The NJW1871A is a current mode, boost/fly-back switching regulator controller with a wide voltage range from 4.5V to 40V. Its N-channel MOSFET driver circuit provides efficient driving, which makes it suitable for high-output current applications.
Connecting an external resistor to the FREQ pin allows the operating clock frequency to be set from 1 MHz to 2 MHz. An external clock signal applied to the SYNC pin can also be used to synchronise with other clock circuits. Due to the high switching frequency, the NJW1871 avoids AM band noise and allows the use of small inductors.
Phase compensation is a technique for stabilising the feedback loop of a regulating circuit. By connecting a capacitor and resistor between the ITH (current sense) and GND pins, the phase margin can be adjusted to ensure stability and prevent oscillations in the feedback loop. The soft start function gradually increases the regulator's output voltage when it's powered on. This helps prevent large inrush currents and voltage spikes that could damage components or destabilise the system. Gradually ramping up the voltage allows for a smoother start-up. The RUN pin is used in various scenarios, such as turning the chip on or off, determining a specific startup voltage, or entering a standby mode. Two divider resistors can be set to adjust the start-up voltage.
For enhanced safety, several circuits are incorporated to monitor for overvoltage, overcurrent, undervoltage lockout, and thermal overload. The Hiccup overcurrent protection feature allows automatic recovery after a specific delay, preventing heat generation during overload. The NJW1871A is suitable for boost / fly-back applications such as automotive and industrial instruments.
