ICM7224 Datasheet, PDF (6/7 Pages) Intersil Corporation – 41/2 Digit LCD Display Counter

ICM7224
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 ¹/₂ digit output of 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).
+ ^5V -
a
fb
g
ec
d
DP
200pF
200pF
200pF
1 V_DD
40
2
ICM7224
39
3
38
4
37
5 BP
OSCILLATOR 36
6
V_SS 35
7
STORE 34
8
RESET 33
9
COUNT 32
10
COUNT INHIBIT 31
11
LZB OUT 30
12
LZB IN 29
13
CARRY 28
14
1_{/2 DIGIT 27}
15
26
16
25
17
24
18
23
19
22
20
21
200pF
EACH SEGMENT TO
BACKPLANE WITH
200pF CAPACITOR
FIGURE 6. TEST CIRCUIT
(BLANK)
FIGURE 7. SEGMENT ASSIGNMENT AND DISPLAY FONT
6