"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 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
Well, 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
Reply by Chris Carlen●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 Dejan Durdenic●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 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
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 Earl Bollinger●March 24, 20042004-03-24
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/