Capacitive Loads

NI DC Power Supplies and SMUs Help (NI-DCPower)

Edition Date: January 2018

Part Number: 370736U-01

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Generally, a power supply or SMU remains stable when driving a capacitive load. Occasionally, certain capacitive loads can cause ringing in the transient response of the device. The device may temporarily move into constant current mode or unregulated mode when the output voltage is reprogrammed while capacitive loads are present.

The slew rate is the maximum rate of change of the output voltage as a function of time. When driving a capacitor, the slew rate is limited to the output current limit divided by the total load capacitance, as expressed in the following equation:

(ΔV/Δt) = (I/C) 

where   ΔV is the change in the output voltage

Δt is the change in time

I is the current limit

C is the total capacitance across the load

Series resistance and lead inductance from cabling can affect the stability of the device. In some situations, you may need to increase the capacitive load or locally bypass the circuit or system being powered to stabilize the power supply or SMU.

Related Topics

Constant Current Mode

Constant Voltage Mode

Load Regulation

Transient Response

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