ICL8211 Datasheet, PDF (13/14 Pages) Intersil Corporation – Programmable Voltage Detectors

ICL8211, ICL8212
Since there is no internal compensation in the ICL8212 it is
necessary to use a large capacitor across the output to
prevent oscillation.
Zener voltages from 2V to 30V may be programmed and typ-
ical impedance values between 300µA and 25µA will range
from 4Ω to 7Ω. The knee is sharper and occurs at a signifi-
cantly lower current than other similar devices available.
V+
1
8
=
OR
2
7
I
1
8
3
6
2
7
4
5
3
6
4
5
I
I = 25µA (ICL8212)
I = 130µA (ICL8211)
FIGURE 32. CONSTANT CURRENT SOURCE APPLICATIONS
6
5
V+
4
I_S
V+
3
ICL
8212 ^500K _R2
2
V_TH
+
150K _{R1 – 5µF}
1
OUT
0
0.01
0.1
1.0
10
100
SUPPLY CURRENT (mA)
FIGURE 33. PROGRAMMABLE ZENER VOLTAGE REFERENCE
Precision Voltage Regulator (Figure 34)
The ICL8212 may be used as the controller for a highly sta-
ble series voltage regulator. The output voltage is simply pro-
grammed, using a resistor divider network R₁ and R₂. Two
capacitors C₁ and C₂ are required to ensure stability since
the ICL8212 is uncompensated internally.
V+
1
8
UNREG-
ULATED
2 ^ICL8212
7
DC SUPPLY
3
6
4
5
R₃
Q₁
V+
R₂
C₂
R₁
C₁
V_OUT =
R₂ + R₁
R₁
x 1.15V
FIGURE 34. PRECISION VOLTAGE REGULATOR
This regulator may be used with lower input voltages than
most other commercially available regulators and also con-
sumes less power for a given output control current than any
commercial regulator. Applications would therefore include
battery operated equipment especially those operating at
low voltages.
High Supply Voltage Dump Circuit (Figure 35)
In many circuit applications it is desirable to remove the
power supply in the case of high voltage overload. For
circuits consuming less than 5mA this may be achieved
using an ICL8211 driving the load directly. For higher load
currents it is necessary to use an external pnp transistor or
darlington pair driven by the output of the ICL8211.
Resistors R₁ and R₂ set up the disconnect voltage and R₃
provides optional voltage hysteresis if so desired.
V+
R₂
R₃
R₁
1
8
2 ^ICL8211 7
3
6
4
5
V+
CIRCUIT
BEING
PROTECTED
V-
V-
(a)
V+
R₂
R₃
R₁
V-
1
8
2 ^ICL8211 7
3
6
4
5
(b)
R₄
V+
CIRCUIT
BEING
PROTECTED
V-
FIGURE 35. HIGH VOLTAGE DUMP CIRCUITS
Frequency Limit Detector (Figure 36)
Simple frequency limit detectors providing a GO/NO-GO out-
put for use with varying amplitude input signals may be con-
veniently implemented with the ICL8211/8212. In the
application shown, the first ICL8212 is used as a zero cross-
ing detector. The output circuit consisting of R₃, R₄ and C₂
results in a slow output positive ramp. The negative range is
much faster than the positive range. R₅ and R₆ provide hys-
teresis so that under all circumstances the second ICL8212
is turned on for sufficient time to discharge C₃. The time con-
stant of R₇ C₃ Is much greater than R₄ C₂. Depending upon
the desired output polarities for low and high input frequen-
cies, either an ICL8211 or an ICL8212 may be used as the
output driver.
This circuit is sensitive to supply voltage variations and
should be used with a stabilized power supply. At very low
frequencies the output will switch at the input frequency.
Switch Bounce Filter (Figure 37)
Single pole single throw (SPST) switches are less costly and
more available than single pole double throw (SPDT) switches.
7-173