Using Low side drivers with high side P-Mos transistors
Hi,
In a half bridge configuration what would prevent using Low side Mosfet
drivers with P-Mos transistors placed on the high side ?
A 12V power supply is used and in that case the Gate-Source voltage will always stay below the usual 20V maximum.
Thanks in advance for any help
Can't think of anything that would stop you...
Using Low side drivers with high side P-Mos transistors
Thanks for your response. Looks like the response was obvious but I am notOriginally Posted by dknguyen
very comfortable with analog stuff.
Just for confirmation is the following (simplified) schematic correct ?
http://cjoint.com/?ihqeZK5nFH
Which means that with a quad low-side driver I can drive a full bridge with
2 P-Mos at the top and 2 N-Mos at the bottom ?
Just for curiosity what if the bridge power supply was above 20V ?
Looks right. Not sure what you are using it for but you want fast-recovery or schotky diodes in reverse-parallel with the MOSFET source-drain to protect them from inductive flyback if you are switching an inductive load.
That would work.
If the supply is above 24V, then you need to take the p-channel MOSFETS to 24V to turn them off and not below 4V to turn them on.
I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.
Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.
Ah, yeah, the motor voltage has to be equal to or less than the gate-drive voltage so you can turn the PMOS off.
By the way I wonder why "Low Side" drivers are called this way as they look pretty generic. This was a little confusing to me.
On the other side "High Side" drivers are very specific as they contain a charge pump and are designed for N-Mos devices placed at the top.
Low-side to me means the transistor is stuck "low" to ground. And high-side means the transistor is stuck "high" to +V.
Yes but I was refering to high or low side drivers not transistors.
And in that case the symetry does not apply to drivers.
the gate thresholds would cause both fets to be partially on during crossover unless appropriate isolated gate drivers are used.....a high side PNP bipolar transistor can be used with an N Mos transistor to ground with base and gate tied together
Last edited by joecioppi; 30th June 2009 at 05:05 AM.
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