ICM7216A Datasheet, PDF (13/17 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

ICM7216A, ICM7216B, ICM7216D
Test Circuit
FUNCTION
GENERATOR
INPUT A
V_DD
V_DD
V_DD
DISPLAY DISPLAY
EXT
BLANK TEST _1MHz OSC _TEST
FUNCTION
GENERATOR
100pF
HOLD
10kΩ
10kΩ
39pF
39pF
TYP
1
28
INPUT B
2
27
FUNCTION
10K _DP
F
D1
e
P
D8
g
FR
D2
a
TI.
D5
U.C.
D4
d
O.F.
D3
b
c
f
3
26
4
25
5
24
6
23
7
22
ICM7216A
8
21
9
20
10
19
11
18
12
17
13
16
RESET
14
15
6
8
a
b
c
d
e
f
LED
g
OVERFLOW
DP
INDICATOR
D8
D8
D7
D4 D8 D2
D1 D5
22MΩ
10MHz
CRYSTAL
1N914s
EXT
OSC
INPUT
D1
8
D2
D3
D4
D5
V_DD
D6
D7
D8
10kΩ
TYPICAL CRYSTAL SPECS:
F = 10MHz PARALLEL RESONANCE
C_L = 22pF
R_S = <35Ω
RANGE
D1
.01/1
D2
.1/10
4
D3 1/100
D4
10/1K
8
D6
D5
D4
D3
D2
D1
FIGURE 17. TEST CIRCUIT (ICM7216A SHOWN, OTHERS SIMILAR)
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
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 ÷10 prescaler and an lCM7216A. Since there
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_C of the prescaler rather
than Q_D to obtain an input duty cycle of 40%.
9-22