Replacing a regulator

To replace a monolithic regulator with a discrete model, you need to know its polarity, pinout and output voltage. In the case of an adjustable regulator, its output voltage is fixed by the circuit in which it is integrated via a resistor that must be short-circuited and removed.

It is not recommended to attempt to dynamically adjust the output voltage of these discrete regulators using potentiometers or voltage dividers on the ground pin to achieve the specified performance.

If a controller to be replaced is mounted on a heatsink, the same heatsink must be used with the replacement discrete controller. It is not necessary to use a larger heatsink. The existing heatsink will suffice. Since the tab of these discrete regulators is connected to the voltage input, an electrical insulator must be used between the tab and the heatsink.

The input and output shunt capacitors of the existing circuit should also be adapted and require no modification for normal operation. If the output capacitor closest to the regulator is of the ceramic or film type, a better transient response can be achieved by removing it from the circuit, since ceramic and film capacitors degrade the phase margin of the device. In cases where the output capacitor is removed from the circuit, the internal 10µF tantalum polymer capacitor will be sufficient as the output capacitor, and the device will operate with a higher phase margin and a less transient response.

The best transient response can be achieved by using a Panasonic EEU - FR1H101B (100µF 50V 65mΩ ESR) electrolytic capacitor as output capacitor. This capacitor can be used to replace the existing output capacitor or it can be added in parallel. Please note that the correct polarity must be observed when installing these electrolytic capacitors.