Transistor switch including independent control of turn-on and slew rate

Abstract

The disclosed transistor switching methodology enables independent control of transistor turn-on delay and slew rate, including charging, during a pre-charge period, a transistor control input to a threshold voltage Vwith a predetermined turn-on delay; and then charging, during a switch-on period, the transistor control input from Vto an operating point with a predetermined slew rate. This methodology is adaptable to load switching applications, for example, to control a high side/low side load switch such that, during the switch on period, the output voltage supplied to the load rises from zero volts to an operating load voltage with the predetermined slew rate. In one embodiment, I_delay and I_slew_rate currents are used to charge the transistor control input respectively during the pre-charge and switch-on periods. In another embodiment, the I-delay and I-slew rate currents are controlled by a replica switch with a control input coupled to the control input of a main switch, with the replica switch characterized by a threshold voltage substantially identical to the main switch threshold voltage V.