ICM7217AIPI Intersil, ICM7217AIPI Datasheet - Page 8

• Manufacturer Part Number: ICM7217AIPI
• Description: 4 DIGIT UP/DOWN COUNTER 0-9999
• Manufacturer: Intersil
• Type: 4-Digit UP/Down Counterr

Specifications of ICM7217AIPI

• Rohs Status: RoHS non-compliant
• Count: 9999
• Frequency: 2MHz
• Voltage - Supply: 4.5 V ~ 5.5 V
• Current - Supply: 100mA
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 28-DIP (0.600", 15.24mm)
• Other names: ICM7217AIPIIS

sponding to average segment currents of 3.1mA. Figure 1
shows the multiplex timing. The DISPLAY pin controls the
display output using three level logic. The pin is self-biased
to a voltage approximately
normal operation. When this pin is connected to V
segments are disabled and when connected to V
leading zero blanking feature is inhibited. For normal opera-
tion (display on with leading zero blanking) the pin should be
left open. The display may be controlled with a 3 position
The internal oscillator output has a duty cycle of
approximately 25:1, providing a short pulse occurring at the
oscillator frequency. This pulse clocks the four-state counter
which provides the four multiplex phases. The short pulse
width is used to delay the digit driver outputs, thereby provid-
ing inter-digit blanking which prevents ghosting. The digits
are scanned from MSD (D4) to LSD (D1). See Figure 1 for
the display digit multiplex timing.
CAPACITOR
SCAN
None
20pF
90pF
TABLE 1. ICM7217 MULTIPLEXED RATE CONTROL
1MΩ
10kΩ
R1
OSCILLATOR
FREQUENCY
NOMINAL
1.25kHz
2.5kHz
600Hz
FIGURE 10A.
1
R2
20kΩ
/
2
10kΩ
200Ω
(V
0.01µF
REPETITION
C
DD
625Hz
300Hz
150Hz
DIGIT
RATE
); this corresponds to
FIGURE 10. BRIGHTNESS CONTROL CIRCUITS
0.05µF
SCAN INPUT
ICM7217
(4 DIGITS)
7
2
6
CYCLE
SCAN
1.6ms
3.2ms
TIME
8ms
DD
SS
ICM7555
8
1
, the
, the
FIGURE 10C.
ICM7217
8s
4
3
8
0.05µF
SPDT switch; see Test Circuit.
Multiplex SCAN Oscillator
The on-board multiplex scan oscillator has a nominal free-
running frequency of 2.5kHz. This may be reduced by the
addition of a single capacitor between the SCAN pin and the
positive supply. Capacitor values and corresponding nomi-
nal oscillator frequencies, digit repetition rates, and loading
times are shown in Table 1.
During load counter and load register operations, the
multiplex oscillator is disconnected from the SCAN input and
is allowed to free-run. In all other conditions, the oscillator
may be directly overdriven to about 20kHz, however the
external oscillator signal should have the same duty cycle as
the internal signal, since the digits are blanked during the
time the external signal is at a positive level (see Figure 1).
To insure proper leading zero blanking, the interdigit blank-
ing time should not be less than about 2µs. Overdriving the
oscillator at less than 200Hz may cause display flickering.
The display brightness may be altered by varying the duty
cycle. Figure 10 shows several variable-duty-cycle oscilla-
tors suitable for brightness control at the ICM7217 SCAN
input. The inverters should be CMOS CD4000 series and
the diodes may be any inexpensive device such as lN914.
Counting Control, STORE, RESET
As shown in Figure 2, the counter is incremented by the
3kΩ
1MΩ
SCAN INPUT
ICM7217
V
500Ω
500Ω
DD
FIGURE 10B.
= 5V
0V
0.01µF
SCAN INPUT
ICM7217