Datasheet MM74C925, MM74C926, MM74C927, MM74C928 Datasheet (Fairchild)

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MM74C925 • MM74C926 • MM74C927 • MM74C928
4-Digit Counters with Multiplexed

7-Segment Output Drivers

MM74C925 • MM74C926 • MM74C927 • MM74C928 4-Digit Counters with Multiplexed 7-Segment Output Drivers

October 1987
Revised January 1999

General Description

The MM74C925, MM74C 9 26, M M74 C92 7 and MM7 4C 9 28
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 Disp lay Select
input will select the number in the coun ter to be displ ayed;
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 MM74C9 25 except that it ha s a
display select and a carry-out used for cascading counters.
The carry-out sig nal goes HIGH at 6000 , goes back LOW
at 0000.

The MM74C927 is like the M M74C926 except the second
most significant digi t divides by 6 rather than 10. Thu s, 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 sig­nificant digit divides by 2 rather than 10 and the carry-out is
an overflow indicator which is HIGH at 2000, and it goes

Ordering Code:

back LOW only when the count er is reset. Thus, thi s is a

3½-digit counter.

Features

■ Wide supply voltage range: 3V to 6V

■ Guaranteed noise margin: 1V

■ High noise immunity: 0.45 V

■ High segment sourcing current: 40 mA

− 1.6V, VCC = 5V

@ V

CC

■ Internal multiplexing circuitry

CC

(typ.)

Design Considerations

Segment resistors are desirable to minimize po wer dissipa­tion and chip heating. The D S754 92 se rves as a good digit
driver when it is desired to drive bright displays. When
using this driver w it h a 5V su pp ly a t r oom tem pera tur e, the
display can be driven without segment resistors to full illu­mination. The user must use cautio n in thi s mo de however,
to prevent overheating of the d evice by using too high a
supply voltage or by operati ng at high ambient tempera­tures.

The input protection circ uitry consists of a series resist or,
and a diode to gro und. Thus input signals exceeding V

will not be clamped. This input signal should not be allowed
to exceed 15V .

CC

Order Number Package Number Package Description

MM74C925N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
MM74C926N N18A 18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
MM74C927N N18A 18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
MM74C928N N18A 18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide

© 1999 Fairchild Semiconductor Corporation DS005919.prf www.fairchildsemi.com

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

MM74C925 • MM74C926 • MM74C927 • MM74C928

Clock —Negative edge sensitive

Low, latch condition

Logic Diagrams

MM74C926, MM74C927, MM74C928

Segment Output — Current sourcing with 40 mA @V

Digit Output — Current sourcing with 1 mA @V

Carry-Out — 2 LTTL loads. See carry-out waveforms.

MM74C925

V

CC

LTTL loads

1.75V. Also, sink capability = 2 LTTL loads

Top View

− 1.6V (typ.) Also, sink capability = 2

OUT

OUT

=

=

www.fairchildsemi.com 2

Logic Diagrams (Continued)

MM74C925 • MM74C926 • MM74C927 • MM74C928

MM74C926

MM74C927

MM74C928

3 www.fairchildsemi.com

Absolute Maximum Ratings(Note 1)

Voltage at Any Output Pin GND − 0.3V to VCC + 0.3V
Voltage at Any Input Pin GND − 0.3V to +15V
Operatin g Temperature

Range (T

Storage Temperature
Range −65°C to +150°C

Power Dissipation (P

) −40°C to +85°C

A

)Refer to P

D

D(MAX)

vs TA Graph

Operating V
V

CC

Lead Temperature

(Soldering, 10 seconds) 260°C

Note 1: “Absolute Maxi mum Ratings” are those valu es beyond which the
safety of the device cannot be guaranteed. Ex ce pt for “O perating Tempera­ture Range” they are not mean t to imply that the devices sho uld be oper­ated at these limits. The Electrical Charac t eristics table provide s co nditions
for actual device operation.

Range 3V to 6V

CC

DC Electrical Characteristics

Min/Max limits apply at −40°C ≤ tj≤ + 85°C, unless otherwise noted

Symbol Parameter Conditions Min Typ Max Units

CMOS TO CMOS

V

IN(1)

V

IN(0)

V

OUT(1)

V

OUT(0)

I

IN(1)

I

IN(0)

I

CC

MM74C925 • MM74C926 • MM74C927 • MM74C928

CMOS/LPTTL INTERFA CE

V

IN(1)

V

IN(0)

V

OUT(1)

V

OUT(0)

OUTPUT DRIVE

V

OUT

R

ON

I

I

SOURCE

I

SINK

θ

jA

Note 2: θjA measured in free-air w it h device soldered into print ed circuit board.

Logical “1” Input Voltage VCC = 5V 3.5 V
Logical “0” Input Voltage VCC = 5V 1.5 V
Logical “1” Output Voltage VCC = 5V, IO = −10 µA
(Carry-Out and Digit Output 4.5 V
Only)
Logical “0” Output Voltage VCC = 5V, IO = 10 µA0.5V
Logical “1” Input Current VCC = 5V, VIN = 15V 0.005 1 µA
Logical “0” Input Current VCC = 5V, VIN = 0V −1 −0.005 µA
Supply Current VCC = 5V, Outputs Open Circuit, 20 1000 µA

VIN = 0V or 5V

Logical “1” Input Voltage VCC = 4.75V VCC − 2V
Logical “0” Input Voltage VCC = 4.75V 0.8 V
Logical “1” Output Voltage VCC = 4.75V,
(Carry-Out and Digit IO = −360 µA2.4 V
Output Only)
Logical “0” Output Voltage VCC = 4.75V, IO = 360 µA0.4V

Output Voltage (Segment I
Sourcing Output) I

= −65 mA, VCC = 5V, Tj = 25°CVCC − 2VCC − 1.3 V

OUT

= −40 mA, VCC = 5V Tj = 100°CVCC − 1.6 VCC − 1.2 V

OUT

Tj = 150°CVCC − 2VCC − 1.4 V
Output Resistance (Segment I
Sourcing Output) I

= −65 mA, VCC = 5V, Tj = 25°C2032Ω

OUT

= −40 mA, VCC = 5V Tj = 100°C3040Ω

OUT

Tj = 150°C3550Ω
Output Resistance (Segment 0.6 0.8 %/°C
Output) Temperature Coefficient
Output Source Current VCC = 4.75V, V

SOURCE

= 1.75V, Tj = 150°C −1 −2mA

OUT

(Digit Output)
Output Source Current VCC = 5V, V

= 0V, Tj = 25°C −1.75 −3.3 mA

OUT

(Carry-Out)
Output Sink Current VCC = 5V, V

= VCC, Tj = 25°C 1.75 3.6 mA

OUT

(All Outputs)
Thermal Resistance MM74C925: (Note 2) 75 100 °C/W

MM74C926, MM74C927, MM74C928 70 90 °C/W

6.5V

www.fairchildsemi.com 4

AC Electrical Characteristics (Note 3)

= 25°C, CL = 50 pF, unless otherwise noted

T

A

Symbol Parameter Conditions Min Typ Max Units

f

MAX

tr, t
t

WR

t

WLE

t

SET(CK, LE)

t

LR

t

SET(R, LE)

f

MUX

C

IN

Note 3: AC Parameters are guaranteed by DC correlated testing.
Note 4: Capacitance is guaranteed by periodic testing.

Maximum Clock Frequency VCC = 5V, Tj = 25°C24 MHz

Maximum Clock Rise or Fall Time VCC = 5V 15 µs

f

Reset Pulse Width VCC = 5V Tj = 25°C 250 100 ns

Latch Enable Pulse Width VCC = 5V Tj = 25°C 250 100 ns

Clock to Latch Enable Set-Up Time VCC = 5V Tj = 25°C 2500 1250 ns

Latch Enable to Reset Wait Time VCC = 5V Tj = 25°C0−100 ns

Reset to Latch Enable Set-Up Time VCC = 5V Tj = 25°C 320 160 ns

Multiplexing Output Frequency VCC = 5V 1000 Hz
Input Capacitance Any Input (Note 4) 5 pF

Squar e Wave Clock Tj = 100°C1.53 MHz

Tj = 100°C 320 125 ns

Tj = 100°C 320 125 ns

Tj = 100°C 3200 1600 ns

Tj = 100°C0−100 ns

Tj = 100°C 400 200 ns

Typical Performance Characteristics

MM74C925 • MM74C926 • MM74C927 • MM74C928

Typical Segment Current

vs Output Voltage

Note: VD = Voltage across digit driver

Maximum Power Dissipation

vs Ambient Temperature

Typical Average Segment

Current vs Segment

Resistor Value

5 www.fairchildsemi.com

Typical Performance Characteristics (Continued)

Segment Output Driver Input Protection

Common Cathode LED Display

MM74C925 • MM74C926 • MM74C927 • MM74C928

Segment Identification

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Switching Time Waveforms

Input Waveforms Multiplexing Output Waveforms

T = 1/f

MUX

Carry-Out Waveforms

MM74C925 • MM74C926 • MM74C927 • MM74C928

7 www.fairchildsemi.com

Physical Dimensions in ches (millimeters) unless otherwise noted

MM74C925 • MM74C926 • MM74C927 • MM74C928

16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide

Package Number N16E

www.fairchildsemi.com 8

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

MM74C925 • MM74C926 • MM74C927 • MM74C928 4-Digit Counters with Multiplexed 7-Segment Output Drivers

18-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide

LIFE SUPPORT POLICY

FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or system s a re devices or syste ms
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea­sonably expected to result in a significant injur y to the
user.

Package Number N18A

2. A critical comp onent in any com ponent of a l ife support
device or system whose failure to perform can be rea­sonably expected to cause the failure of the life suppor t
device or system, or to affect its safety or effectiveness.

www.fairchildsemi.com

Fairchild does not assume any responsibility for use of any circuitry described, no circui t patent licenses are implied and Fairchild reserves the right at any time without notice to change said circuitry and specifications.