Delta Electronics ND Series Features Descriptions Con, Input Under-Voltage Lockout, Remote sense

FEATURES DESCRIPTIONS (CON.)

Input Under-Voltage Lockout

The input under-voltage lockout prevents the converter from being damaged while operating when the input voltage is too low. The lockout occurs between 7.6V to 9.0V.

Over-Current and Short-Circuit Protection

The ND series modules have non-latching over-current and short-circuit protection circuitry. When over current condition occurs, the module goes into the non-latching hiccup mode. When the over-current condition is removed, the module will resume normal operation.

An over current condition is detected by measuring the voltage drop across the MOSFETs. The voltage drop across the MOSFET is also a function of the MOSFET’s Rds(on). Rds(on) is affected by temperature, therefore ambient temperature will affect the current limit inception point.

The detection of the Rds(on) of MOSFETs also acts as an over temperature protection since high temperature will cause the Rds(on) of the MOSFETs to increase, eventually triggering over-current protection.

Remote sense

The ND50 provide Vo remote sensing to achieve proper regulation at the load points and reduce effects of distribution losses on output line. In the event of an open remote sense line, the module shall maintain local sense regulation through an internal resistor. The module shall correct for a total of 0.5V of loss. The remote sense connects as shown in Figures 25.

Figure 25: circuit configuration for remote sense

DS_ND12S10A_07172008

Over Temperature Protection (OTP)

To provide additional over-temperature protection in a fault condition, the unit is equipped with a non-latching thermal shutdown circuit. The shutdown circuit engages when the temperature of monitored component exceeds approximately 125°C. The unit will cycle on and off while the fault condition exists. The unit will recover from shutdown when the cause of the over temperature condition is removed

Output Voltage Programming

The output voltage of the ND series is trimmable by connecting an external resistor between the trim pin and output ground as shown Figure 26 and the typical trim resistor values are shown in Figure 27.

Figure 26: Trimming Output Voltage

The ND50 module has a trim range of 0.9V to 3.63V. The trim resistor equation for the ND50A is:

Vout is the output voltage setpoint

Rs is the resistance between Trim and Ground Rs values should not be less than 3.32kΩ

Output Voltage	Rs (Ω)
0.9V	open
+1.2 V	38.3k
+1.5 V	18.7k
+1.8V	12.1k
+2.5 V	6.34k
+3.3V	3.92k
+3.63V	3.32k

Figure 27: Typical trim resistor values

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