Controlled Pulse Generator Example

This example demonstrates a standard time-domain mode where the pulse generator is controlled by IC-CAP. It uses an external signal generator with a scope. IC-CAP directly controls the HP 8130A pulse generator. After loading the 54120.demo.mdl model file, open the mdl8130 model for this example.

In this example, the setup td_meas controls an external signal generator (an HP 8130) that is attached to the DUT and the scope. In this setup, a waveform is acquired on one scope input. Also, IC-CAP exercises the scope's ability to compute period, +width, -width, risetime, falltime, and peak-to-peak voltage.

Measurement/Instrument Setup

The hardware arrangement includes an HP 54123T oscilloscope with an HP 8130A generator. You will need several BNC/APC-3.5 adapters.

A 1 meter, 50-ohm cable is run from the Trigger output of the 8130, onto a 20dB attenuator on the Trigger input of the scope.

A 61cm 50-ohm BNC cable, 8120-1839, is run from the 8130's signal output to a BNC/APC-3.5 adapter connected to scope channel 1 through a 20dB attenuator. Additionally, the signal can be fed to scope channel 1 through the use of a BNC T-connector as described in the 8112 case.

Be sure to issue the Rebuild command so the oscilloscope will be recognized by IC-CAP.

Simulation

The circuit for this model contains a transmission line to simulate the cable run from scope channel 1 to scope channel 4; this helps model the delay that will be apparent in the plotted waveforms. The circuit also contains 50-ohm resistors to simulate the loading offered by the channel 1 input and the channel 4 input. (These resistors would probably be more appropriately represented in a test circuit for the DUT dut_8130.)

Setup specifics

Edit the td_meas setup (mdl8130) as described in the following input and output tables.

Table 113 Inputs

Input Name	Value/Description
time	This input is necessary to specify the time window for which the measured and simulated data will be acquired. It uses the Mode T. Naming it time is not necessary. The start and stop times are selected so that several complete waveforms will be plotted.
ext_pulse	This input describes the pulse stimulus, for simulation purposes. For measurement, you should attempt to key in the same values on the front panel of the pulse generator being used. Note the following comments on some of the important fields. Mode: must be V + Node and - Node: points across which a simulated pulse is applied Unit: must be PULSE1, which corresponds to the output of the 8130. Type: must be PULSE or TDR. PULSE is used in this example. Pulsed Value: 4.0 was the value used to generate the measured data seen in the plot for this setup. Unless you have 20dB attenuators on the scope inputs (a suitable attenuator for 3.5mm connectors is part no. 33340C), this value should be adjusted below 320mv. Rise Time, Fall Time, Pulse Width: Set to 2u, 4u, and 40u for this example. Delay Time, Resistance: Set to 0 for this example. Period: Set to 60u for this example.

Table 114 Outputs

Output Name	Value/Description
wave1	This output will collect a waveform on the 1st input port of the scope. Note the use of CH1 to specify this. The Mode should be '. The simulated waveform is captured across the + and - Nodes shown. A similar wave4 output can be defined to collect a waveform on CH4 of the scope.
period, pwidth, nwidth, risetime, falltime, swing	These outputs are only available for measurement (note the type M) because the oscilloscope computes it using special firmware algorithms. The Mode T is used to request these special Time-domain computations from the scope. By pressing the middle mouse button on the field Pulse Param, you can obtain help (in the Status panel) regarding the choices available from the scope.