The SN75581 (Figure 8-21) is a high-voltage (150 V). 7-channel, source output monolithic BIDFET integrated circuit designed to drive a dot matrix or segmented display. Its output characteristics make this driver compatible to several display types including vacuum fluorescent and de plasma displays.
All device inputs are diode-clamped pnp inputs and, when left open, assume a high logic level. The nominal input threshold is 1.5 V. Outputs are open source DMOS transistors for excellent high voltage characteristics and reliability.
The device consists of a 7-bit shift register, seven Latches, and seven output AND gates. Serial data is entered into the shift register on the low-to-high transition of the Clock input. When the Latch Enable input is high, data is transferred from the shift registers to the latch outputs. When Latch Enable makes a high-to-low transition, the shift register is cleared. Taking the Output Enable input high enables all outputs simultaneously. The Serial Output is not affected by the Output Enable input. See Figures 8-22 and 8-23.
A typical SN75581 gas discharge display driver application is shown in Figure 8-23. Serial data is clocked into the SN75581 under microprocessor control. When the latch enable input is high, the data is transferred from input shift registers to the latches. The latches store the data until output enable goes high, which enables all outputs (pins 9 through 16). The outputs are connected to a seven segment display (a through g). Individual segments (a through g) will fire if a data bit turns on the corresponding DMOS output transistor connected to that segment. Serial output is not utilized.