Relay question 1

[monkeysolder]

I would like to use this MOSFET-based relay to switch power on and off to small electronics and have a couple questions. Please let me know if any of this is unclear...

http://www.irf.com/product-info/datasheets/data/pvn012.pdf

1) It shows a 4.5A load current capability but it doesn't appear to have any large pads for heatsinking (gull wing SMT DIP). Should I be concerned about heat at that load?

2) The "C" Connection Diagram on page 3 is stated to handle 4.5A load current. Could I use this as a high-side switch? I am concerend about using a low-side switch as shown because there are other signal paths to the devices that may give a power return even though the power ground is disconnected.

Thanks,

 

[Skogsgurra]

Yes. You should be able to use it as a high-side switch. The isolation is optical and there is a 4 kV specification for input/output isolation. But, the switch voltage is only +/-20 V. You will have to be careful there.

Gunnar Englund

http://www.gke.org

 

[monkeysolder]

Thanks!

 

[itsmoked]

As for the current if your ambient exceeds (WHILE THE CHIP/SYSTEM IS OPERATING AT STEADY-STATE CONDITIONS) 40C then it will not handle the full current rating.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[monkeysolder]

Hmm, so I am a little confused. I understood that N-channel MOSFETs could only sink current so had to be used as low-side switches. As far as I can tell, the two N-channel MOSFETs inside the IC are not connected in any special way except in parallel.

I am definitely using it at the moment as a high-side switch though so could somebody educate me? Thanks,

 

[Skogsgurra]

Since there is an opto-coupler that isolates the control circuit from the switch, it doesn't matter if your switch is high side, low side or even "underground".

Gunnar Englund

http://www.gke.org

 

[monkeysolder]

Neat. So an opto-coupled N-channel MOSFET can be substituted for P-channel MOSFETS in high-side switches. Might be able to save some heat and power with this. Thanks,

 

[monkeysolder]

Substituted with having to worry about producing a gate drive voltage that is 10-15V higher than your positive rail, that is.