MAX954ESA Maxim Integrated Products, MAX954ESA Datasheet - Page 9

• Manufacturer Part Number: MAX954ESA
• Description: Op Amps Op Amp / Comparator / Reference
• Manufacturer: Maxim Integrated Products

Specifications of MAX954ESA

• Lead Free Status / Rohs Status: No

continuously source as much as 40mA. The compara-
tors eliminate power-supply glitches that commonly
occur when changing logic states, minimizing parasitic
feedback and making them easier to use. In addition,
they include internal hysteresis (±3mV) to ensure clean
output switching, even with slow-moving input signals.
The inputs can be taken above and below the supply
rails up to 300mV without damage. Input voltages
beyond this range can forward bias the ESD-protection
diodes and should be avoided.
The MAX951–MAX954 comparator outputs swing rail-
to-rail (from V
by using a 5V ±10% supply.
The MAX951–MAX954 comparators continuously output
source currents as high as 40mA and sink currents of
over 5mA, while keeping quiescent currents in the
microampere range. The output can source 100mA (at
V
maximum power dissipation is not exceeded. The out-
put stage does not generate crowbar switching currents
during transitions; this minimizes feedback through the
supplies and helps ensure stability without bypassing.
The internal reference in the MAX951/MAX952 has an
output of 1.20V with respect to V
in the -40°C to +85°C temperature range. It is comprised
of a trimmed bandgap reference fed by a proportional-
to-absolute-temperature (PTAT) current source and
buffered by a micropower unity-gain amplifier. The REF
output is typically capable of sourcing and sinking 20µA.
Do not bypass the reference output. The reference is
stable for capacitive loads less than 100pF.
The micropower MAX951–MAX954 are designed to
extend battery life in portable instruments and add
functionality in power-limited industrial controls.
Following are some practical considerations for circuit
design and layout.
Figure 2. External Hysteresis
DD
= 5V) for short pulses, as long as the package’s
V
IN
DD
Applications Information
to V
R1
_______________________________________________________________________________________
SS
). TTL compatibility is assured
REF
Op Amp + Comparator + Reference
SS
R2
. Its accuracy is ±2%
Ultra-Low-Power, Single-Supply
Reference
COMPOUT
Hysteresis increases the comparator’s noise immunity
by increasing the upper threshold and decreasing the
lower threshold. The comparator in these devices con-
tain a ±3mV wide internal hysteresis band to ensure
clean output switching, even with slow-moving signals.
When necessary, hysteresis can be increased by using
external resistors to add positive feedback, as shown in
Figure 2. This circuit increases hysteresis at the
expense of more supply current and a slower
response. The design procedure is as follows:
1) Set R2. The leakage current in COMPIN+ is less
2) Choose the width of the hysteresis band. In this
3) Determine R1. If the supply voltage is 5V, then R1 =
4) Check the hysteresis trip points. The upper trip point is
5) Determine R
than 5nA (up to +85°C), so current through R2 can
be as little as 500nA and still maintain good accura-
cy. If R2 = 2.4MΩ, the current through R2 at the
upper trip point is V
example choose V
where the internal hysteresis is V
24kΩ.
or 1.22V in our example. The lower trip point is 50mV
less, or 1.17V in our example.
If a resistor divider is used for R1, the calculations
should be modified using a Thevenin equivalent
model.
V
S
V
IN H
RA
( )
R1 R2
RB
=
=
A
:
(
R1 + R2
[
R2
V
EHYST
(
EHYST
REF
V
DD
REF
Comparator Hysteresis
/R2 or 500nA.
)
+
= 50mV.
(
V
−
REF
2
R2
V
2
IHYST
V
IHYST
+
IHYST
V
)
IHYST
]
= 3mV.
COMPOUT
)
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