Although designed originally for ac plasma Applications, the SN75501C can be used to drive VFDs. The SN75501C is a 32-bit high-voltage display driver. A logic diagram of the SN75501C is shown in Figure 8-63(b). When used as a VFD driver, the strobe input is grounded and the sustain input is operated as an active high strobe input. The 32-bit serial shift register, capable of 4 MHz operation, registers the data on the positive edge of the clock. A logical “1” stored in the register will cause the respective output to pulse high when the sustain input is pulsed high. The outputs of the SN75501C are totem-pole outputs and a serial data output is provided for use in cascading multiple drivers. The use of the SN75501C as a VFD driver should be limited to applications where the IDBT (sustain high) inputs are 74µS or greater.