Agilent Technologies N3280A Current Priority Operation, Output Characteristic Current Priority

1 - General Information

If the output voltage exceeds either the positive or negative overvoltage set point, the output will shut down and be disabled, automatically opening the output and sense relays. This leaves the output in a high-impedance state.

The full ±512.5 milliampere output current is available only in voltage priority mode. In this mode, the output voltage should be programmed to the desired positive or negative value. A positive current limit value should also be programmed. Note that the negative current limit tracks the positive current limit set point. The output will regulate at the desired voltage level, provided that the current limit has been set higher that the actual output current requirement of the external load. Note that if the current limit is set to a value between zero and 75 ∝A, the actual current limit will be ±75 ∝A. Thus, it is not possible to program current limit values less than 75 ∝A in voltage priority mode. (This limitation does not apply in current priority mode.)

Current Priority Operation

Each Agilent N3280A output is a four-quadrant bipolar dc source that can be operated in either voltage or current priority mode. In current priority mode the output is controlled by a bi-polar constant current feedback loop, which maintains the output current (source or sink) at its programmed setting. The output current will remain at its programmed setting as long as the load voltage remains within the positive and negative voltage limits. The voltage limits are not programmable and vary somewhat with the output current. When the output current is zero, the voltage limits are typically ±10.75 V.

Figure 1-2 shows the current priority operating characteristics of the dc source. The area in quadrants 1 and 3 shows the characteristics of the unit when it is being operated as a source (sourcing power). The area in quadrants 2 and 4 shows the characteristics of the unit when it is being operated as a load (sinking power).

		Output		Key
+ 12V		Voltage		Sinking power
		+		Sourcing power
	+V limit	+ 10.75V
				Programmable
		+VL status set		+ 9.5V
			I setting
-		2 1		+ Output
		3 4		Current
- 9.5V
- 0.5125mA			-VL status set
		- 10.75V	-V limit	- 12V
		-
			+ 0.5125mA

Figure 1-2. Output Characteristic (Current Priority)

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