Datasheet

MM5452, MM5453
SNLS367C –FEBRUARY 1995–REVISED MARCH 2013 www.ti.com
FUNCTIONAL DESCRIPTION
The MM5452 is specifically designed to operate 4½-digit 7-segment displays with minimal interface with the
display and the data source. Serial data transfer from the data source to the display driver is accomplished with 2
signals, serial data and clock. Since the MM5452 does not contain a character generator, the formatting of the
segment information must be done prior to inputting the data to the MM5452. Using a format of a leading “1”
followed by the 32 data bits allows data transfer without an additional load signal. The 32 data bits are latched
after the 36th clock is complete, thus providing non-multiplexed, direct drive to the display. Outputs change only if
the serial data bits differ from the previous time.
A block diagram is shown in Figure 1. For the MM5452 a DATA ENABLE is used instead of the 33rd output. If
the DATA ENABLE signal is not required, the 33rd output can be brought out. This is the MM5453 device.
Figure 7 shows the input data format. A start bit of logical “1” precedes the 32 bits of data. At the 36th clock a
LOAD signal is generated synchronously with the high state of the clock, which loads the 32 bits of the shift
registers into the latches. At the low state of the clock a RESET signal is generated which clears all the shift
registers for the next set of data. The shift registers are static master-slave configuration. There is no clear for
the master portion of the first shift register, thus allowing continuous operation.
If the clock is not continuous, there must be at least a complete set of 36 clocks otherwise the shift registers will
not load and clear.
Bit 1 is the first bit following the start bit and it will appear on device pin 18 of the MM5452N and MM5453N, and
on device pin 20 of the MM5452V and MM5453V.
Figure 6 shows the timing relationships between data, clock and DATA ENABLE.
Figure 6. Timing Diagram
Figure 7. Input Data Format
Figure 8 shows a typical application. Note how the input data maps to the output pins and the display. The
MM5452 and MM5453 do not have format restrictions, as all outputs are controllable. The application assumes a
specific display pinout. Different display/driver connection patterns will, of course, yield a different input data
format.
4 Submit Documentation Feedback Copyright © 1995–2013, Texas Instruments Incorporated
Product Folder Links: MM5452 MM5453