Fairchild Semiconductor MM74C911N Datasheet

October 1987 Revised January 1999

MM74C911 4-Digit Expandable Segment Display Controller

General Description

The MM74C911 display controller is an interface element with memory th at drives a 4-digit, 8-seg ment LED d isplay. The MM74C911 allows individual control of any segment in the 4-digit display. The number of segments per digit can be expanded without any exter nal c omponent s. For example, two MM74C911’s can be cascade d to drive a 16-se gment alpha-numeric display.

The display controllers receive data infor mation through 8

data lines a, b…DP, and digit information through 2 address inputs K1 and K2. The input data is written into the register selected by the address information when CHIP ENABLE, CE, a nd WRITE ENABLE, WE, are LOW and is latched when either CE

or WE return HIGH. Data hold time

is not required. A self-contained internal oscillator sequentially presents

the stored data to hi g h d r ive (100 m A typ.) 3-STATE output drivers which directly drive the LED display. The drivers are active when the control pin labeled SEGMENT OUTPUT ENABLE, SOE, is LOW and go into 3-STATE when SOE is HIGH. This feature allows for duty cycle brightness control, or for disabling the output drive for power conservation.

The digit outputs dire ctl y d r ive the ba se of the d ig it t ransistor when the control pi n labeled DIGIT INPUT OUTPUT

DIO

, is LOW. When DIO is HIGH, the digit lines turn into

inputs and the internal scanning multiplexer is disabled. When any digit line is forced H IGH by an external device,

usually another MM74 C911, the data information for that digit is presented to the output. In this manner, 16-segment alpha-numeric displ ays, 24- or 32-segment di splays, or an array of discrete LED's can be controlled by the simple cascading of expandable segment display controllers. All inputs except digit inpu ts are TTL compatible and do not clamp input voltages above V

Features

■ Direct segment drive (100 mA typ.) 3-STATE

■ 4 registers addressed like RAM

■ Internal oscillator and scanning circuit

■ Direct base drive to digit transistor

■ Segment expandability without external components

■ TTL compatible inputs

■ Power saver mode—5 µW (typ.)

Ordering Code:

Connection Diagram

Pin Assignments for DIP

Top View

Order Number Package Number Package Description

MM74C991N N28B 28-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS−010, 0.600” Wide

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MM74C911

Truth Tables

Input Control Output Control

R = Refresh (digit line s se quentially pulsed) X = Don’t Care

Functional Description

The MM74C911 display controller is manufactured on standard metal gate CMOS techno logy. A single 5V 74 series TTL supply can be used for power and should be bypassed at the V

pin to suppress current transients.

The digit outputs directly drive the base of a grounded emitter digit transistor without the need of a Darlington configuration. If an MM 74C911 i s drivi ng a digit transistor an d also supplying digit information to a cascaded MM74C911, base resistors are nee de d in th e di g it transistors to provide an adequate high level to the digit inputs of the cascaded MM74C911.

As seen in the Block Diagram, these display controllers contain four 8-bit registe rs; any on e may be randoml y wr it-

ten into. In normal op eratio n, the i nte rnal multiplexer scans the registers and refresh es th e di sp lay. In cascaded operation, 1 MM74C911 serves as a master refresh device and cascaded MM74C911’s are slaved to it throu gh digit lines operating as inputs.

The MM74C911 appea rs to a microprocessor a s memory and to the user as a self-scan display. Since every segment is under microprocessor control, great versatility is obtained.

Low power standby operation occurs w ith both SOE

and

DIO

inputs HIGH. This condition forces the MM74C911 to a quiescent state typically drawing less than 1 µA of supply current with a standby supply voltage as low as 3V.

Logic Diagram

Digit

Address WE Operation

K2 K1

0 0 0 0 Write Digit 1 0 0 0 1 Latch Digit 1 0 0 1 0 Write Digit 2 0 0 1 1 Latch Digit 2 0 1 0 0 Write Digit 3 0 1 0 1 Latch Digit 3 0 1 1 0 Write Digit 4 0 1 1 1 Latch Digit 4 1 X X X Disable Writing

DIO SOE Digit Lines Operation

D4 D3 D2 D1

0 0 RRRRRefresh Display 0 1 RRRRDisable Segment Outputs 1 0 0000Digits Are Now Inputs 1 0 0001Display Digit 1 1 0 0010Display Digit 2 1 0 0100Display Digit 3 1 0 1000Display Digit 4 1 1 0000Power Saver Mode

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MM74C911

Absolute Maximum Ratings(Note 1)

(Note 2)

Note 1: “Absolute Maximum Rat ings” are tho se values beyond which the safety of the device cannot be guarant eed. Exce pt for “Operating Range”, they are not meant to imply that the device should be operated at these limits. The table of “Electr ical Characteristic s” provides condition s for actual device operation.

Note 2: All voltage reference to ground.

DC Electrical Characteristics

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

Note 3: θJA measured in free-air with device soldered into printed circuit board.

Voltage at Any Pin

except Inputs −0.3V to V

+ 0.3V

Voltage at Any Input

except Digits −0.3V to +15V

Operating Temperature

Range, (T

) −40°C to +85°C Storage Temperature Range −65°C to +150°C Power Dissipation (P

) Refer to P

D(MAX)

vs TA Graph

Operating V

Range 3V to 6V

Absolute Maximum V

6.5V

Lead Temperature

(Soldering , 10 seconds) 260°C

Symbol Parameter Conditions Min Typ Max Units

IN(1)

Logical “1” Input Voltage VCC = 5V 3.0 V

IN(0)

Logical “0” Input Voltage 1.5 V

IN(1)

Logical “1” Input Current VCC = 5V, VIN = 15V 0.005 1.0 µA

IN(0)

Logical “0” Input Current VCC = 5V, VIN = 0V −1.0 −0.005 µA

Supply Current (Normal) VCC = 5V, Outputs Open 0.50 2.5 mA

Supply Current (Power Saver)

VCC = 5V, SOE, DIO = “1”,

1 600 µA

D1, D2, D3, D4 = “0”

OUT

3-STATE Output Current VO = 5V 0.03 10 µA

VO = 0V −10 −0.03

CMOS/LPTTL INTERFACE

IN(1)

Logical “1” Input Voltage VCC = 4.75V VCC − 2V

IN(0)

Logical “0” Input Voltage VCC = 4.75V 0.8 V

OUTPUT DRIVE

HIGH Level Segment Current VCC = 5V, VO = 3.4V

TJ = 25°C −60 −100 mA TJ = 100°C −40 −60 mA

HIGH Level Digit Current VCC = 5V, VO = 3V

TJ = 25°C −10 −20 mA TJ = 100°C −7 −10 mA VCC = 5V, VO = 1V TJ = 25°C −15 −40 mA TJ = 100°C −10 −15 mA

OUT(1)

Logical “1” Output Voltage, VCC = 5V, IO = −360 µA4.6 V Any Digit

OUT(0)

Logical “0” Output Voltage, VCC = 5V, IO = 360 µA0.4V Any Output

Thermal Resistance (Note 3) 100 °C/W

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