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Número de pieza CA3290
Descripción BiMOS Dual Voltage Comparators
Fabricantes Intersil 
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Data Sheet
CA3290, CA3290A
September 1998 File Number 1049.3
BiMOS Dual Voltage Comparators
with MOSFET Input, Bipolar Output
The CA3290A and CA3290 types consist of a dual voltage
comparator on a single monolithic chip. The common mode
input voltage range includes ground even when operated
from a single supply. The low supply current drain makes
these comparators suitable for battery operation; their
extremely low input currents allow their use in applications
that employ sensors with extremely high source
impedances. Package options are shown in the table below.
Pinout
CA3290/A (PDIP)
TOP VIEW
OUTPUT (A1) 1 A1
INV. INPUT (A1) 2
NON-INV. INPUT (A1) 3
V- 4
8 V+
7 OUTPUT (A2)
A2 6 INV. INPUT (A2)
5 NON-INV. INPUT (A2)
Features
• MOSFET Input Stage
- Very High Input Impedance (ZIN) . . . . . . . . 1.7T(Typ)
- Very Low Input Current at V+ = 5V . . . . . . . 3.5pA (Typ)
- Wide Common Mode Input Voltage Range (VICR) Can Be
Swung 1.5V (Typ) Below Negative Supply Voltage Rail
- Virtually Eliminates Errors Due to Flow of Input Currents
• Output Voltage Compatible with TTL, DTL, ECL, MOS,
and CMOS Logic Systems in Most Applications
Applications
• High Source Impedance Voltage Comparators
• Long Time Delay Circuits
• Square Wave Generators
• A/D Converters
• Window Comparators
Ordering Information
PART
NUMBER
CA3290AE
CA3290E
TEMP
RANGE (oC)
-55 to 125
-55 to 125
PACKAGE
8 Ld PDIP
8 Ld PDIP
PKG. NO.
E8.3
E8.3
Schematic Diagram
(ONLY ONE IS SHOWN)
COMPARATOR NO. 1
BIASING CIRCUIT
FOR CURRENT
SOURCES
V+
TO
COMP.
NO. 2
I1
50µA
I2
Q9
100µA
I3
Q10
50µA
I4
Q11
100µA
Q12
VO
D1
D2
Q1
+VI
Q2 Q3
D3
D4 Q8
Q4
-VI Q7
Q5 Q6
Q13 Q14
Q15
Q17
R1
100k
R2
1k
Q18
R3
5k
C1
5pF
Q16
V-
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Copyright © Intersil Corporation 1999

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CA3290 pdf
CA3290, CA3290A
Their gate source potentials (VGS) are supplied by a common
bus from the biasing circuit shown in the right hand portion of
the Schematic Diagram. The currents supplied by Q10 and
Q12 are twice those supplied by Q9 and Q11. The transistor
geometries are appropriately scaled to provide the requisite
currents with common VGS applied to Q9 through Q12.
V+
D1 D2
I1
50µA
I2
100µA
Q2 Q3
VI+ QP1
Q5 Q6
I3
50µA
D3 D4
VI-
QP4
I4
100µA
VO
Q8
Q7
V-
FIGURE 4. BASIC CIRCUIT DIAGRAM FOR ONE OF THE TWO
COMPARATORS
Operating Considerations
Input Circuit
The use of MOS transistors in the input stage of the CA3290
series circuits provides the user with the following features
for comparator applications:
1. Ultra high input impedance (1.7T);
2. The availability of common mode rejection for input signals
at potentials below that of the negative power supply rail;
3. Retention of the in phase relationship of the input and out-
put signals for input signals below the negative rail.
Although the CA3290 employs rugged bipolar (zener) diodes
for protection of the input circuit, the input terminal currents
should not exceed 1mA. Appropriate series connected
limiting resistors should be used in circuits where greater
current flows might exist, allowing the signal input voltage to
be greater than the supply voltage without damaging the
circuit.
Output Circuit
The output of the CA3290 is the open collector of an n-p-n
transistor, a feature providing flexibility in a broad range of
comparator applications. An output ORing function can be
implemented by parallel connection of the open collectors.
An output pull-up resistor can be connected to a power
supply having a voltage range within the rating of the
particular CA3290 in use; the magnitude of this voltage may
be set at a value which is independent of that applied to the
V+ terminal of the CA3290.
Parasitic Oscillations
The ideal comparator has, among other features, ultra high
input impedance, high gain, and wide bandwidth. These
desirable characteristics may, however, produce parasitic
oscillations unless certain precautions are observed to
minimize the stray capacitive coupling between the input and
output terminals. Parasitic oscillations manifest themselves
during the output voltage transition intervals as the
comparator switches states. For high source impedances,
stray capacitance can induce parasitic oscillations. The
addition of a small amount (1mV to 10mV) of positive
feedback (hysteresis) produces a faster transition, thereby
reducing the likelihood of parasitic oscillations. Furthermore,
if the input signal is a pulse waveform, with relatively rapid
rise and fall times, parasitic tendencies are reduced.
When dual comparators, like the CA3290, are packaged in an
8 lead configuration, the output terminal of each comparator is
adjacent to an input terminal. The lead-to-lead capacitance is
approximately 1pF, which may be sufficient to cause
undesirable feedback effects in certain applications. Circuit
factors such as impedance levels, supply voltage, switching
rate, etc., may increase the possibility of parasitic oscillations.
To minimize this potential oscillatory condition, it is
recommended that for source impedances greater than 1ka
capacitor (1pF - 2pF) be connected between the appropriate
input terminal and the output terminal. (See Figure 1.)
If either comparator is unused, its input terminals should also
be tied to either the V+ or V- supply rail.
Typical Applications
Light Controlled One-Shot Timer
In Figure 5 one comparator (A1) of the CA3290 is used to
sense a change in photo diode current. The other
comparator (A2) is configured as a one-shot timer and is
triggered by the output of A1. The output of the circuit will
switch to a low state for approximately 60 seconds after the
light source to the photo diode has been interrupted. The
circuit operates at normal room lighting levels. The
sensitivity of the circuit may be adjusted by changing the
values of R1 and R2. The ratio of R1 to R2 should be
constant to insure constant reverse voltage bias on the
photo diode.
R1 1.5M
+15V
+15V
+15V
15k
1M
15 +15V
k8
1N914
60M
3.3k
1.0µF
R2
2M
3+
A1 CA3290
2-
140k
1
+15V
5+
A2 CA3290
6-
7
C30809 4
0.01µF
1N914
10k
X 60s TIME
FIGURE 5. LIGHT CONTROLLED ONE-SHOT TIMER
5

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