decoupling in digital circuits

One important factor that is often sorely neglected in digital circuit design is decoupling the supply lines. The best known method of decoupling is by means of a small capacitor connected across the power supply pins of an IC. However, supply lines themselves also play a part in introducing interference, and this is the aspect of decoupling to which this article is dedicated. clecouplino Ill clioifal cIrcUlffy decoupling in digital circuits elektor november 1983 The power supply voltage in digital circuits must normally lie within fairly narrow limits in order to guarantee correct operation of the circuit. In TTL circuits this is particu- larly critical, and the supply must not devi- ate by more than + or — 5% from the nom- inal value of 5 V. There is no real difficulty in keeping the supply within these 5% limits, but we must also ensure that no voltage peaks greater than this 5% can exist in the circuit. Any wire, power lines included, has a specific self-inductance and a spe...