Hello,

Thank you for reading my question. I am using a P-Channel MOSFET for polarity protection with a circuit using an Arduino Nano.
(A little info about the circuit; the Nano is receiving 9V into the Vin pin and everything else is getting 5V from the 7805).

The MOSFET I'm using is from Tayda, the IRF5305PBF:
Specifications
Series: HEXFET
Transistor Type: MOSFET
Transistor Polarity Channel
Drain Source Voltage(Vds): 55V
Continuous Drain Current(Id): 31A
On Resistance, Rds(on): 60mohm@16A,10V

Which specs are important for a 9V device like mine? Is this part overkill for a 9 Volt device?
I am assuming that Drain Source Voltage(Vds): 55V, and Continuous Drain Current(Id): 31A are the important specs for this kind of use as a low voltage polarity protection?

I'm just learning about this part, not sure what to make of the specs.
Sincere thanks for any advice,
Tony Am

 

Which specs are important for a 9V device like mine? Is this part overkill for a 9 Volt device?

Voltage and current. Overkill but it will work

 

I advise you to put a 100K resistor in the gate and plug the Gate Source with a 0.1UF capacitor. This will limit the maximum pulse current generated by charging the capacitors. I advise you to model the scheme.

 

Voltage and current. Overkill but it will work

Hello, thank you. I was wondering if you could help me understand the P-Channel MOSFET being used this way. The Voltage and current are the important specs, am I correct in assuming that I could use a part with even higher V & I rating, however a MOSFET with a lower V & I rating (lower than the operating current and Voltage of my circuit) would not work?
Thanks again,
TonyAm

 

I advise you to put a 100K resistor in the gate and plug the Gate Source with a 0.1UF capacitor. This will limit the maximum pulse current generated by charging the capacitors. I advise you to model the scheme.

Thank you for your help.

 

am I correct in assuming that I could use a part with even higher V & I rating, however a MOSFET with a lower V & I rating (lower than the operating current and Voltage of my circuit) would not work?

That's basically true, but not complete.

You want the voltage rating to be greater than the likely reverse voltage that could be applied to the circuit.

And it's not just the current rating that's important.
You want the on-resistance of the MOSFET (from the data sheet) to provide a negligible IR voltage drop due to the normal circuit operating current.

 

That's basically true, but not complete.

You want the voltage rating to be greater than the likely reverse voltage that could be applied to the circuit.

And it's not just the current rating that's important.
You want the on-resistance of the MOSFET (from the data sheet) to provide a negligible IR voltage drop due to the normal circuit operating current.

Great, thanks very much.
TonyAm

 

I'm looking for a P-Channel MOSFET, smd type for having JLCPCB assemble for me on my PCB, any recommendations for a 9V, approx 1A circuit (as above)?

 

Hello, thank you. I was wondering if you could help me understand the P-Channel MOSFET being used this way. The Voltage and current are the important specs, am I correct in assuming that I could use a part with even higher V & I rating, however a MOSFET with a lower V & I rating (lower than the operating current and Voltage of my circuit) would not work?
Thanks again,
TonyAm

The advantage is a very low loss of voltage through the mosfet compared to using a ordinary diode which may be important depending on the application

 

I'm looking for a P-Channel MOSFET, smd type for having JLCPCB assemble for me on my PCB, any recommendations for a 9V, approx 1A circuit (as above)?

AN3401

 

I'm looking at:
https://www.lcsc.com/product-detail/MOSFETs_Winsok-Semicon-Winsok-Semicon-WST3407_C105163.html
https://www.lcsc.com/product-detail/MOSFETs_Wuxi-NCE-Power-Semiconductor-NCE60P04Y_C102608.html

 

Even better.

 

AN3401

This: https://www.lcsc.com/product-detail/MOSFETs_YFW-AO3401_C2977510.html?s_z=n_AN3401

 

Correct the AO3401.

 

Correct the AO3401.

Great, thanks very much. In case anyone else would like to use this parts, it's C2977510 on LCSC

 

Now I'm looking for a SOT (smd) version of the 7805, voltage regulator. Any advice would be greatly appreciated.

Sincere thanks,
TonyAm

 

For a suitable 5V voltage regulator I am looking at:
https://www.lcsc.com/product-detail/Voltage-Regulators---Linear,-Low-Drop-Out-LDO-Regulators_Diodes-Incorporated-Diodes-Incorporated-AS7805ADTR-E1_C127926.html

Should I go with an output I of 1A, or 1.5A? The Through hole 7805 I have been using has an output I of 1.5A

 

That chip will maintain regulation as long as the input voltage is 7 volts or higher.

 

That chip will maintain regulation as long as the input voltage is 7 volts or higher.

Great, thanks again.

 

See