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AP393
Low Power Low Offset Voltage Dual Comparators
Application Information
The AP393 is high gain, wide bandwidth devices
which, like most comparators, can easily oscillate if
the output lead is inadvertently allowed to
capacitively couple to the inputs via stray
capacitance. This shows up only during the output
voltage transition intervals as the comparator
change states. Power supply bypassing is not
required to solve this problem. Standard PC board
layout is helpful as it reduces stray input-output
coupling. Reducing the input resistors to < 10k
reduces the feedback signal levels and finally,
adding even a small amount (1.0 to 10 mV) of
positive feedback (hysteresis) causes such a rapid
transition that oscillations due to stray feedback are
not possible. Simply socketing the IC and attaching
resistors to the pins will cause input-output
oscillations during the small transition intervals
unless hysteresis is used. If the input signal is a
pulse waveform, with relatively fast rise and fall
times, hysteresis is not required. All input pins of
any unused comparators should be tied to the
negative supply.
The bias network of the AP393 establishes a drain
current which is independent of the magnitude of
the power supply voltage over the range of from 2.0
V
DC
to 30 V
DC
. It is usually unnecessary to use a
bypass capacitor across the power supply line.
The differential input voltage may be larger than V+
without damaging the device (Note 8). Protection
Marking Information
Anachip Corp.
www.anachip.com.tw Rev. 1.0 Sep 7, 2004
11/13
should be provided to prevent the input voltages
from going negative more than -0.3 V
DC
(at 25°C).
An input clamp diode can be used as shown in the
applications section.
The output of the AP393 is the uncommitted
collector of a grounded-emitter NPN output
transistor. Many collectors can be tied together to
provide an output OR’ing function. An output pull-up
resistor can be connected to any available power
supply voltage within the permitted supply voltage
range and there is no restriction on this voltage due
to the magnitude of the voltage which is applied to
the V
terminal of the AP393 package. The output
can also be used as a simple SPST switch to
ground (when a pull-up resistor is not used). The
amount of current which the output device can sink
is limited by the drive available (which is
independent of V
) and the
β
of this device. When
the
maximum
current
(approximately 16mA), the output transistor will
come out of saturation and the output voltage will
rise very rapidly. The output saturation voltage is
limited by the approximately 60
r
SAT
of the output
transistor. The low offset voltage of the output
transistor (1.0 mV) allows the output to clamp
essentially to ground level for small load currents.
limit
is
reached
(Top View)
SOP-8L/PDIP-8L
AP393
YY WW X
Logo
Part No.
ID code: internal
Year: "01" =2001
"02" =2002
Xth week: 01~52
~
5
8
4
1