Datasheet

4
Schematic Diagram
Application Information
General
The ICM7555/6 devices are, in most instances, direct
replacements for the NE/SE 555/6 devices. However, it is
possible to effect economies in the external component
count using the ICM7555/6. Because the bipolar 555/6
devices produce 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 7555/6 devices
produce no such transients. See Figure 1.
The ICM7555/6 produces supply current spikes of only
2mA - 3mA instead of 300mA - 400mA and supply
decoupling is normally not necessary. Also, 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,
and 3 capacitors with an ICM7556.
POWER SUPPLY CONSIDERATIONS
Although the supply current consumed by the ICM7555/6
devices is very low, the total system supply current can be
high unless the timing components are high impedance.
Therefore, use high values for R and low values for C in
Figures 2 and 3.
RESET DISCHARGE
TRIGGER
THRESHOLD
GND
OUTPUT
CONTROL
VOLTAGE
R
NN
NPN
P
R
R
V
DD
NNNNN
PP
NN
PP P
R = 100kΩ ±20% (TYP)
TIME (ns)
400 8006002000
0
100
200
300
400
500
SUPPLY CURRENT (mA)
SE/NE555
T
A
= 25
o
C
ICM7555/56
FIGURE 1. SUPPLY CURRENT TRANSIENT COMPARED WITH
A STANDARD BIPOLAR 555 DURING AN OUTPUT
TRANSITION
GND
TRIGGER
OUTPUT
RESET
1
2
3
4
8
7
6
5
V
DD
DISCHARGE
THRESHOLD
CONTROL
VOLTAGE
V
DD
10K
ALTER-
OUTPUT
OPTIONAL
CAPACITOR
C
V
DD
NATE
R
FIGURE 2A. ASTABLE OPERATION
ICM7555, ICM7556