ICM7242IPA Intersil, ICM7242IPA Datasheet - Page 4

• Manufacturer Part Number: ICM7242IPA
• Description: IC TIMER LONG RANGE FIXED 8-DIP
• Manufacturer: Intersil
• Type: Binary RC Timer/Counterr

Specifications of ICM7242IPA

• Count: 128/256
• Frequency: 15MHz
• Voltage - Supply: 2 V ~ 16 V
• Current - Supply: 340µA
• Operating Temperature: -25°C ~ 85°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: ICM7242IPAIS

Test Circuit
Application Information
Operating Considerations
Shorting the RC terminal or output terminals to V
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
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
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
NOTE:
4.
÷
2
1
and
÷
2
8
outputs are inverters and have active pullups.
÷2
÷2
8
(RC/256) OUTPUT
1
(RC/2) OUTPUT
4
DD
V
DD
, as shown in Figure 1.
1
2
3
4
SS
. Do NOT
DD
may
RESET
8
7
6
5
ICM7242
ICM7242
TIME BASE INPUT/OUTPUT
TRIGGER
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
the high state.
C
OUTPUTS
FIGURE 1. TIMING DIAGRAMS OF OUTPUT WAVEFORMS
FIGURE 2. USING THE ICM7242 AS A RIPPLE COUNTER
R
128RC
128RC
TIME BASE PERIOD = 1.0RC;
1s = 1MΩ x 1µF
V
f
f
DD
IN/2
IN/256
FOR THE ICM7242 (COMPARE WITH FIGURE 5)
(DIVIDER)
V
DD
1
2
3
4
128RC
8
7
6
5
V
f
IN
DD
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)
8
output returns to
February 9, 2007
<
>
1
3
FN2866.4
/
/
4
4
(V+)
(V+)