ICL8211 Datasheet, PDF (8/14 Pages) Intersil Corporation – Programmable Voltage Detectors

ICL8211, ICL8212
Typical Performance Curves
(ICL8212 ONLY) (Continued)
0.6
0.5
OUTPUT SAT.
CURRENT
(V_O = 4.0V)
0.4
VOLTAGE SAT.
0.3
CURRENT
(I_O = 10mA)
0.2
0.1
V+ = +5V
V_TH = 1.2V
0
-55 -25 +5 +35 +65 +95 +125
TEMPERATURE (^oC)
FIGURE 18. OUTPUT SATURATION VOLTAGE AND CURRENT
AS A FUNCTION OF TEMPERATURE
40
T_A = +25^oC
V+ = +5V
30
V_TH =1.25V
20
V_TH = 1.158V
10
0
0.1
V_TH = 1.153V
1.0
10.0
OUTPUT VOLTAGE
30.0 100.0
FIGURE 19. OUTPUT CURRENT AS A FUNCTION OF OUTPUT
VOLTAGE
0
-5
V_T = 1.152V
-10
V_T = 1.153V
-15
-20
-25
V_T = 1.18V
-30
-35
T_A = +25^oC
V+ = +10V
-40
-10.00
-1.00
-0.10
-0.01
HYSTERESIS OUTPUT VOLTAGE
FIGURE 20. HYSTERESIS OUTPUT CURRENT AS A FUNCTION
OF HYSTERESIS OUTPUT VOLTAGE
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.
Components Q₁ through Q₁₀ and R₁, R₂ and R₃ set up an
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
thin film resistors (-5000 ppm per ^oC).
Components Q₂ through Q₉ and R₂ make up a constant
current source; Q₂ and Q₃ are identical and form a current
mirror. Q₈ has 7 times the emitter area of Q₉, and due to the
current mirror, the collector currents of Q₈ and Q₉ are forced
to be equal and it can be shown that the collector current in
Q₈ and Q₉ is
1
IC (Q₈ or Q₉) = _R2
kT
x
In7
q
or approximately 1µA at +25^oC
Where k = Boltzman’s Constant
q = Charge on an Electron
and T = Absolute Temperature in ^oK
Transistors Q₅, Q₆, and Q₇ assure that the V_CE of Q₃, Q₄,
and Q₉ remain constant with supply voltage variations. This
ensures a constant current supply free from variations.
The base current of Q₁ provides sufficient start up current for
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 transis-
tors is not sufficient in itself to guarantee reliable startup.
Q₄ is matched to Q₃ and Q₂; Q₁₀ is matched to Q₉. Thus the
IC and V_BE of Q₁₀ are identical to that of Q₉ or Q₈. To
generate the bandgap voltage, it is necessary to sum a
voltage equal to the base emitter voltage of Q₉ to a voltage
proportional to the difference of the base emitter voltages of
two transistors Q₈ and Q₉ operating at two current densities.
Thus 1.5 = V_BE (Q₉ or Q₁₀) +
R₃
R₂
x
kT
q
which provides:
R_{3 = 12 (approximately.)}
R₂
The total supply current consumed by the voltage reference
section is approximately 6µA at room temperature. A voltage
at the THRESHOLD input is compared to the reference 1.15V
by the comparator consisting of transistors Q₁₁ through Q₁₇.
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
500nA and the collector current of Q₁₉ to 100µA.
In the case of the ICL8211, Q₂₁ is proportioned to have 70
times the emitter area of Q₂₀ thereby limiting the output
current to approximately 7mA, whereas for the ICL8212
7-168