ICM7226A, ICM7226B
Figure 23 shows the use of a CD4016 analog multiplexer to to put the ICM7226 into a hold mode. The HOLD input can
multiplex the digital outputs back to the FUNCTION Input. also be used to reduce the time between measurements.
Since the CD4016 is a digitally controlled analog transmission The circuit shown in Figure 25 puts a short pulse into the
gate, no level shifting of the digit output is required. CD4051s HOLD input a short time after STORE goes low. A new mea-
or CD4052s could also be used to select the proper inputs for surement will be initiated at the end of the pulse on the
the multiplexed input on the ICM7226 from 2-bit or 3-bit digital HOLD input. This circuit reduces the time between measure-
inputs. These analog multiplexers may also be used in sys- ments to about 40ms from 200ms; use of the circuit shown in
tems in which the mode of operation is controlled by a micro- Figure 25 on the circuit shown in Figure 21 will reduce the
processor rather than directly from front panel switches. TTL time between measurements from 800ms to about 160ms.
multiplexers such as the 74LS153 or 74LS251 may also be
used, but some additional circuitry will be required to convert
Figure 26 shows the ICM7226 being interfaced to LCD dis-
the digit output to TTL compatible logic levels.
Using LCD Display
plays, by using its BCD outputs and 8 digit lines to drive two
The circuit shown in Figure 24 can be used in any of the
ICM7211 display drivers.
circuit applications shown to implement a single measure-
ment mode of operation. This circuit uses the STORE output
STORE
OUTPUT
HOLD
INPUT
100kΩ
S1
100kΩ
S3
V
DD
V
DD
V
DD
100kΩ
100kΩ
S2
100kΩ
100pF
STORE
OUTPUT
V
DD
HOLD
INPUT
100pF
SWITCH
S1
FUNCTION
N.O.
Open-Single Meas Mode Enabled
Closed-Initiate New Measurement
Closed-Hold Input
HOLD SWITCH
S2
S3
FIGURE 24. SINGLE MEASUREMENT CIRCUIT FOR USE WITH
ICM7226
FIGURE 25. CIRCUIT FOR REDUCING TIME BETWEEN
MEASUREMENTS
a
a
a
a
a
a
a
a
f
f
f
f
f
f
f
f
b
b
b
b
b
b
b
b
g
g
g
g
g
g
g
g
e
e
e
e
e
e
e
e
c
c
c
c
c
c
c
c
d
d
d
d
d
d
d
d
+5V
+5V
28 SEGMENT LINES
28 SEGMENT LINES
1
1
5
5
ICM7211
ICM7211
35
31 32 33 34
30 29 28 27
27 28 29 30
31 32 33 34
36 35
22 23 24 26
D8 D5
7
6
17 18
27 28 29 30
D8 D1
•
•
•
•
ICM7226A
FIGURE 26. 10MHz UNIVERSAL COUNTER SYSTEM WITH LCD DISPLAY
9-32
INTERSIL [ Intersil ]
