SCLS902 February 2024 SN74LV8T594
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
In this application, the SN74LV8T594 is used to control seven-segment displays. Utilizing the serial output and combining a few of the input signals, this implementation reduces the number of I/O pins required to control the displays from sixteen to four. Unlike other I/O expanders, the SN74LV8T594 does not need a communication interface for control. It can be easily operated with simple GPIO pins.
There is no practical limitation to how many SN74LV8T594 devices can be cascaded. To add more, the serial output will need to be connected to the following serial input and the clocks will need to be connected accordingly. With separate control for the shift registers and output registers, the desired digit can be displayed while the data for the next digit is loaded into the shift register. See the application note, Designing with Shift Registers, for solutions to common design challenges around cascading shift registers.
At power-up, the initial state of the shift registers and output registers are unknown. To give them a defined state, both registers need to be cleared. An RC network can be connected to the SRCLR and RCLR pins as shown to initialize the shift and output registers to all zeros.