3350F Series Operation Manual 7
The load current level and load status are can be set with Front panel on each module, GPIB
command. It is called manual operation and GPIB operation respectively, the load input
voltage and load current can be read back to computer through GPIB.
The GPIB operation is described in Chapter 4 GPIB operation.
Slew Rate:
Slew rate is defined as the change in current or voltage over time. A programmable slew rate
allows a controlled transition from one load setting to another to minimize induced voltage
drops on inductive power wiring, or to control induced transients on a test device (such as
would occur during power supply transient response testing).
In cases where the transition from one setting to another is large, the actual transition time can
be Calculated by dividing the voltage or current transition by the slew rate. The actual transition
time is Defined as the time required for the input to change from 10% to 90% or from 90% to
10% of the Programmed excursion. In cases where the transition from one setting to another is
small, the small Signal bandwidth of the load limits the minimum transition time for all
programmable slew rates. Because Of this limitation, the actual transition time is longer than
the expected time based on the slew rate, as Shown in Figure 1-12
Therefore, both minimum transition time and slew rate must be considered when determining
the actual transition time.
The minimum transition time for a given slew rate as about a 30% or greater load change, the
slew rate increases from the minimum transition time to the Maximum transition time at a 100%
load change. The actual transition time will be either the minimum transition time, or the total
slew time (transition divided by slew rate), whichever is longer.
Use the following formula to calculate the minimum transition time for a given slew rate
Min transition time = 36/slew rate (in amps/second)(7.2us(36/5)*0.8(10%~90%)=5.76uS)
Use the following formula to calculate the maximum transition time for a given slew rate
Max transition time = 120/slew rate (in amps/second) (24us(120/5)*0.8(10%~90%)=19.2uS)
EX. CCH=24A, CCL=0A Slew Rate = 5A, The expected time is 3.84uS but the actual transition
time will be limited to 5.76uS((36/5)x0.8 )
