DESIGN CONSIDERATIONS
The ND 50A uses two phase and voltage mode controlled buck topology. The output can be trimmed in the range of 0.9Vdc to 3.63Vdc with 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 the 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.
The converter provides an open collector Power Good signal. 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.
The converter has an over temperature protection which can protect itself by shutting down for an over temperature event. There is a thermal hysteresis of typically 20°C
Safety Considerations
It is recommended that the user to provide a fuse with TBD in the input line for safety. The output voltage
DS_ND12S10A_07172008
FEATURES DESCRIPTIONS
ENABLE (On/Off)
The ENABLE (on/off) input allows external circuitry to put the ND converter into a low power dissipation (sleep) mode. Positive ENABLE is available as standard.
Positive ENABLE units of the ND 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 0.8V.
The ENABLE input can be driven in a variety of ways as shown in Figures 23 and 24. If the ENABLE signal comes from the primary side of the circuit, the ENABLE can be driven through either a bipolar signal transistor (Figure 23). If the enable signal comes from the secondary side, then an
Figure 23: Enable Input drive circuit for ND series
Figure 24: Enable input drive circuit example with isolation.
7