Revised January 2004
MM74C925 • MM74C926
4-Digit Counters with Multiplexed
7-Segment Output Drivers
General Description
Features
The MM74C925 and MM74C926 CMOS counters consist
of a 4-digit counter, an internal output latch, NPN output
sourcing drivers for a 7-segment display, and an internal
multiplexing circuitry with four multiplexing outputs. The
multiplexing circuit has its own free-running oscillator, and
requires no external clock. The counters advance on negative edge of clock. A HIGH signal on the Reset input will
reset the counter to zero, and reset the carry-out LOW. A
LOW signal on the Latch Enable input will latch the number
in the counters into the internal output latches. A HIGH signal on Display Select input will select the number in the
counter to be displayed; a LOW level signal on the Display
Select will select the number in the output latch to be displayed.
s Wide supply voltage range:
The MM74C925 is a 4-decade counter and has Latch
Enable, Clock and Reset inputs.
The MM74C926 is like the MM74C925 except that it has a
display select and a carry-out used for cascading counters.
The carry-out signal goes HIGH at 6000, goes back LOW
at 0000.
3V to 6V
s Guaranteed noise margin: 1V
s High noise immunity: 0.45 VCC (typ.)
s High segment sourcing current: 40 mA
@ VCC − 1.6V, VCC = 5V
s Internal multiplexing circuitry
Design Considerations
Segment resistors are desirable to minimize power dissipation and chip heating. The DS75492 serves as a good digit
driver when it is desired to drive bright displays. When
using this driver with a 5V supply at room temperature, the
display can be driven without segment resistors to full illumination. The user must use caution in this mode however,
to prevent overheating of the device by using too high a
supply voltage or by operating at high ambient temperatures.
The input protection circuitry consists of a series resistor,
and a diode to ground. Thus input signals exceeding VCC
will not be clamped. This input signal should not be allowed
to exceed 15V.
Ordering Code:
Order Number
Package Number
Package Description
MM74C925N
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
MM74C926N
N18B
18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300" Wide
Connection Diagrams
Pin Assignments for DIP
Top View
MM74C925
© 2004 Fairchild Semiconductor Corporation
Top View
MM74C926
DS005919
www.fairchildsemi.com
MM74C925 • MM74C926 4-Digit Counters with Multiplexed 7-Segment Output Drivers
October 1987
