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Choosing the appropriate wire to board connector

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slayer2211

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Hi all,

I am designing PCB for power distribution. Basically the board will be connected to two power supplies and it will distribute power to multiple circuit/module through multiple connectors. I am having a hard time in understanding how the current rating of a connector works. I do know that lot of factors are involved in determining the max current such as size of AWG wire used, pcb traces width, ambient and rise temperature.

For example the XA connector from JST manufacturer is rated as below:
Voltage Rating: 250 V AC DC
Current Rating: 3 A AC DC (AWG 22,20)

Now let say I am going to select a 4-way/circuit connector. Does it mean the 3A is the max current allowed for each pin or does 3A has to be the sum of current that goes through every pin powered simultaneously?

Also I am planning to use the 4 way connector to connect power up 2 modules, that will deliver 2A current on each module, and the configuration will look something like PWR, GND, GND, PWR for pin 1,2,3,4 respectively. Do I have to count the Ground as current carrying wire? That being said, I would like to know if total current would be listed as 4A (2+2) or 8A (2+2+2+2).

Thanks
 

andre_teprom

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Some manufacturers of connectors explicitly disapprove distribute among various pins a current above the limit rated for each pin. This much probably is settled just for avoid that a pin is subjected to the risk to carry a current that exceeds the limit specified for each one, during a hot swap, due the fact that at this event could occur an instantaneous unbalanced contact between pins of both male and female connectors.

I already did that anyway, but oversizing the number for a comfortable amount much above the mere sum of equally distributed values.

the configuration will look something like PWR, GND, GND, PWR for pin 1,2,3,4 respectively
In general, I prefer to place the GND net at the corners of connectors, because such an arrangement ensures that during hot plugging, the equipment will be never electrically energised prior to the ground reference ( note that connector often is plugged aside first ).
 

slayer2211

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Some manufacturers of connectors explicitly disapprove distribute among various pins a current above the limit rated for each pin. This much probably is settled just for avoid that a pin is subjected to the risk to carry a current that exceeds the limit specified for each one, during a hot swap, due the fact that at this event could occur an instantaneous unbalanced contact between pins of both male and female connectors.
So if the connector is rated at 3A, it actually refers to the current limit for EACH pin? And if I were to distribute the current through all pins, the sum has to be lower (plus derating factor) than 3A?

What about the the putting the PWR and GND pair in a same connector. If it delivers 2A to the circuit, would that make the total current in a connector to be 4A? (considering that 2A also flows through the GND)

Thank you
 

andre_teprom

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What about the the putting the PWR and GND pair in a same connector.
As a matter of signal integrity as well as to reduce the possibility of EMI interference, it is always a good practice to keep the reference and power signal wired together at the same connector, thus preventing the opening of spinning rings which could be a source of transmission or capture of noise.

If it delivers 2A to the circuit, would that make the total current in a connector to be 4A? (considering that 2A also flows through the GND)
The same current flowing at the connector will come out, and thus you cannot add, and the specification for connector is 2A. The connectors that I have experienced refer to the current limit rated for each pin, not the whole connector - note that the connecting of the same signal at different pins is not necessarily always expected, although very common.

Can you share the link of the connector that you are referring ?
 

andre_teprom

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Does it mean the 3A is the max current allowed for each pin or does 3A has to be the sum of current that goes through every pin powered simultaneously?
According to datasheet, each pin of this connector can handle up to 3A DC.
If you select a model with 4 pins, gathering GND and Power in pairs, the maximum allowable is 6A.
 

asdf44

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Current ratings are typically per pin.

But, often the current will de-rate if you're using every pin to carry current (for obvious heat reasons). Power connectors in particular will often specify this. So always take a look for this.
 

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