ICL8211 Datasheet, PDF (9/14 Pages) Intersil Corporation – Programmable Voltage Detectors

ICL8211, ICL8212
almost all the collector current of Q₁₉ is available for base
drive to Q₂₁, resulting in a maximum available collector
current of the order of 30mA. It is advisable to externally limit
this current to 25mA or less.
Applications
The ICL8211 and ICL8212 are similar in many respects, espe-
cially with regard to the setup of the input trip conditions and
hysteresis circuitry. The following discussion describes both
devices, and where differences occur they are clearly noted.
General Information
Threshold Input Considerations
Although any voltage between -5V and V+ may be applied to
the THRESHOLD terminal, it is recommended that the
THRESHOLD voltage does not exceed about +6V since
above that voltage the threshold input current increases
sharply. Also, prolonged operation above this voltage will
lead to degradation of device characteristics.
The outputs change states with an input THRESHOLD
voltage of approximately 1.15V. Input and output waveforms
are shown in Figure 21 for a simple 1.15V level detector.
INPUT VOLTAGE
(RECOMMENDED
RANGE -5 TO +5V)
1
2
V_TH
3
4
V+
(V+ MUST BE
8
EQUAL OR
EXCEED 1.8V)
7
6
R_L1
5
V_O
V_HYST
such as TTL or CMOS using a single pullup resistor. There is
a guaranteed TTL fanout of 2 for the ICL8211 and 4 for the
ICL8212.
A principal application of the ICL8211 is voltage level
detection, and for that reason the OUTPUT current has been
limited to typically 7mA to permit direct drive of an LED
connected to the positive supply without a series current
limiting resistor.
On the other hand the ICL8212 is intended for applications
such as programmable zener references, and voltage
regulators where output currents well in excess of 7mA are
desirable. Therefore, the output of the ICL8212 is not current
limited, and if the output is used to drive an LED, a series
current limiting resistor must be used.
In most applications an input resistor divider network may be
used to generate the 1.15V required for V_TH. For high accu-
racy, currents as large as 50µA may be used, however for
those applications where current limiting may be desirable,
(such as when operating from a battery) currents as low as
6mA may be considered without a great loss of accuracy.
6mA represents a practical minimum, since it is about this
level where the device’s own input current becomes a signif-
icant percentage of that flowing in the divider network.
1
2
V_TH
3
4
V+
8
7
6
5
PULLUP RESISTOR
CMOS OR
TTL GATES
R_L2
V_O2
V_O1
FIGURE 22. OUTPUT LOGIC INTERFACE
INPUT
V+
1.15V
0
V+
0V
ICL8211 OUTPUT
V+
0V
ICL8212 OUTPUT
FIGURE 21. VOLTAGE LEVEL DETECTION
The HYSTERESIS output is a low current output and is
intended primarily for input threshold voltage hysteresis
applications. If this output is used for other applications it is
suggested that output currents be limited to 10µA or less.
The regular OUTPUT’s from either the ICL8211 or ICL8212
may be used to drive most of the common logic families
R₂
1
8
2
7
V_TH
3
6
4
5
R₁
V-
FIGURE 23. INPUT RESISTOR NETWORK CONSIDERATIONS
Case 1. High accuracy required, current in resistor network
unimportant Set I = 50µA for V_TH = 1.15V ∴ R₁ →
20kΩ
Case 2. Good accuracy required, current in resistor network
important Set I = 7.5µA for V_TH = 1.15V ∴ R₁ →
150kΩ
7-169