7-168

ICL8211, ICL8212

Typical Performance Curves

(ICL8212 ONLY) (Continued)

FIGURE 18. OUTPUT SATURATION VOLTAGE AND CURRENT

AS A FUNCTION OF TEMPERATURE

FIGURE 19. OUTPUT CURRENT AS A FUNCTION OF OUTPUT

VOLTAGE

FIGURE 20. HYSTERESIS OUTPUT CURRENT AS A FUNCTION

OF HYSTERESIS OUTPUT VOLTAGE

-55

-25

+5

+35

+65

+95

+125

0.6

0.5

0.4

0.3

0.2

0.1

0

OUTPUT SAT.

CURRENT

VOLTAGE SAT.

CURRENT

V+ = +5V

40

30

20

10

0

0.1

1.0

10.0

30.0 100.0

OUTPUT VOLTAGE

V+ = +5V

0

-5

-10

-15

-20

-25

-30

-35

-40

-10.00

-1.00

-0.10

-0.01

HYSTERESIS OUTPUT VOLTAGE

V+ = +10V

Detailed Description

The ICL8211 and ICL8212 use standard linear bipolar

integrated circuit technology with high value thin film

resistors which define extremely low value currents.

accurate voltage reference of 1.15V. This reference voltage

is close to the value of the bandgap voltage for silicon and is

highly stable with respect to both temperature and supply

voltage. The deviation

from the

bandgap voltage

is

necessary due to the negative temperature coefficient of the

to be equal and it can be shown that the collector current in

or approximately 1

ensures a constant current supply free from variations.

the constant source; there being two stable states for this

type of circuit - either ON as defined above, or OFF if no start

up current is provided. Leakage current in the transistors is

not sufficient in itself to guarantee reliable startup.

generate the bandgap voltage, it is necessary to sum a

proportional to the difference of the base emitter voltages of

The total supply current consumed by the voltage reference

section is approximately 6

µA at room temperature. A voltage

at the THRESHOLD input is compared to the reference 1.15V

The outputs from the comparator are limited to two diode

drops less than V+ or approximately 1.1V. Thus the base cur-

rent into the hysteresis output transistor is limited to about

current to approximately 7mA, whereas for the ICL8212

1

x

kT

In7

R2

q

Where k = Boltzman’s Constant

q = Charge on an Electron

x

kT

q

which provides:

= 12 (approximately.)