Section 13: LPT library function reference Model 4200A-SCS Parameter Analyzer Reference Manual13-142 4200A-901-01 Rev. C / February 2017pulse_fallThis command sets the fall transition time for the pulse output.Usageint pulse_fall(int instr_id, long chan, double fallt);instr_id The instrument identification code of the pulse card, such as VPU1 or VPU2chan Channel number of the pulse card: 1 or 2fallt Pulse fall time in seconds (floating point number):• Fast speed: 10e-9 to 33e-3• Slow speed: 4220-PGU and 4225-PMU: 50e-9 to 33e-3• Default: 100e-9Pulse modesStandardDetailsRise and fall transition time can be set independently for each pulse card channel. There is aminimum slew rate for both the rise and fall transitions. For the fast speed range, the minimum is362 μV/μs, or 1 V/2.7 ms. For the high voltage range, the minimum slew rate is 1.8 mV/μs, or1 V/500 μs. The pulse_range command is used to set pulse speed.As shown below, the pulse fall time occurs between the 100 percent and 0 percent amplitude pointson the falling edge of the pulse, where the amplitude is the difference between the V High and V Lowpulse values.The pulse fall time setting takes effect immediately during continuous pulse output. Otherwise, the falltime setting takes effect when the next trigger is initiated. The pulse_trig command is used totrigger continuous or burst output.For slow speed, note that the minimum transition time for pulse source only (no measurement) on the40 V range is 50 ns for the 4225-PMU and 4220-PGU.Use the pulse_source_timing command to set the pulse fall time for the 4220-PGU and 4225-PMU.
