7-169

ICL8211, ICL8212

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.

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 10

µA or less.

The regular OUTPUT’s from either the ICL8211 or ICL8212

may be used to drive most of the common logic families

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

racy, currents as large as 50

µA 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.

FIGURE 22. OUTPUT LOGIC INTERFACE

FIGURE 23. INPUT RESISTOR NETWORK CONSIDERATIONS

Case 1. High accuracy required, current in resistor network

unimportant Set I = 50

µA for V

20k

Ω

Case 2. Good accuracy required, current in resistor network

important Set I = 7.5

µA for V

150k

Ω

1

2

3

4

8

7

6

5

INPUT VOLTAGE

(RECOMMENDED

RANGE -5 TO +5V)

V+

(V+ MUST BE

EQUAL OR

EXCEED 1.8V)

0

V+

1.15V

0V

V+

0V

ICL8211 OUTPUT

ICL8212 OUTPUT

1

2

3

4

8

7

6

5

V+

PULLUP RESISTOR

CMOS OR

TTL GATES

1

2

3

4

8

7

6

5

V+

INPUT

V-