driver. > > Data sheets > http://www.microchip.com/1010/pline/analog/anicateg/power/mosfet/tc4_46/tc4427/Hi: I use this device alot, mostly just with 5V. Just to check on your problem I just wired the device (DIP8, not SOIC) to +15V, fed a square wave of 0-5V to the inputs (paralleled inputs), and drove a 100 ohm resistor in parallel with 1000pF cap to ground with the paralleled outputs. The device has no difficulties. I also have a 0.1uF ceramic bypass across the power pins and very close to the package. I also have some things with the SOIC versions installed and working fine. You either have a bad batch of chips or you have overlooked a wiring error. Don't feel bad, it happens. Good luck! -- ____________________________________ Christopher R. Carlen Principal Laser/Optical Technologist Sandia National Laboratories CA USA crcarle@sandia.gov
Reply by ●March 25, 20042004-03-25
"Chris Carlen" <crcarle@BOGUS.sandia.gov> wrote in message news:c3vmhq03au@enews3.newsguy.com...> Hi: > I use this device alot, mostly just with 5V. Just to check on your > problem I just wired the device (DIP8, not SOIC) to +15V, fed a square > wave of 0-5V to the inputs (paralleled inputs), and drove a 100 ohm > resistor in parallel with 1000pF cap to ground with the paralleledoutputs.> The device has no difficulties. I also have a 0.1uF ceramic bypass > across the power pins and very close to the package. > I also have some things with the SOIC versions installed and working > fine. You either have a bad batch of chips or you have overlooked a > wiring error. Don't feel bad, it happens. > Good luck! > Christopher R. Carlen > Principal Laser/Optical Technologist > Sandia National Laboratories CA USA > crcarle@sandia.govWell, I guess these are some sort of bad batch of chips or something. Bummer, now I won't be using these chips on anything again. With only 8 pins it's hard to make wiring errors, but I triple checked to be on the safe side. They work at 5v but short out at 12v. Maybe someone changed the specs with a new rev step level of IC. I am going to change out the circuit to use a IR2117 high side Mosfet driver. I know they work at 12v no problem. It'll be interesting to see if it solves the problem with the IR620 needing a big heat sink. it would be nice to get it down to a D2pack MOSFET with a copper pad for a small heat sink. Thanks Earl
