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Fairchild
Fairchild

MM74C926 Datasheet

4-Digit Counters with Multiplexed


MM74C926 Datasheet Preview


October 1987
Revised January 1999
MM74C925 • MM74C926 • MM74C927 • MM74C928
4-Digit Counters with Multiplexed
7-Segment Output Drivers
General Description
The MM74C925, MM74C926, MM74C927 and MM74C928
CMOS counters consist of a 4-digit counter, an internal out-
put latch, NPN output sourcing drivers for a 7-segment dis-
play, 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 sig-
nal 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.
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.
The MM74C927 is like the MM74C926 except the second
most significant digit divides by 6 rather than 10. Thus, if
the clock input frequency is 10 Hz, the display would read
tenths of seconds and minutes (i.e., 9:59.9).
The MM74C928 is like the MM74C926 except the most sig-
nificant digit divides by 2 rather than 10 and the carry-out is
an overflow indicator which is HIGH at 2000, and it goes
back LOW only when the counter is reset. Thus, this is a
3½-digit counter.
Features
s Wide supply voltage range: 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 dissipa-
tion 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 illu-
mination. 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 tempera-
tures.
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
MM74C925N
MM74C926N
MM74C927N
MM74C928N
Package Number
Package Description
N16E
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
N18A
18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
N18A
18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
N18A
18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
© 1999 Fairchild Semiconductor Corporation DS005919.prf
www.fairchildsemi.com
Page 1

Connection Diagrams
Pin Assignments for DIP
Top View
MM74C925
Functional Description
Reset
— Asynchronous, active high
Display Select — High, displays output of counter
Low, displays output of latch
Latch Enable — High, flow through condition
Low, latch condition
Clock
—Negative edge sensitive
Logic Diagrams
Top View
MM74C926, MM74C927, MM74C928
Segment Output — Current sourcing with 40 mA @VOUT =
VCC 1.6V (typ.) Also, sink capability = 2
LTTL loads
Digit Output — Current sourcing with 1 mA @VOUT =
1.75V. Also, sink capability = 2 LTTL loads
Carry-Out — 2 LTTL loads. See carry-out waveforms.
MM74C925
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Page 2

Logic Diagrams (Continued)
MM74C926
MM74C927
MM74C928
3 www.fairchildsemi.com
Page 3

Absolute Maximum Ratings(Note 1)
Voltage at Any Output Pin
Voltage at Any Input Pin
Operating Temperature
Range (TA)
Storage Temperature
Range
Power Dissipation (PD)
GND 0.3V to VCC + 0.3V
GND 0.3V to +15V
40°C to +85°C
65°C to +150°C
Refer to PD(MAX) vs TA Graph
Operating VCC Range
VCC
Lead Temperature
(Soldering, 10 seconds)
3V to 6V
6.5V
260°C
Note 1: “Absolute Maximum Ratings” are those values beyond which the
safety of the device cannot be guaranteed. Except for “Operating Tempera-
ture Range” they are not meant to imply that the devices should be oper-
ated at these limits. The Electrical Characteristics table provides conditions
for actual device operation.
DC Electrical Characteristics
Min/Max limits apply at 40°C tj≤ + 85°C, unless otherwise noted
Symbol
Parameter
Conditions
Min
CMOS TO CMOS
VIN(1)
VIN(0)
VOUT(1)
Logical “1” Input Voltage
Logical “0” Input Voltage
Logical “1” Output Voltage
(Carry-Out and Digit Output
VCC = 5V
VCC = 5V
VCC = 5V, IO = −10 µA
Only)
VOUT(0)
IIN(1)
IIN(0)
ICC
Logical “0” Output Voltage
Logical “1” Input Current
Logical “0” Input Current
Supply Current
CMOS/LPTTL INTERFACE
VCC = 5V, IO = 10 µA
VCC = 5V, VIN = 15V
VCC = 5V, VIN = 0V
VCC = 5V, Outputs Open Circuit,
VIN = 0V or 5V
VIN(1)
VIN(0)
VOUT(1)
Logical “1” Input Voltage
Logical “0” Input Voltage
Logical “1” Output Voltage
(Carry-Out and Digit
Output Only)
VCC = 4.75V
VCC = 4.75V
VCC = 4.75V,
IO = −360 µA
VOUT(0)
Logical “0” Output Voltage
OUTPUT DRIVE
VCC = 4.75V, IO = 360 µA
VOUT
RON
Output Voltage (Segment
Sourcing Output)
Output Resistance (Segment
Sourcing Output)
Output Resistance (Segment
IOUT = −65 mA, VCC = 5V, Tj = 25°C
IOUT = −40 mA, VCC = 5V Tj = 100°C
Tj = 150°C
IOUT = −65 mA, VCC = 5V, Tj = 25°C
IOUT = −40 mA, VCC = 5V Tj = 100°C
Tj = 150°C
Output) Temperature Coefficient
ISOURCE Output Source Current
(Digit Output)
VCC = 4.75V, VOUT = 1.75V, Tj = 150°C
ISOURCE
Output Source Current
(Carry-Out)
VCC = 5V, VOUT = 0V, Tj = 25°C
ISINK
Output Sink Current
(All Outputs)
VCC = 5V, VOUT = VCC, Tj = 25°C
θjA Thermal Resistance
MM74C925: (Note 2)
MM74C926, MM74C927, MM74C928
Note 2: θjA measured in free-air with device soldered into printed circuit board.
3.5
4.5
1
VCC 2
2.4
VCC 2
VCC 1.6
VCC 2
1
1.75
1.75
Typ
0.005
0.005
20
VCC 1.3
VCC 1.2
VCC 1.4
20
30
35
0.6
2
3.3
3.6
75
70
Max
1.5
0.5
1
1000
0.8
0.4
32
40
50
0.8
100
90
Units
V
V
V
V
µA
µA
µA
V
V
V
V
V
V
V
%/°C
mA
mA
mA
°C/W
°C/W
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4
Page 4
Part Number MM74C926
Manufactur Fairchild
Description 4-Digit Counters with Multiplexed
Total Page 9 Pages
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MM74C922 , MM74C922 , MM74C922N , MM74C922WM , MM74C923 , MM74C923 , MM74C923N , MM74C923WM , MM74C925 , MM74C925 , MM74C925 , MM74C925N , MM74C926 , MM74C926 , MM74C926 , MM74C926N , MM74C927 , MM74C927 , MM74C927N , MM74C928 , MM74C928 , MM74C928N ,

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