choosing a reverse protection diode

[anishkgt]

hi All,

I have a Constant current source used for powering a servo 7v 3A and wish to protect it against reverse polarity. What would be the specs that i should be looking for.

I went though DigiKey and if am not wrong are standard rectifier ideal for this application ?

Thanks in advance.

[Signal32]

You probably don't want to use a diode with such high currents, you will loose a lot of power and generate a lots of heat in the diode.
Use a MOSFET: http://www.ti.com/lit/an/slva139/slva139.pdf

[David Hess]

If the reverse voltage is moderate, then a schottky rectifier will have about half of the loss making it more acceptable.  Even with significantly derating, a schottky rectifier will be inexpensive.

[anishkgt]

So would something like a schottky above 3A be ok say about 5A ?


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[David Hess]

So would something like a schottky above 3A be ok say about 5A?

I do not quite understand what you are asking.  The average and peak current ratings for the diode should exceed the average and peak currents that you expect in the circuit.  This should not be a problem as currents higher than 5 amps are available inexpensively even in small packages.

[anishkgt]

The stall amp of the servo is 3A and normal working is 1 to 1.5A. So I guess 5A has enough room.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[anishkgt]

Secondly can these be placed on the negative side also or should it be in positive voltage to the load.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

[David Hess]

Secondly can these be placed on the negative side also or should it be in positive voltage to the load.

That depends on the signaling requirements and whether a positive or negative signal common is used.  Vehicles for instance use a negative ground so reverse protection goes on the positive side.

[anishkgt]

Thank you David. The servo is controlled via an arduino for a project and the GND is common. Here i am using the Constant Current source which needs to protect by the diode agains reverse polarity.