ICM7216A Intersil Corporation, ICM7216A Datasheet - Page 13

• Manufacturer Part Number: ICM7216A
• Description: 8-digit, Multi-function, Frequency Counters/timers
• Manufacturer: Intersil Corporation

Test Circuit
Typical Applications
The lCM7216 has been designed for use in a wide range of
Universal and Frequency counters. In many cases, prescalers
will be required to reduce the input frequencies to under 10MHz.
Because INPUT A and INPUT B are digital inputs, additional
circuitry is often required for input buffering, amplification,
hysteresis, and level shifting to obtain a good digital signal.
The lCM7216A or lCM7216B can be used as a minimum
component complete Universal Counter as shown in
Figure 18. This circuit can use input frequencies up to
10MHz at INPUT A and 2MHz at INPUT B. If the signal at
INPUT A has a very low duty cycle it may be necessary to
use a 74LS121 monostable multivibrator or similar circuit to
stretch the input pulse width to be able to guarantee that it is
at least 50ns in duration.
To measure frequencies up to 40MHz the circuit of Figure
19 can be used. To obtain the correct measured value, it is
necessary to divide the oscillator frequency by four as well
as the input frequency. In doing this the time between
U.C.
O.F.
FR
TI.
F
P
6
FUNCTION
OVERFLOW
INDICATOR
GENERATOR
GENERATOR
FUNCTION
FUNCTION
D2
D5
D8
D4
D1
D3
LED
RESET
10K
INPUT B
DP
e
g
a
d
b
c
f
8
a
b
c
d
e
f
g
DP
D8
FIGURE 17. TEST CIRCUIT (ICM7216A SHOWN, OTHERS SIMILAR)
10
11
12
13
14
1
2
3
4
5
6
7
8
9
INPUT A
ICM7216A
ICM7216A, ICM7216B, ICM7216D
D8
100pF
28
27
26
25
24
23
22
21
20
19
18
17
16
15
D7
V
DD
HOLD
D1
D2
D3
D4
D5
D6
D7
D8
9-22
D6
measurements is also lengthened to 800ms and the display
multiplex rate is decreased to 125Hz.
If the input frequency is prescaled by ten, then the oscillator
can remain at 10MHz or 1MHz, but the decimal point must
be moved one digit to the right. Figure 20 shows a frequency
counter with a
is no external decimal point control with the lCM7216A and
lCM7216B, the decimal point may be controlled externally
with additional drivers as shown in Figure 20. Alternatively, if
separate anodes are available for the decimal points, they
can be wired up to the adjacent digit anodes. Note that there
can be one zero to the left of the decimal point since the
internal leading zero blanking cannot be changed. In
Figure 21 additional logic has been added to count the input
directly in period mode for maximum accuracy. In Figures 20
and 21, INPUT A comes from Q
than Q
V
DD
10k
10k
10k
D5
D
22M
to obtain an input duty cycle of 40%.
V
DD
CRYSTAL
39pF
10MHz
D4
D1
D4
10
D2
D3
prescaler and an lCM7216A. Since there
RANGE
V
8
DD
39pF
DISPLAY
.01/1
.1/10
1/100
10/1K
D3
TYP
TYPICAL CRYSTAL SPECS:
F = 10MHz PARALLEL RESONANCE
C
R
BLANK
L
S
= 22pF
= <35
D4
DISPLAY
D2
TEST 1MHz
C
D8
of the prescaler rather
4
1N914s
D1
D2
OSC
EXT
INPUT
OSC
EXT
D1
TEST
8
D5