Kelvin connection

[bk781]

Hello

Why is a kelvin connection needed in IC layout?

-bk

 

[FvM]

It's surely not generally needed but may be used to serve a specific purpose, e.g. separate sense and source connection. Where do you see it?

 

[bk781]

Hi @FvM

In powermosfet high side layout, I have to take kelvin connection from the Source pad and the drain pad to the current sense block. Since it is a current sense block, is it used to sense current or voltage? How does Kelvin connection work?

Thanks
bk

 

[KlausST]

Him

an internet search on "How does Kelvin connection work? " gives 19 million results.
On a first view all results of the first page (explanations, documents, even videos) are very infromative and descriptive.

Are you sure you need a 19.000.000 +1 explanation?


Klaus

 

[timof]

Kelvin connection is useful (or a must have) in situations where you do precision measurements, and your measurement setup may influence the measurement results.

For example, you pass a current through a low-resistance device (a power MOSFET is a very good example, with 1-100 mOhm typical Rdson resistance), and you measure a voltage, to find the resistance R=V/I.
The voltage drop one the leads makes the voltage measurement on device impossible.

So, in Kelvin measurement setup, you use two pairs of probes - one pair is used to pass high (user-defined) current, and you do not care about voltage drop on these leads, and you use another pair or leads/probes (that you place close to the tips of the current forcing leads) to measure the voltage (the current through the sensing leads/probes should be low or zero).

Without a Kelvin setup, measuring resistance in the range below ~100 mOhm is very difficult (if not impossible).

When measuring such low resistance, be sure to eliminate the heating of the device.
Very often, pulsed, quick measurements are used for that.