The M54685L is an IC that can control the forward rotation, reverse rotation and speed of small DC brush motor. For the basic operation of this IC, output modes are selected, as shown in the logic truth table at right, by applying appropriate TTLlevel input to R, L and STB inputs. The PLAY mode is a mode where speed is controllable and is used to control the speed of motor by using two resistances, RT and RS, as shown in the application example. RT and RS are generally given by the following formulae: RT = KRa (K: current proportional constant, Ra: Motor armature resistance)