Operating Configurations, Stability | Agilent Technologies E4356A

Note The signal ground binding post on the rear panel is a convenient place to ground the sense shield.

OVP Considerations

The OVP circuit senses the voltage near the output terminals and not at the sense terminals. Depending on the voltage drop between the output terminals and the load, the voltage sensed by the OVP circuit can be significantly higher than actually being regulated at the load. You must program the OVP trip high enough to compensate for the expected higher voltage at the output terminals.

Stability

Using remote sensing under unusual combinations of load-lead lengths and large load capacitances may cause your application to form a low-pass filter that becomes part of the voltage feedback loop. The extra phase shift created by this filter can degrade the unit’s stability and result in poor transient response. In severe cases, this may cause output oscillations. To minimize this possibility, keep the load leads as short as possible and tie wrap them together.

In most cases, following the above guidelines will prevent problems associated with load lead inductance. However, if a large bypass capacitor is required at the load and load-lead length cannot be reduced, then a sense-lead bypass network may be needed to ensure stability (see Figure 4-4). The voltage rating of the 33 μF capacitors should be about 50% greater than the anticipated load-lead drop. Addition of the 20-Ωresistors will cause a slight voltage rise at the remote sensing points. For utmost voltage programming accuracy, the unit should be recalibrated with the DVM at the remote sensing points (see “Appendix B - Calibration”).

Note If you need help in solving a stability problem with the power supply, contact an Agilent Service Engineer through your local Agilent Sales and Support Office.

Load Leads				Remote Sense Points
Cl, C2 = 33 μF		C3 = Load bypass capacitor		R1, R2 = 20 Ω, 1%

Figure 4-4. Sense Lead Bypass Network