ICM7224 Intersil Corporation, ICM7224 Datasheet - Page 6

• Manufacturer Part Number: ICM7224
• Description: 41/2 Digit LCD Display Counter
• Manufacturer: Intersil Corporation

interfacing to CMOS logic in general, and are specifically
designed to allow cascading of the devices in four-digit
blocks.
Applications
Figure 8 shows an 8-digit precision frequency counter. The
circuit uses two ICM7224s cascaded to provide an 8-digit
display. Backplane output of the second device is disabled
and is driven by the first device. The
second device is used for overflow indication. The input sig-
nal is fed to the first device and the COUNT input of the sec-
ond is driven by the CARRY output of the first. Notice that
leading zero blanking is controlled on the second device and
the LZB OUT of the second one is tied to LZB IN of the first
one. An ICM7207A device is used as a timebase generator
and frequency counter controller. It generates count window,
store and reset signals which are directly compatible with
ICM7224 inputs (notice the need for an inverter at COUNT
INHIBIT input). The ICM7207A provides two count window
signals (1s and 0.1s gating) for displaying frequencies in Hz
or tens of Hz (x10Hz).
EACH SEGMENT TO
BACKPLANE WITH
200pF CAPACITOR
200pF
200pF
200pF
200pF
FIGURE 6. TEST CIRCUIT
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
+
5V
V
BP
DD
-
COUNT INHIBIT
ICM7224
OSCILLATOR
LZB OUT
1
/
COUNT
CARRY
STORE
RESET
2
LZB IN
1
DIGIT
/
2
V
SS
digit output of the
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
ICM7224
6
FIGURE 7. SEGMENT ASSIGNMENT AND DISPLAY FONT
e
f
d
g
a
c
b
DP
(BLANK)