7.3.2 VS Pin

The LM5050-1 VS pin is the main supply pin for all internal biasing and an auxiliary supply for the internal gate drive charge pump.

For typical LM5050-1 applications, where the input voltage is above 5 V, the VS pin can be connected directly to the OUT pin. In situations where the input voltage is close to, but not less than, the 5 V minimum, it may be helpful to connect the VS pin to the OUT pin through an RC Low-Pass filter to reduce the possibility of erratic behavior due to spurious voltage spikes that may appear on the OUT and IN pins. The series resistor value should be low enough to keep the VS voltage drop at a minimum. A typical series resistor value is 100 Ω. The capacitor value should be the lowest value that produces acceptable filtering of the voltage noise.

If Vs is powered while IN is floating or grounded, then about 0.5 mA will leak from the Vs pin into the IC and about 3mA will leak from the OUT pin into the IC. From this leakage, about 50 uA will flow out of the IN pin and the rest will flow to ground. This does not affect long term reliability of the IC, but may influence circuit design. See Reverse Input Voltage Protection With IQ Reduction for details on how to avoid this leakage current.

Alternately, it is possible to operate the LM5050-1 with V_IN value as low as 1 V if the VS pin is powered from a separate supply. This separate VS supply must be from 5 V and 75 V. See Figure 27.