ICM7226A Просмотр технического описания (PDF) - Harris Semiconductor
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ICM7226A Datasheet PDF : 18 Pages
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ICM7226A, ICM7226B
Figure 23 shows the use of a CD4016 analog multiplexer to
multiplex the digital outputs back to the FUNCTION Input.
Since the CD4016 is a digitally controlled analog transmission
gate, no level shifting of the digit output is required. CD4051’s
or CD4052’s could also be used to select the proper inputs for
the multiplexed input on the ICM7226 from 2 or 3 bit digital
inputs. These analog multiplexers may also be used in sys-
tems in which the mode of operation is controlled by a micro-
processor rather than directly from front panel switches. TTL
multiplexers such as the 74LS153 or 74LS251 may also be
used, but some additional circuitry will be required to convert
the digit output to TTL compatible logic levels.
The circuit shown in Figure 24 can be used in any of the cir-
cuit applications shown to implement a single measurement
mode of operation. This circuit uses the STORE output to
put the ICM7226 into a hold mode. The HOLD input can also
be used to reduce the time between measurements. The cir-
cuit shown in Figure 25 puts a short pulse into the HOLD
input a short time after STORE goes low. A new measure-
ment will be initiated at the end of the pulse on the HOLD
input. This circuit reduces the time between measurements
to about 40ms from 200ms; use of the circuit shown in Fig-
ure 25 on the circuit shown in Figure 21 will reduce the time
between measurements from 800ms to about 160ms.
Using LCD Display
Figure 26 shows the ICM7226 being interfaced to LCD dis-
plays, by using its BCD outputs and 8 digit lines to drive two
ICM7211 display drivers.
STORE
OUTPUT
100kΩ
S1
VDD
100kΩ
S2
VDD
100kΩ
S3
VDD
SWITCH
S1
S2
S3
FUNCTION
Open-Single Meas Mode Enabled
Closed-Initiate New Measurement
Closed-Hold Input
HOLD
INPUT
STORE
OUTPUT
100kΩ
100pF
VDD
100kΩ
100pF
N.O.
HOLD SWITCH
HOLD
INPUT
FIGURE 24. SINGLE MEASUREMENT CIRCUIT FOR USE WITH FIGURE 25. CIRCUIT FOR REDUCING TIME BETWEEN MEA-
ICM7226
SUREMENTS
+5V
1
35
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28 SEGMENT LINES
5
ICM7211
28 SEGMENT LINES
5
ICM7211
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+5V
1
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
ICM7226A
27 28 29 30
D8 • • D1
FIGURE 26. 10MHz UNIVERSAL COUNTER SYSTEM WITH LCD DISPLAY
13-81
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