6-7

TELCOM SEMICONDUCTOR, INC.

TC7211AM

BUS COMPATIBLE 4-DIGIT CMOS DECODER/DRIVER

FEATURES

4-Digit Non-Multiplexed 7-Segment LCD Outputs
With Backplane Driver

Input and Digit Select Data Latches

RC Oscillator On-Chip Generates Backplane
Drive Signal

Eliminates DC Bias Which Degrades LCD Life

Backplane Input/Output Pin Permits
Synchronization of Cascaded Slave Device to
a Master Backplane Signal

Binary and BCD Inputs Decoded to Code B
(0 to 9, --, E, H, L, P, Blank)

Pin Compatible and Functionally Equivalent to
ICM7211AM

GENERAL DESCRIPTION

The TC7211AM (LCD Decoder/driver) is a CMOS di-

rect drive, 4-digit, 7-segment display decoder and driver.

The TC7211AM drives conventional LCDs. An RC os-

cillator, divider chain, backplane driver, and 28-segment
outputs are provided on a single CMOS chip. The segment
drivers supply square waves of the same frequency as the
backplane, but in-phase for an OFF segment and out-of-
phase for an ON segment. The net DC voltage applied
between driver segment and backplane is near zero maxi-
mizing display lifetime.

The four bit binary input is decoded into the seven

segment alphanumeric code known as "Code B". The "Code
B" output format results in a 0 to 9,--, E, H, L, P or blank
display. True BCD or binary inputs will be correctly de-
coded to the seven segment display format.

ORDERING INFORMATION

Driver

Input

Output

Part No.

Type

Package Code

Config.

Data and

TC7211AMIPL

LCD

40-Pin

Code B

Digit Select

Plastic DIP

Latches

PIN CONFIGURATIONS

TC7211AM-4 11/14/96

TC7211AM (LCD)

OSCILLATOR

GND

DATA
INPUTS

CHIP SELECT 2 (CS2)

CHIP SELECT 1 (CS1)

DIGIT SELECT 2 (DS2

DIGIT SELECT 1 (DS1

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TELCOM SEMICONDUCTOR, INC.

BUS COMPATIBLE, 4-DIGIT

CMOS DECODER/DRIVER

TC7211AM

FUNCTIONAL BLOCK DIAGRAM

SEGMENT

OUTPUTS

SEGMENT

OUTPUTS

SEGMENT

OUTPUTS

SEGMENT

OUTPUTS

ENABLE

DETECTOR

OSCILLATOR

(16 kHz

FREE-

RUNNING)

�

128

BACK�
PLANE

DRIVER

ENABLE

BACKPLANE
(INPUT/OUTPUT)

V+

GND

DATA

INPUTS

DIGIT

SELECT

INPUTS

TC7211AM

PROGRAMMABLE

4-TO-7 DECODER

PROGRAMMABLE

4-TO-7 DECODER

PROGRAMMABLE

4-TO-7 DECODER

PROGRAMMABLE

4-TO-7 DECODER

7 WIDE
DRIVER

7 WIDE

LATCH ENABLE

7 WIDE

LATCH ENABLE

7 WIDE

LATCH ENABLE

7 WIDE

LATCH ENABLE

OSCILLATOR

INPUT

27
28
29

4-BIT

LATCH

B1
B2
B3

2-BIT

LATCH

2-TO-4

DECODER

DS1
DS2

31
32

33
34

CS1
CS2

ONE SHOT

ENABLE

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TELCOM SEMICONDUCTOR, INC.

Symbol

Parameter

Test Conditions

Min

Typ

Max

Unit

SUP

Operating Voltage Range

Operating Current

Display Blank

�

OSCI

Oscillator Input Current

Pin 36

�

RFS

Segment Rise/Fall Time

= 200 pF

0.5

�

sec

RFB

Backplane Rise/Fall Time

= 5000 pF

1.5

�

sec

OSC

Oscillator Frequency

Pin 36 Floating

kHz

Backplane Frequency

Pin 36 Floating

125

Input Characteristics

Logic "1" High Input Voltage

Logic "0" Low Input Voltage

ILK

Input Leakage Current

Pins 27�34

�

0.01

�

Input Capacitance

Pins 27�34

BPLK

BP Input Current

Measured at Pin 5 With

�

0.01

�

Leakage

Pin 36 at GND

BPI

BP Input Capacitance

All Devices

200

AC Characteristics

Symbol

Parameter

Test Conditions

CSA

Chip Select Active Pulse Width

(Note 1)

200

nsec

Data Setup Time

100

nsec

Data Hold Time

nsec

ICS

Inter-Chip Select Time

�

sec

NOTE: 1. Other chip select (CS) is either held at logic zero or both CS1 and CS2 driven together.

*Stresses above those listed under "Absolute Maximum Ratings" may
cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions above
those indicated in the operational sections of the specifications is not
implied. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.

NOTES: 1. This limit refers to that of the package and will not be realized

during normal operation.

2. Due to the SCR structure inherent in the CMOS process,

connecting any terminal to voltages greater than V

or less

than GND may cause destructive latch-up. For this reason, it
is recommended that inputs from external sources not oper-
ating on the same power supply not be applied to the device
before its supply is established, and, in multiple supply
systems, the supply to the TC7211AM be turned on first.

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage ........................................................ +6.5V
Input Voltage, Any Terminal

(Note 2) .................................... V

+0.3V, GND �0.3V

Power Dissipation T

�

C (Note 1) ................... 1.23W

Operating Temperature Range ................ �20

�

C to +85

�

Storage Temperature Range ................. �65

�

C to +150

�

Lead Temperature (Soldering, 10 sec) ................. +300

�

TYPICAL CHARACTERISTICS:

All parameters measured with V+ = 5V, T

= 25

�

BUS COMPATIBLE, 4-DIGIT
CMOS DECODER/DRIVER

TC7211AM

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TELCOM SEMICONDUCTOR, INC.

INPUT DEFINITIONS

In this table, V

and GND are considered to be normal operating input logic levels. For lowest power consumption, input

signals should swing over the full supply.

Input

Pin No.

Condition

Function

= Logic "1"

GND = Logic "0"

Ones (Least Significant)

= Logic "1"

GND = Logic "0"

Twos

= Logic "1"

GND = Logic "0"

Fours

= Logic "1"

GND = Logic "0"

Eights (Most Significant)

OSC

Floating or with

Oscillator input. Disables BP output devices, allowing segments to be

external capacitor GND

synchronized to an external signal input at the BP terminal (pin 5)

DS1

= Logical One

DS2, DS1 = 00 Selects D4
DS2, DS1 = 01 Selects D3

DS2

GND = Logical Zero

DS2, DS1 = 10 Selects D2
DS2, DS1 = 11 Selects D1

CS1

= Inactive

When both CS1 and CS2 are LOW, the data and digit select input
latches are open or enabled.

CS2

GND = Active

On the rising of CS1 or CS2, data is latched, decoded and stored in
the output drive latches.

BUS COMPATIBLE, 4-DIGIT
CMOS DECODER/DRIVER

TC7211AM

Digit Select Inputs

DIGIT ASSIGNMENT

OUTPUT DEFINITIONS

Output pins are defined by the alphabetical segment assignment and numerical digital assignment.

Output

Pin No.

Function

Output

Pin No.

Function

Segment Drive

Digit 1

(LSD)

Segment Drive

Digit 3

Segment Drive

Digit 2

Segment Drive

Digit 4

(MSD)

Data Input Bits

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TELCOM SEMICONDUCTOR, INC.

BUS COMPATIBLE, 4-DIGIT

CMOS DECODER/DRIVER

TC7211AM

If more than four devices are slaved together, the

backplane signal should be derived externally and all
TC7211AM devices slaved to it. The external drive signal
must drive a high capacitive load with 1

�

sec to 2

�

sec rise

and fall times. The backplane frequency is normally 125
Hz. At lower display ambient temperatures, the frequency
may be reduced to compensate for display response time.

The on-chip RC oscillator free-runs at approximately

16 kHz. A divide-by 128 circuit provides the 125 Hz backplane
frequency. The oscillator frequency may be reduced by
connecting an external capacitor between the oscillator
terminal and V

. (See typical operating characteristics

curves.)

The free-running oscillator may be overridden (if de-

sired) by an external clock. The backplane driver, however,
must not be disabled during the external clock's negative or
lOW portion, as this will result in a DC drive component
being applied to the LCD, limiting the LCD's life. To
prevent backplane driver disabling, the oscillator input
should be driven from the positive supply to no less than
one-fifth the supply voltage above ground. A backplane
disable signal will not be sensed if the driving signal remains
above ground by one-fifth the supply voltage. An alternate
method for externally driving the oscillator permits the
oscillator input to swing the full supply voltage range. The
oscillator input signal duty cycle is skewed so the LOW

BASIC OPERATION

The TC7211AM drives 4-digit, 7-segment LCDs. This

device contains 28 individual segment drivers, a backplane
driver, a self-contained oscillator, and a divider chain to
generate the backplane signal.

The 28 CMOS segment drivers and backplane driver

contain ratioed N- and P-channel transistors for identical ON
resistance. The equal resistances eliminate the DC output
driver component resulting from unequal rise and fall times.
This ensures maximum LCD life.

The backplane output driver can be disabled by ground-

ing the OSCILLATOR input (pin 36). The 28 output segment
drivers can therefore be synchronized directly to an input
signal at the backplane (BP) terminal (pin 5). Several slave
devices may be cascaded to the backplane output of a
master device. The backplane signal may also be derived
from an external source. These features permit interfacing to
single backplane LCDs with characters in multiples of four.

Each slave's backplane input represents a 200pF

capacitive load to the master backplane driver (comparable
to one additional segment). The number of slave devices
drivable by a master device is therefore set by the larger
display backplane capacitive load. The master backplane
output will drive the display backplane of 16 one-half-inch
characters with rise and fall times under 5

�

sec. This

represents a system with three slave devices and a fourth
master device driving the backplane.

TYPICAL CHARACTERISTICS

Operating Supply Current

vs Supply Voltage

TA= �20

�

TA= +70

�

TA= +25

�

V+ VOLTS

I OP

(

�

LCD DEVICES
DISPLAY BLANK
PIN 36 OPEN

180

150

120

Backplane Frequency

vs Supply Voltage

COSC = 0 pF

V+ VOLTS

BP (Hz)

COSC = 22 pF

COSC = 220 pF

(PIN 36 OPEN)

TA = +25

�

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TELCOM SEMICONDUCTOR, INC.

Binary Input

Character Displayed

(Code B)

Blank

portion duration is less than 1

�

sec. The backplane disable

sensing circuit will not respond to such a short signal.

Input Configuration and Output Codes

The TC7211AM accepts a 4-bit, true binary (positive

level = logic "1") input at pin 27 (LSB) through pin 30 (MSB).
The binary input is decoded to the 7-segment output known
as Code B. The output display format is 0 to 9, --, E, H, L,
P and blank display (see Table 1). Segment assignments
are shown in Figure 4. The TC7211AM will correctly decode
binary and BCD true codes to a 7-segment output.

The TC7211AM is designed to interface with a data bus

and display data under microprocessor control. Four data
inputs (pins 27�30) and two digit select input bits (pins 31
and 32) are written into input buffer latches. The rising edge
of either chip select causes data to be latched, decoded and
stored in the selected digit output data latch. The 2-bit digit
code selects the appropriate output digit latch. The 4-bit
display data word is decoded to the "Code B" 7-segment
output format.

For applications where bus compatibility is not required,

refer to the TC7211AM (LCD) 4-digit decoder driver data
sheet. This device is designed to accept multiplexed BCD/
binary input data for display under the control of four sepa-
rate digit select control signals.

Figure 3. TC7211AM Driving an 8-Digit LCD Display

in Master/Slave Configuration

Figure 4. Segment Assignment

Special Order Decoder Option

The TC7211AM is mask programmed to give the 16

combinations of 7-segment output codes. For large volume
orders (50K pieces minimum), custom decoder options are
available. Contact TelCom Semiconductor for details.

D8 D7 D6 D5 D4

D3 D2 D1

8-DIGIT

LCD

BACKPLANE

SLAVE

BCD/BINARY

DATA

BACKPLANE

MASTER

BACKPLANE

+5V

V+

GND

OSC

SEGMENTS

HIGH ORDER

B3�

B0 CS1

+5V

V+

GND

OSC

SEGMENTS

HIGH ORDER

B3�

TC7211AM

DS1

CS2

DS2

CS1

DS1

CS2

DS2

CHIP

SELECT

DIGIT

SELECT

Table 1. Binary Codes Versus Character Displayed

BUS COMPATIBLE, 4-DIGIT
CMOS DECODER/DRIVER

TC7211AM

Электронный компонент: TC7211AM

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