# JESD78D - pin clamping voltage and current

I'm studying the JEDEC Standard No. 78D and on one of its notes it says: "The pin clamping voltage for positive I-test is given by Vclamp = Vmax + 0.5(Vmax-Vmin) with an upper limit of 1.5Vmax..."

What does it mean with "pin clamping voltage"?

In another part of the text it states: "The current clamp for the supply group is set according to the total nominal supply current of the group. The clamp current for the Jth supply group is the greater of a or b..."

What does "current clamp" mean?

• Are you able to reproduce the text from the JEDEC standard so we can see it in-context? Maybe you can give a link to it? Jul 6, 2013 at 22:02
• Andy, here is a link so you can download the complete standard in pdf, it's only 208KB :dl.dropboxusercontent.com/u/71208870/… Jul 6, 2013 at 22:10

CMOS circuit latchup (for example) is explained here. The purpose of the JEDEC document specified is to test a particular device to see if it is vulnerable to latchup. It does this by (in simple words) testing at 1.5 x the supply voltage on inputs and outputs. This is the pin clamping voltage.

Voltage latch-up testing forces a voltage onto pins to see if CMOS latchup takes place. This can also be tested by injecting a current so "current clamp" is an alternative test using a current injection limited to the value in the document.

Hope this makes sense.

• I'm sorry, but I still don't understand what clamping voltage is. It seems that there is a relation between the current used for the test (I-test) and the "clamping voltage". Please take a look at Table 2 on page 7 of the standard (footnotes 2, 3 and 4). Jul 7, 2013 at 12:44
• I believe the term "clamping" means the voltage at which SCR clamping may take place. It doesn't mean that "clamps" will occur at that voltage. Jul 7, 2013 at 13:40
• I finally understood what clamping means in this document. Clamp = limit. For a certain current test you must limit the maximum voltage (pin clamping voltage) that the generator will supply to avoid the destruction of the device. Jul 7, 2013 at 15:39