I expected to see a simple pattern of increasing power and decreasing resistance but this wasn’t the case. These connectors have resistances ranging from the extremely low 0.15 milliohms, like in the Zpower series, to 20 milliohms, in the PowerPlus signal contacts, and support voltages and currents up to 600V and 50A respectively. I grabbed data for a handful of Molex connectors mostly looking at their range of power connectors like the EXTreme, Sabre, and Mini-Fit series. Now that we have looked at a couple of the impacts of resistance in connectors we can line up a couple of them and see how they stack up. In audio output the ideal impedance arrangement is for the amplifier impedance to be less than the speaker impedance so your connectors need to be low resistance not to impact this relationship.
A lot of times the RF systems are based on a 50 ohm specification. In RF connectors you want your transmitter output impedance to be matched to the antenna impedance as closely as possible which allows for maximum power output. So I have said all these bad things about connector resistance but there are a few areas where controlled connector resistance is desirable, antenna matching and audio output being the first ones that spring to mind. Another impact of this power loss to heat is that the connector itself heats up and connectors tend to derate with increased temperature meaning your system stability may be compromised by a hot connector. One downside of this is that the efficiency of the system goes down, the worst one I have seen is 1/10 of a percent power loss at the connector and when working on a system that is pushing for the highest efficiency possible a tenth of a percent is a decent chunk. The next element that gets noticed is heat or power loss, as you push current through a resistive element there will be some power lost to heat and the more resistive that element the more power you burn off. In high voltage connectors, say 600V, 2/10 of a volt will probably get lost in your ripple voltage.
If you are working on low voltage systems like FPGAs and microprocessor that utilize very high currents and happen to run at 3.3V or lower 2/10 of a volt is something you really have to pay attention to. Like any resistor in a system you end up with a voltage differential across is as current is pushed through it, in some cases at high currents there can be drops of up to 2/10 of a volt which in the grand scheme of things isn’t a huge amount. So what happens as resistance shows up in our connection points? The first one that will be noticed is probably voltage drop.
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