ICM7242_07 Datasheet, PDF (5/10 Pages) Intersil Corporation – Long Range Fixed Timer

ICM7242
To use the 8-bit counter without the timebase, Terminal 7
(RC) should be connected to ground and the outputs taken
from Terminals 2 and 3.
The ICM7242 may be used for a very low frequency square
wave reference. For this application the timing components
are more convenient than those that would be required by a
555 timer. For very low frequencies, devices may be
cascaded (see Figure 3).
V_DD
1
8R
1
8
C
2
7
2
7
ICM7242
3
6
ICM7242
3
6
4
5
4
5
f = RC/2¹⁶
FIGURE 3. LOW FREQUENCY REFERENCE (OSCILLATOR)
For monostable operation the ÷2⁸ output is connected to the
RESET terminal. A positive edge on TRIGGER initiates the
cycle (NOTE: TRIGGER overrides RESET).
V_DD
OUTPUT
1
8
2
7
ICM7242
3
6
4
5
R
C
TRIGGER
S₁
RESET
100kΩ
TRIGGER
TERMINAL 6
TB OUTPUT
TERMINAL 8
OUTPUT
TERMINAL 3
FIGURE 4. MONOSTABLE OPERATION
The ICM7242 is superior in all respects to the 2242 except
for initial accuracy and oscillator stability. This is primarily
due to the fact that high value p-resistors have been used on
the ICM7242 to provide the comparator timing points.
TABLE 1. COMPARING THE ICM7242 WITH THE 2242
CHARACTERISTICS
ICM7242
2242
Operating Voltage
2V to 16V
4V to 15V
Operating Temperature Range -25°C to 85°C 0°C to 70°C
Supply Current, V_DD = 5V
Pullup Resistors
0.7mA (Max) 7mA (Max)
TB Output
No
Yes
÷2 Output
No
Yes
÷256 Output
No
Yes
Toggle Rate
3.0MHz
0.5MHz
Resistor to Inhibit Oscillator
No
Yes
Resistor in Series with Reset for
No
Yes
Monostable Operation
Capacitor TB Terminal for HF
Operation
No
Sometimes
By selection of R and C, a wide variety of sequence timing
can be realized. A typical flow chart for a machine tool
controller could be as shown in Figure 5.
TRIGGERING CAN BE
OBTAINED FROM A
PREVIOUS STAGE,
START
A LIMIT SWITCH,
O- PERATOR SWITCH, ETC.
ICM7242
WAIT
5s
ICM7242
ENABLE
10s
STOP
ENABLE
5s
ICM7242
COUNT
TO 185
ICM7240
WAIT
5s
ICM7242
START
STOP
WAIT ENABLE WAIT
5s
10s
5s
COUNT ENABLE
TO 185
5s
FIGURE 5. FLOW CHART FOR MACHINE TOOL CONTROLLER
By cascading devices, use of low cost CMOS AND/OR gates
and appropriate RC delays between stages, numerous
sequential control variations can be obtained. Typical
applications include injection molding machine controllers,
phonograph record production machines, automatic
sequencers (no metal contacts or moving parts), milling
machine controllers, process timers, automatic lubrication
systems, etc.
Sequence Timing
• Process Control
• Machine Automation
• Electro-Pneumatic Drivers
• Multi Operation (Serial or Parallel Controlling)
5
FN2866.4
February 9, 2007