─12 V from +5 V

There are many instances, especially in the field of microprocessors, where the majority of system power is required at the standard TT L level, but certain devices, memories for example, need a low power negative supply. No longer is it necessary to add an extra transformer for this negative supply line as there are now some very small board mounting DC to DC converters available, such as the AD1N12A10 from Astec, which can do the job very neatly. This device measures a mere 34 x 26 x 10 mm and is capable of providing a negative supply of 12 V at a current of up to 25 mA from a single positive 5 volt supply. The conversion efficiency of the -12 V from +5 V Uin = +5 V t 1 V Uout = —12 V/25 mA AD1N12A10 is rated at around 75% and the line and load regulation figures are quoted as 0.8% and 1% respectively. Although just one capacitor is required in the basic configuration the output ripple volt- age is only about 500 mV p—p. Astec supply a wide range of similar converters, all o...