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H-Bridge with level shift - MOSFET gate voltage issues?

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Joe Chisolm
Guest

Tue Jan 08, 2019 5:45 am   



On Tue, 08 Jan 2019 00:05:31 +0100, Piotr Wyderski wrote:

Quote:
Lasse Langwadt Christensen wrote:

https://www.allegromicro.com/~/media/Files/Datasheets/A4950-Datasheet.ashx

Now this is something very close to my needs, thanks!

Best regards, Piotr


I gave you a TI part, DRV8871, .565ohm rds, 45 v, 3.5a and you can get a
breakout board from adafruit for $7.50USD

https://www.adafruit.com/product/3190


--
Chisolm
Republic of Texas


Guest

Tue Jan 08, 2019 6:45 am   



On Tuesday, January 8, 2019 at 2:48:01 PM UTC+11, k...@notreal.com wrote:
Quote:
On Mon, 7 Jan 2019 09:46:34 -0800 (PST), makolber_at_yahoo.com wrote:



No, but I am considering that the 1000th harmonic of a square wave has
pretty low amplitude. The math is well documented.

But neglecting the fact that AM radio signal with which that harmonic would interfere also has a pretty low amplitude.


the 60 Hz harmonics of a standard lamp dimmer certainly can and DO interfere with AM radio.

But in this case the RFI isn't harmonics of 60Hz. It's harmonics of
the parasitic elements of the switching circuit.


"Parasitics elements " don't have harmonics, frequencies do.

In this case the PWM waveform is nominally a square wave which has odd harmonics whose amplitudes decline in proportion to the harmonic number. If the square starts off faster than 60Hz, the harmonics are going to bigger.

--
Bill Sloman, Sydney

Piotr Wyderski
Guest

Tue Jan 08, 2019 10:45 pm   



Hi Joe,

Joe Chisolm wrote:

Quote:
I gave you a TI part, DRV8871, .565ohm rds, 45 v, 3.5a and you can get a
breakout board from adafruit for $7.50USD


Thanks, indeed a very interesting part. But I don't see your other
posting where you gave it to me. On my end this is the first message
from you.

Best regards, Piotr

Joe Chisolm
Guest

Tue Jan 08, 2019 11:45 pm   



On Tue, 08 Jan 2019 22:11:00 +0100, Piotr Wyderski wrote:

Quote:
Hi Joe,

Joe Chisolm wrote:

I gave you a TI part, DRV8871, .565ohm rds, 45 v, 3.5a and you can get a
breakout board from adafruit for $7.50USD

Thanks, indeed a very interesting part. But I don't see your other
posting where you gave it to me. On my end this is the first message
from you.

Best regards, Piotr


easy to get lost in all the post. pardon my tying mistakes. sliced
my finger before the holidays so i'm still one handed typing
for a while.

If you are still thinking about rolling your own, the FDC5614P is
a logic level P. 60V, 3A, Vgs -1.6 NTF3055L108 - logic level N channel
60V 3 A Drive them from gpio pins on the Pi.
dont remember if the PI gpio has pull up or down. watch for that
on the gate drive.


--
Chisolm
Republic of Texas

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