Turning Ideas Into Reality
ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104
CNT7 IC
Dual Decade Counter to Seven Segment Controller
General Description
The CNT7 IC is two decade counters with seven segment outputs for non multiplexed displays.
The counter can be used as an up counter or a down counter. More than one CNT7 chip may be
connected together to achieve larger displays. The CNT7 has internal pull resistors on inputs to
minimize additional parts. The chip also provides clear function, output polarity control and a
de-bounce circuit for mechanical switches. A .1 uF bypass capacitor is suggested across the
VDD and VSS pins. The part uses the standard 28 pin .3 inch width SOIC and DIP packages.
Features
•
Counter drives two seven segment
•
•
•
•
•
•
•
•
•
•
•
•
non multiplexed displays.
Up or down counter.
Mechanical or electronic inputs.
Few external parts required.
Low power consumption 5 mA
typical.
Supply voltage 3.3 to 5.25 volts.
On chip input pull up resistors.
Output polarity select.
TTL and CMOS compatible.
Part is in full production.
SOIC and DIP 28 Pin Package.
ROHS Compliant
Low EMI
Applications
•
Data Displays
•
Large display control
•
Numeric Displays
•
Controls
Part Number CNT7
Copyright © 2014 ABCircuits. Revised September 2014 Page 1 of 7
Turning Ideas Into Reality
ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104
POL
Polarity input. If this pin is open or high, the “on” segments will have a high level on the SEG
outputs of the chip. If this pin is low or grounded “on” segments will output as a low on the SEG
pins. This pin is read once at power up and has a built in pull up resistor.
UP
This input signal determines count direction, up or down. If this input is open or high, the counter
will count up. If this input is grounded or low, the counter will count down. This input is read once
at power up and has a built in pull up resistor.
CLR-
This input clears the counters when low. If the counter is in the up mode, the counter clears to
00. If the counter is in the down mode, the counter clears to 99. CLR is a software derived
function, and as such requires 1 mS of minimum input pulse width. This input has a built in pull up
resistor.
SW-
SW- and DEB form an optional switch de-bounce circuit. This input would be tied to a switch to
ground. An internal pull up resistor is provided.
DEB
This is the inverted output of the switch de-bounce circuit, which may be tied directly to the CLK
input if your design uses a mechanical switch. De-bounce time is about 37 mS, limiting input
speed to about 13 clocks per second. The output is push pull.
CLK
This is the input to the two hardware decade counters. On the positive edge of this input, the
counter increments the counters in UP mode; or decrements the counters in down mode. This
input does not have a pull up resistor. Maximum clock frequency is 12 MHz.
CB
This is the counters carry/borrow output. This signal ties to the clock of the next IC in the chain.
The output is push pull.
SEGRA, SEGRB, SEGRC, SEGRD, SEGRE, SEGRF, SEGRG
SEGLA, SEGLB, SEGLC, SEGLD, SEGLE, SEGLF, SEGLG
SEGR is the right hand of the two displays.
SEGL is the left hand of the two displays
If the POL pin is open or hi, this SEG outputs will be high when a segment is on.
If the POL pin is low or grounded, the SEG outputs will be low when a segment is on.
These are the seven segment outputs to each individual display An external driver or current
limiting resistor is required for each segment. If you are using only a resistor, it must be sized to
limit source current to 5 mA maximum per pin or sink current to 9 mA per pin.
See also the segment table, and the ASCII to seven segment translation table.
VSS
Connect to system ground.
Part Number CNT7
Copyright © 2014 ABCircuits. Revised September 2014 Page 3 of 7
Turning Ideas Into Reality
ABCircuits www.abcircuits.com POB 123 New Hill NC 27562 (919) 290-7104
Using Drivers For Brighter Displays
VCC
VCC
28
19
9
5
26
4
10
3
1
25
CLEAR
2
27
24
14
CLR-
POL
UP
VSS
VDD
NC
NC
NC
NC
NC
CB
CLK
DEB
SW-
SEGRG
SEGRF
SEGRE
SEGRD
SEGRC
SEGRB
SEGRA
18
11
17
12
16
13
15
1
2
3
4
5
6
7
8
CNT7
SEGLG
SEGLF
SEGLE
SEGLD
SEGLC
SEGLB
SEGLA
23
6
22
7
21
8
20
1
2
3
4
5
6
7
8
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
LEFT COMMON
ANODE
VCC
DISPLAY
A
COM
G
F
F
B
E
G
D
C
E
C
B
D
A
RIGHT COMMON
ANODE DISPLAY
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
VCC
18
17
16
15
14
13
12
11
G
F
E
D
C
B
A
A
COM
F
G
E
D
C
B
10
9
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
18
17
16
15
14
13
12
11
ULN2804
ULN2804
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
COUNT
COM
GND
VCC
Counter Expansion Example
DISPLAY
DISPLAY
DISPLAY
DISPLAY
DISPLAY
DISPLAY
IN
IN
IN
IN
IN
10
CB
SEGL
10
CB
SEGL
10
CB
SEGL
3
CLK
SEGR
3
CLK
SEGR
CLK
3
CLK
SEGR
DISPLAY EXPANSION EXAMPLE
Absolute Maximum Ratings
Symbol
T
stg
T
a
V
dd
V
io
I
mio
ESD
LU
Description
Storage Temperature
Operating Temperature
V
dd
- V
ss
Voltage
Input Voltage
Maximum current into any pin
Electrostatic Discharge Voltage
Latch up current
Min
-55
-40
-0.5
V
ss
- 0.5
-25
2000
Typical
25
Max
+100
+85
+6.0
V
dd
+0.5
+50
Units
ºC
ºC
V
V
mA
V
mA
Notes
Human Body Model
ESD
200
Part Number CNT7
Copyright © 2014 ABCircuits. Revised September 2014 Page 5 of 7
IN
CNT7
CNT7
9
10
GND
COM
CNT7
模拟电子
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