ICM7555CFE View Datasheet(PDF) - Philips Electronics
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ICM7555CFE Datasheet PDF : 9 Pages
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Philips Semiconductors Linear Products
General purpose CMOS timer
Product specification
ICM7555
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
100.0
10.0
(RA + 2RB)
VDD = 5V
TA = +25°C
1.0
0.1
0.01
0.001
0.0001
0.0
0.1
100.0
1kΩ
10kΩ
100kΩ
1MΩ
10MΩ
1.0
10
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Free-Running Frequency as a Function of RA, RB, and C
10.0
VDD = 5V
TA = +25°C
1.0
RA
0.1
0.01
1kΩ
10kΩ
100kΩ
0.001
1MΩ
0.0001
10MΩ
0.0
100ns
500
TA = +25°C
400
1µs
10µs
100µs
1ms
10ms
100ms
1s
10s
TIME DELAY
Monostable Time Delay vs RA and C
bipolar 555 device produces large crowbar currents in the output
driver, it is necessary to decouple the power supply lines with a
good capacitor close to the device. The 7555 device produces no
such transients. See Figure 1.
300
NE/SE555
200
100
ICM7555
0
0
200
400
600
800
TIME (ns)
Figure 1. Supply Current Transient
Compared With a Standard Bipolar 555
During an Output Transition
APPLICATION NOTES
General
The ICM7555 device is, in most instances, a direct replacement for
the NE/SE555 device. However, it is possible to effect economies in
the external component count using the ICM7555. Because the
The ICM7555 produces supply current spikes of only 2-3mA instead
of 300-400mA and supply decoupling is normally not necessary.
Secondly, in most instances, the CONTROL VOLTAGE decoupling
capacitors are not required since the input impedance of the CMOS
comparators on chip are very high. Thus, for many applications, 2
capacitors can be saved using an ICM7555.
Power Supply Considerations
Although the supply current consumed by the ICM7555 device is
very low, the total system supply can be high unless the timing
components are high impedance. Therefore, high values for R and
low values for C in Figures 2 and 3 are recommended.
Output Drive Capability
The output driver consists of a CMOS inverter capable of driving
most logic families including CMOS and TTL. As such, if driving
CMOS, the output swing at all supply voltages will equal the supply
voltage. At a supply voltage of 4.5V or more, the ICM7555 will drive
at least 2 standard TTL loads.
August 31, 1994
344
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