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Mosfet Drivers and Input Hysteresis

D

D from BC

Jan 1, 1970
0
Isn't this a kickass mosfet driver?
http://ixdev.ixys.com/DataSheet/99061.pdf
IXYS ISDD414PI

Anyways...as on the datasheet..
Vih=3.5min
Vil = 0.8Vmax..
That just tells me the max hysteresis...
The min hysteresis is unknown and the typical input hysteresis is
unknown.
Heck..I'm not even sure if chip has input hysteresis.. :p
(I sent an email to IXYS Corp but it's the weekend...)

I've noticed some Microchip drivers have 300mV input hysteresis..
The max5048 has a whopping 1.6V of input hysteresis but no stock at
Digikey..

I want to put a slooooowwwww signal + some noise to a mosfet driver.
Anybody know a mosfet driver that has something between 0.5V to 1V of
input hysteresis?

I suspect this is going to be a pita item to search for because input
hysteresis is too "mickey mouse" to include on manufacturers selection
tables..
This means looking at every freakn datasheet...?
Or should I just email a bunch of companies for the info?
D from BC
 
J

Joerg

Jan 1, 1970
0
D said:
Isn't this a kickass mosfet driver?
http://ixdev.ixys.com/DataSheet/99061.pdf
IXYS ISDD414PI

Anyways...as on the datasheet..
Vih=3.5min
Vil = 0.8Vmax..
That just tells me the max hysteresis...
The min hysteresis is unknown and the typical input hysteresis is
unknown.
Heck..I'm not even sure if chip has input hysteresis.. :p
(I sent an email to IXYS Corp but it's the weekend...)

I've noticed some Microchip drivers have 300mV input hysteresis..
The max5048 has a whopping 1.6V of input hysteresis but no stock at
Digikey..

I want to put a slooooowwwww signal + some noise to a mosfet driver.
Anybody know a mosfet driver that has something between 0.5V to 1V of
input hysteresis?

I suspect this is going to be a pita item to search for because input
hysteresis is too "mickey mouse" to include on manufacturers selection
tables..
This means looking at every freakn datasheet...?
Or should I just email a bunch of companies for the info?
D from BC


It's customary to provide your own hysteresis ;-)

Seriously, a couple of resistors do the trick. Or drive the driver with
with Schmitt.
 
D

D from BC

Jan 1, 1970
0
It's customary to provide your own hysteresis ;-)

Seriously, a couple of resistors do the trick. Or drive the driver with
with Schmitt.

Yeah...but I'm trying to reduce the component count.. I make my own
PCB's so if my circuits are low in components then I don't have to do
much PCB drafting and fab..
D from BC
 
R

Robert Adsett

Jan 1, 1970
0
D from BC said:
Isn't this a kickass mosfet driver?
http://ixdev.ixys.com/DataSheet/99061.pdf
IXYS ISDD414PI

Anyways...as on the datasheet..
Vih=3.5min
Vil = 0.8Vmax..
That just tells me the max hysteresis...
The min hysteresis is unknown and the typical input hysteresis is
unknown.
Heck..I'm not even sure if chip has input hysteresis.. :p
(I sent an email to IXYS Corp but it's the weekend...)

I've noticed some Microchip drivers have 300mV input hysteresis..
The max5048 has a whopping 1.6V of input hysteresis but no stock at
Digikey..

I want to put a slooooowwwww signal + some noise to a mosfet driver.
Anybody know a mosfet driver that has something between 0.5V to 1V of
input hysteresis?

Or just spring for a Schmitt trigger input buffer (or build one).

Robert
 
D

D from BC

Jan 1, 1970
0
Or just spring for a Schmitt trigger input buffer (or build one).

Robert

It might end up doing that if I have a favorite mosfet driver and I
don't like it's input hysteresis :(
I know many ways to create hysteretic circuits...I just don't want to
include one.. :)
D from BC
 
J

Joerg

Jan 1, 1970
0
D said:
Yeah...but I'm trying to reduce the component count.. I make my own
PCB's so if my circuits are low in components then I don't have to do
much PCB drafting and fab..
D from BC


But then you'll be stuck with expensive boutique parts that hardly
anybody else uses.
 
L

legg

Jan 1, 1970
0
Yeah...but I'm trying to reduce the component count.. I make my own
PCB's so if my circuits are low in components then I don't have to do
much PCB drafting and fab..

Make it work first. This is the wrong place to introduce a high
impedance node.

RL
 
D

D from BC

Jan 1, 1970
0
Make it work first. This is the wrong place to introduce a high
impedance node.

RL

The mosfet driver IC input will get a slow non square signal but it'll
be from a relatively low impedance source.
The input shouldn't flap around in the wind so to speak..
But I'll check to see if anything else will kick the mosfet driver
input.
D from BC
 
D

D from BC

Jan 1, 1970
0
But then you'll be stuck with expensive boutique parts that hardly
anybody else uses.

Ahh.. but if the boutique parts speed up my project time..great!
As long as the boutique parts stay at a insignificant cost level..
Ex..I change $900.00 for a one off project.. One $4.00 boutique part
is insignificant..
D from BC
 
L

legg

Jan 1, 1970
0
The mosfet driver IC input will get a slow non square signal but it'll
be from a relatively low impedance source.
The input shouldn't flap around in the wind so to speak..
But I'll check to see if anything else will kick the mosfet driver

Turn the source into a comparator with hysterisis. This is the wrong
place in the circuit to decide whether or not you want to switch. The
decision should already have been made.

Even under those conditions, you'll see drivers with hysterisis equal
to 30% of the input logic supply rail - and for good reasons.

RL
 
J

Joerg

Jan 1, 1970
0
D said:
Ahh.. but if the boutique parts speed up my project time..great!
As long as the boutique parts stay at a insignificant cost level..
Ex..I change $900.00 for a one off project.. One $4.00 boutique part
is insignificant..


Ok then. As long as they don't have to build another one in three years
and then your part has gone unobtanium.
 
D

D from BC

Jan 1, 1970
0
Ok then. As long as they don't have to build another one in three years
and then your part has gone unobtanium.

Yeah..that's the risk...
It could be good for business.. :p
I just say
"It's not my fault Supertex discontinued the part."
I can make a new design with another part.. but that'll be another
$900.00 :)
Isn't that just evil :)

I do recall on one design where I couldn't find a boutique part, did
it the long way, did the pcb and then found a boutique part..
Damn..
So.I kept the original PCB artwork and merged in the artwork for the
boutique part..
So...if the boutique part got discontinued..the artwork exists for the
fatter equivalent circuit.
Then I turned the situation into a selling point.."Discontinued part
resistant design". :)
D from BC
 
J

Joerg

Jan 1, 1970
0
D said:
Yeah..that's the risk...
It could be good for business.. :p
I just say
"It's not my fault Supertex discontinued the part."
I can make a new design with another part.. but that'll be another
$900.00 :)
Isn't that just evil :)

Problem is, some day word gets around. Clients don't like that ;-)

I do recall on one design where I couldn't find a boutique part, did
it the long way, did the pcb and then found a boutique part..
Damn..
So.I kept the original PCB artwork and merged in the artwork for the
boutique part..
So...if the boutique part got discontinued..the artwork exists for the
fatter equivalent circuit.
Then I turned the situation into a selling point.."Discontinued part
resistant design". :)


That's what my clients expect (and get) with every design...
 
J

John Devereux

Jan 1, 1970
0
Problem is, some day word gets around. Clients don't like that ;-)




That's what my clients expect (and get) with every design...

Another thing is that driver pushes 14 amps! Better watch that
bypassing...
 
W

whit3rd

Jan 1, 1970
0
I know many ways to create hysteretic circuits...I just don't want to
include one.. :)

An easy one would be a low-voltage '555. Hysteresis from
1/3 V to 2/3 V, good logic-switch output, doesn't need any external
passives.
 
D

D from BC

Jan 1, 1970
0
An easy one would be a low-voltage '555. Hysteresis from
1/3 V to 2/3 V, good logic-switch output, doesn't need any external
passives.

It's a favorite technique..but it's still an extra part that I think I
can avoid it if I chose the right mosfet driver having about 1V of
input hysteresis.
I've haven't received an email from IXYS yet..

I want a new 555 :)
I want 2 high speed internal comparators (nS) rail to rail with no
ties to internal resistors.
Something like what Analog devices has...
And..
I want 1 fast internal RS latch.
Maybe 5V HC type.
And...Bonus if I can get a 1A push pull drive output up to 16V.
Call it the Super555 :)
D from BC
 
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