CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES:
1. Due to the SCR structure inherent in the CMOS process, connecting any terminal to voltages greater than V
DD
or less than V
SS
may cause
destructive device latchup. For this reason, it is recommended that no inputs from external sources not operating on the same supply be applied
to the device before its supply is established and, that in multiple supply systems, the supply to the ICM7242 be turned on first.
2.
JA
is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
PARAMETER
Guaranteed Supply Voltage
Supply Current
V
DD
= 5V, T
A
= +25
°
C, R = 10k, C = 0.1µF, V
SS
= 0V, Unless Otherwise Specified
SYMBOL
V
DD
I
DD
Reset
Operating, R = 10k, C = 0.1µF
Operating, R = 1M, C = 0.1µF
TB Inhibited, RC Connected to V
SS
TEST CONDITIONS
MIN
2
-
-
-
-
-
f/t
V
OTB
Independent of RC Components
I
SOURCE
= 100µA
I
SINK
= 1.0mA
-
-
-
-
-
-
-
-
-
V
DD
= 2V
V
DD
= 5V
V
DD
= 15V
50% Duty Cycle Input with Peak to Peak
Voltages Equal to V
DD
and V
SS
Counter/Divider Mode
-
2
-
TYP
-
125
340
220
225
5
250
3.5
0.40
-
1.6
3.5
1.3
2.7
10
1
6
13
MAX
16
-
800
600
-
-
-
-
-
25
2.0
4.5
2.0
4.0
-
-
-
-
UNITS
V
µA
µA
µA
µA
%
ppm/°C
V
V
µA
V
V
V
V
µA
MHz
MHz
MHz
Timing Accuracy
RC Oscillator Frequency Temperature
Drift
Time Base Output Voltage
Time Base Output Leakage Current
Trigger Input Voltage
I
TBLK
V
TRIG
RC = Ground
V
DD
= 5V
V
DD
= 15V
Reset Input Voltage
V
RST
V
DD
= 5V
V
DD
= 15V
Trigger/Reset Input Current
Max Count Toggle Rate
I
TRIG
, I
RST
f
T
Output Saturation Voltage
Output Sourcing Current
MIN Timing Capacitor (Note 3)
Timing Resistor Range (Note 3)
NOTE:
3. For design only, not tested.
V
SAT
I
SOURCE
C
T
R
T
All Outputs Except TB Output V
DD
= 5V,
I
OUT
= 3.2mA
V
DD
= 5V Terminals 2 and 3, V
OUT
= 1V
-
-
10
0.22
300
-
-
0.4
-
-
22M
V
µA
pF
V
DD
= 2 - 16V
1k
FN2866 Rev 5.00
September 14, 2015
Page 3 of 11
ICM7242
Test Circuit
V
DD
1
÷2
1
(RC/2) OUTPUT
÷2
8
(RC/256) OUTPUT
2
3
4
8
7
6
5
RESET
TRIGGER
TIME BASE PERIOD = 1.0RC;
1s = 1M x 1µF
C
R
TIME BASE INPUT/OUTPUT
V
DD
NOTE:
4.
2
1
and
2
8
outputs are inverters and have active pullups.
Application Information
Operating Considerations
Shorting the RC terminal or output terminals to V
DD
may
exceed dissipation ratings and/or maximum DC current limits
(especially at high supply voltages).
There is a limitation of 50pF maximum loading on the TB I/O
terminal if the timebase is being used to drive the counter
section. If higher value loading is used, the counter sections
may miscount.
For greatest accuracy, use timing component values shown
in Figure 8. For highest frequency operation it will be
desirable to use very low values for the capacitor; accuracy
will decrease for oscillator frequencies in excess of 200kHz.
The timing capacitor should be connected between the RC
pin and the positive supply rail, V
DD
, as shown in Figure 1.
When system power is turned off, any charge remaining on
the capacitor will be discharged to ground through a large
internal diode between the RC node and V
SS
. Do NOT
reference the timing capacitor to ground, since there is no
high current path in this direction to safely discharge the
capacitor when power is turned off. The discharge current
from such a configuration could potentially damage the
device.
When driving the counter section from an external clock, the
optimum drive waveform is a square wave with an amplitude
equal to the supply voltage. If the clock is a very slow ramp
triangular, sine wave, etc., it will be necessary to “square up”
the waveform; this can be done by using two CMOS
inverters in series, operating from the same supply voltage
as the ICM7242.
The ICM7242 is a non-programmable timer whose principal
applications will be very low frequency oscillators and long
range timers; it makes a much better low frequency
oscillator/timer than a 555 or ICM7555, because of the on-
chip 8-bit counter. Also, devices can be cascaded to produce
extremely low frequency signals.
Because outputs will not be ANDed, output inverters are
used instead of open drain N-Channel transistors, and the
external resistors used for the 2242 will not be required for
the ICM7242. The ICM7242 will, however, plug into a socket
for the 2242 having these resistors.
The timing diagram for the ICM7242 is shown in Figure 1.
Assuming that the device is in the RESET mode, which
occurs on power up or after a positive signal on the RESET
terminal (if TRIGGER is low), a positive edge on the trigger
input signal will initiate normal operation. The discharge
transistor turns on, discharging the timing capacitor C, and
all the flip-flops in the counter chain change states. Thus, the
outputs on terminals 2 and 3 change from high to low states.
After 128 negative timebase edges, the
2
8
output returns to
the high state.
TRIGGER INPUT
(TERMINAL 6)
TIMEBASE INPUT
(TERMINAL 8)
÷2 OUTPUT
(TERMINAL 2)
÷128/256 OUTPUT
(TERMINAL 3) (ASTABLE
OR “FREE RUN” MODE)
÷128/256 OUTPUT
(TERMINAL 3)
(MONOSTABLE
OR “ONE SHOT” MODE)
128RC
128RC
128RC
FIGURE 1. TIMING DIAGRAMS OF OUTPUT WAVEFORMS
FOR THE ICM7242 (COMPARE WITH FIGURE 5)
V
DD
f
IN/2
OUTPUTS
f
IN/256
1
2
3
4
8
7
6
5
V
DD
f
IN
>
3
/
4
(V+)
<
1
/
4
(V+)
FIGURE 2. USING THE ICM7242 AS A RIPPLE COUNTER
(DIVIDER)
FN2866 Rev 5.00
September 14, 2015
Page 4 of 11
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
2
3
4
ICM7242
8
7
6
5
R
1
2
3
4
ICM7242
8
7
6
5
TABLE 1. COMPARING THE ICM7242 WITH THE 2242
CHARACTERISTICS
Operating Voltage
Operating Temperature Range
Supply Current, V
DD
= 5V
Pullup Resistors
TB Output
No
No
No
3.0MHz
No
No
No
Yes
Yes
Yes
0.5MHz
Yes
Yes
Sometimes
ICM7242
2V to 16V
-25°C to 85°C
0.7mA (Max)
2242
4V to 15V
0°C to 70°C
7mA (Max)
2 Output
C
256 Output
Toggle Rate
Resistor to Inhibit Oscillator
Resistor in Series with Reset for
Monostable Operation
Capacitor TB Terminal for HF
Operation
f = RC/2
16
FIGURE 3. LOW FREQUENCY REFERENCE (OSCILLATOR)
For monostable operation the
2
8
output is connected to the
RESET terminal. A positive edge on TRIGGER initiates the
cycle (NOTE: TRIGGER overrides RESET).
V
DD
R
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,
-
OPERATOR SWITCH, ETC.
STOP
ENABLE
5s
ICM7242
START
WAIT
5s
ENABLE
10s
WAIT
5s
COUNT
TO 185
ICM7242
WAIT
5s
ICM7242
ENABLE
10s
1
2
OUTPUT
3
4
ICM7242
8
7
6
5
100k
S
1
C
TRIGGER
COUNT
TO 185
ICM7240
WAIT
5s
ICM7242
STOP
RESET
TRIGGER
TERMINAL 6
ENABLE
5s
TB OUTPUT
OUTPUT
TERMINAL 8
TERMINAL 3
FIGURE 5. FLOW CHART FOR MACHINE TOOL CONTROLLER
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.
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)
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