ICM7556 Datasheet, PDF (4/11 Pages) Intersil Corporation – Precision Timing Pulse Generation Sequential Timing Time Delay Generation Pulse Width Modulation Missing Pulse Detector

Schematic Diagram
P
P
ICM7555, ICM7556
P
R
V_DD
P
THRESHOLD
N
CONTROL
VOLTAGE
N
R
TRIGGER
P
P
NPN
OUTPUT
R = 100kΩ ±20% (TYP)
R
N
N
N
N
N
RESET
N
N
DISCHARGE
GND
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.
500
T_A = 25^oC
400
300
SE/NE555
200
100
0
ICM7555/56
0
200
400
600
800
TIME (ns)
FIGURE 1. SUPPLY CURRENT TRANSIENT COMPARED WITH
A STANDARD BIPOLAR 555 DURING AN OUTPUT
TRANSITION
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.
OUTPUT
GND
1
TRIGGER
2
3
V_DD
4
RESET
R
V_DD
V_DD
8
10K
DISCHARGE
7
ALTER-
NATE
THRESHOLD
6
OUTPUT
5
CONTROL
VOLTAGE
C
OPTIONAL
CAPACITOR
FIGURE 2A. ASTABLE OPERATION
4