User Connections
66
Be careful of capacitive coupling from the programming inputs to other lines wired to the analog connector. Such coupling
can cause output oscillations. You can minimize coupling by bundling the IP, VP, and Common P lines and keeping them
separated from other wires. Twisting these three lines together is also recommended.
Analog connector
l=Voltage programming source 0 to--5 V 2=Current programming source 0 to +10 V
Figure 4-3g. Series 664xA and 665xA Analog Programming Connections
If you cannot avoid capacitive coupling, it may help to place capacitors from the unused programming inputs to ground.
Especially with auto-parallel operation, connecting a capacitor (≥4,000 pF) from VP to P Common on the master supply
will ensure proper operation. Also with auto-parallel operation, do not allow more than about 500 pF capacitive loading
between IM and Common P.
Programming Considerations. When voltage programming the output, the frequency of the programming source is limited
by the slew rate of the power supply. To keep the power supply from slewing its output (going into nonlinear operation), the
maximum programming rate is 3750 V/s. The maximum downprogramming rate (when the power supply is sinking current)
is 750 V/s. These restrictions can be expressed as the maximum programming frequency that can be applied without causing
distortion at the output. The following formula can be used to determine this frequency:
FMAX = 50(voltage rating of supply)
p-p amplitude of desired output sine wave
At frequencies >6 kHz, voltage programming is subject to a 3 dB bandwidth limitation.
Connecting Series 667xA Power Supplies To The Load
Output Isolation
The output of the power supply is isolated from earth ground. Either output terminal may be grounded, or an external
voltage source may be connected between either output and ground. However, both output terminals must be kept within
± 240 Vdc of ground. An earth ground terminal is provided on the rear panel for convenience, such as grounding wire
shields.