ICL8211 Datasheet, PDF (12/14 Pages) Intersil Corporation – Programmable Voltage Detectors

ICL8211, ICL8212
have dropped to zero. Upon power up to the normal
operating voltage this record must have been retained and
easily interrogated. This could be important in the case of a
transient power failure due to a faulty component or
intermittent power supply, open circuit, etc., where direct
observation of the failure is difficult.
A simple circuit to record an out of range voltage excursion
may be constructed using an ICL8211, an ICL8212 plus a
few resistors. This circuit will operate to 30V without exceed-
ing the maximum ratings of the ICs. The two voltage limits
defining the in range supply voltage may be set to any value
between 2.0V and 30V.
The ICL8212 is used to detect a voltage, V₂, which is the
upper voltage limit to the operating voltage range. The
ICL8211 detects the lower voltage limit of the operating
voltage range, V₁. Hysteresis is used with the ICL8211 so
that the output can be stable in either state over the
operating voltage range V₁ to V₂ by making V₃ - the upper
trip point of the ICL8211 much higher in voltage than V₂.
The output of the ICL8212 is used to force the output of the
ICL8211 into the ON state above V₂. Thus there is no value
of the supply voltage that will result in the output of the
ICL8211 changing from the ON state to the OFF state. This
may be achieved only by shorting out R3 for values of supply
voltage between V₁ and V₂.
Constant Current Sources (Figure 32)
The ICL8212 may be used as a constant current source of
value of approximately 25µA by connecting the THRESH-
OLD terminal to GROUND. Similarly the ICL8211 will pro-
vide a 130µA constant current source. The equivalent
parallel resistance is in the tens of megohms over the supply
voltage range of 2V to 30V. These constant current sources
may be used to provide basing for various circuitry including
differential amplifiers and comparators. See Typical Operat-
ing Characteristics for complete information.
Programmable Zener Voltage Reference (Figure 33)
The ICL8212 may be used to simulate a zener diode by
connecting the OUTPUT terminal to the V_Z output and using
a resistor network connected to the THRESHOLD terminal
to program the zener voltage
V_ZENER =
(R₁ + R₂)
R₁
x 1.l5V.
V+
R₃
S₁
R₄
1
8
RESET
1
8
2 ^ICL8212 7
2 ^ICL8211 7
3
6
R₆
3
6
4
5
R₂
4
5
R₅
OUTPUT
R₁
FIGURE 30. NON-VOLATILE POWER SUPPLY MALFUNCTION RECORDER
OUTPUT ICL8211
ICL8212 DISCONNECTED
OUTPUT ICL8212
OUTPUT ICL8211
AS PER FIGURE 7
OFF
V_NOM
OFF
V_NOM
OFF
ON
ON
ON
V₁
V₂
V₃
SUPPLY VOLTAGE
V₂
SUPPLY VOLTAGE
V₁
V₂
SUPPLY VOLTAGE
FIGURE 31. OUTPUT STATES OF THE ICL8211 AND ICL8212 AS A FUNCTION OF THE SUPPLY VOLTAGE
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