Delta Electronics NC30 manual Design Considerations, Features Descriptions, Enable On/Off

DESIGN CONSIDERATIONS

The NC30 is designed using two-phase synchronous buck topology. Block diagram of the converter is shown in Figure 25. The output can be trimmed in the range of 0.9Vdc to 5.0Vdc by a resistor from trim pin to ground. A remote sense function is provided and it is able to compensate for a drop from the output of converter to point of load.

The converter can be turned ON/OFF by remote control. Positive on/off (ENABLE pin) logic implies that the converter DC output is enabled when this signal is driven high (greater than 2.4V) or floating and disabled when the signal is driven low (below 0.8V). Negative on/off logic is optional and could also be ordered.

The converter provides an open collector signal called Power Good. The power good signal is pulled low when output is not within ±10% of Vout or Enable is OFF.

The converter can protect itself by entering hiccup mode against over current and short circuit condition. Also, the converter will shut down when an over voltage protection is detected.

FEATURES DESCRIPTIONS

ENABLE (On/Off)

The ENABLE (on/off) input allows external circuitry to put the NC converter into a low power dissipation (sleep) mode. Positive (active-high) ENABLE is available as standard.

Positive ENABLE (active-high) units of the NC series are turned on if the ENABLE pin is high or floating. Pulling the pin low will turn off the unit. With the active high function, the output is guaranteed to turn on if the ENABLE pin is driven above 2.4V. The output will turn off if the ENABLE pin voltage is pulled below .8V.

The ENABLE input can be driven in a variety of ways as shown in Figures 26, 27 and 28. If the ENABLE signal comes from the primary side of the circuit, the ENABLE can be driven through either a bipolar signal transistor (Figure

26)or a logic gate (Figure 27). If the enable signal comes from the secondary side, then an opto-coupler or other isolation devices must be used to bring the signal across the voltage isolation (please see Figure 28).

NC30/NC40

The converter has an over temperature protection which can protect itself by shutting down for an over

Vin

Vout

temperature event. There is a thermal hysteresis of typically 30℃

Figure 25: Block Diagram

Enable Trim

Ground Ground

Figure 26: Enable Input drive circuit for NC series

5V	NC30/NC40
	Vin	Vout
	Enable	Trim

Ground Ground

Figure 27: Enable input drive circuit using logic gate.

NC30/NC40

Safety Considerations

Vin Enable

Vout

Trim

It is recommended that the user to provide two 12A very fast-acting type fuses (Little fuse R451 012) in parallel in the input line for safety.

DS_NC12S30A_05222008

Ground Ground

Figure 28: Enable input drive circuit example with isolation.

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