Hi Richard.

Sorry I wasn't clear. I'll try again.

I totally agree with your statements about measuring the output characteristics. But they produce the same results that I got.

A given output buffer will have an I-V curve that is fixed with a given process, temperature, and supply voltage. To a first order approximation, it doesn't really matter where on the curve you measure it, since one point defines it.

Consider a 10 ohm resistor. Force 1 volt and measure 100mA. Force 2 volts and measure 200 mA. Force 30 mA and measure 0.3 volt. Three different measurement techniques and all resulted in the same 10 ohm measurement.

I didn't try it on the Intersil part, but if I forced the part to source 2.5 mA, I would have measured 4.9 V. And if I had increased the load current until the Voh fell to 3.7 volts, I would measure a current of about 32 mA.

These are all just other points on the same curve, and confirm that the P-channel transistor looked like a 40 ohm resistor.

However, on the production test floor, all measurement points are not the same. There are arguments against high current measurements on chips. Measuring a 32 mA Ioh at 3.7 volts dissipates about 40mW of power in a really small area. The output transistor will heat up and become weaker, thus affecting this measurement and all subsequent measurements.

Also, higher test currents can cause all sorts of secondary problems. You can get IR drops and noise coupling in the cable connecting the tester to the handler. You can also inadvertently exceed the current limits in the tester power supplies.

--------

I was referring to the NC pins on the 44 pin packages for possible additional power supplies. You are stuck with 2 supplies on the 40 pin DIP.