Negative 5 Volt Power Supply

A negative 5 V supply circuit is easily built using a 7660 Negative Voltage Converter IC. It is my favourite approach for generating a negative voltage from a positive voltage and requires minimum components.

The LM565 PLL IC requires both positive and negative voltage supplies. I already have a positive supply and need to generate a negative supply from that. The current output from the 7660 chip is 10 mA and adequate to drive the PLL chip. Therefore, in this circuit, I am using a MAX1044 / ICL7660 to generate a -5 V rail.

12 V and 5 V Power Supply

I am using a voltage regulator for the +12 V rail, and another for the +5 V rail. Each regulator can cope with a 2-watt load. Although the total power consumption is less than 360 mA, a 500 mA quick blow fuse ought to provide adequate protection against short circuits.

The voltage regulators have a transient protection and reverse load protection, which might provide some protection against surges when the engine starts. I have added a 1N4937 for additional protection against reverse spike blocking and back EMF that can occur near engines where there are reactive loads present. Further information about this and all the other components is available in the documentation section of this article.

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