MAX953ESA-T [MAXIM]
Operational Amplifier, 1 Func, 4000uV Offset-Max, CMOS, PDSO8, SO-8;
| 型号： | MAX953ESA-T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Operational Amplifier, 1 Func, 4000uV Offset-Max, CMOS, PDSO8, SO-8 放大器 光电二极管 |
| 文件： | 总12页 (文件大小：347K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0431; Rev 2; 8/01
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
General Description
Features
The MAX951–MAX954 feature combinations of a
micropower operational amplifier, comparator, and ref-
erence in an 8-pin package. In the MAX951 and
MAX952, the comparator’s inverting input is connected
to an internal 1.2V 2ꢀ bandgap reference. The
MAX953 and MAX954 are offered without an internal
reference. The MAX951/MAX952 operate from a single
2.7V to 7V supply with a typical supply current of 7µA,
while the MAX953/MAX954 operate from 2.4V to 7V with
a 5µA typical supply current. Both the op amp and
comparator feature a common-mode input voltage
range that extends from the negative supply rail to with-
in 1.6V of the positive rail, as well as output stages that
swing Rail-to-Rail®.
ꢀ Op Amp + Comparator + Reference in an 8-Pin
µMAX Package (MAX951/MAX952)
ꢀ 7µA Typical Supply Current
(Op Amp + Comparator + Reference)
ꢀ Comparator and Op Amp Input Range Includes
Ground
ꢀ Outputs Swing Rail-to-Rail
ꢀ 2.4V to 7V Supply Voltage Range
ꢀ Unity-Gain Stable and 125kHz Decompensated
A
V
≥ 10V/V Op Amp Options
ꢀ Internal 1.2V 2ꢀ ꢁandgap Reference
ꢀ Internal Comparator Hysteresis
The op amps in the MAX951/MAX953 are internally
compensated to be unity-gain stable, while the op
amps in the MAX952/MAX954 feature 125kHz typical
bandwidth, 66V/ms slew rate, and stability for gains of
10V/V or greater. These op amps have a unique output
stage that enables them to operate with an ultra-low
supply current while maintaining linearity under loaded
conditions. In addition, they have been designed to
exhibit good DC characteristics over their entire operat-
ing temperature range, minimizing input-referred errors.
ꢀ Op Amp Capable of Driving up to 1000pF Load
Selector Guide
INTERNAL
2ꢀ
PRECISION STAꢁILITY
OP AMP
GAIN
SUPPLY
CURRENT
(µA)
PART
COMPARATOR
REFERENCE
(V/V)
The comparator output stage of these devices continu-
ously sources as much as 40mA. The comparators
eliminate power-supply glitches that commonly occur
when changing logic states, minimizing parasitic feed-
back and making the devices easier to use. In addition,
they contain 3mV internal hysteresis to ensure clean
output switching, even with slow-moving input signals.
MAX951
MAX952
MAX953
MAX954
Yes
Yes
No
1
10
1
Yes
Yes
Yes
Yes
7
7
5
5
No
10
Pin Configuration
Applications
Instruments, Terminals, and Bar-Code Readers
Battery-Powered Systems
TOP VIEW
Automotive Keyless Entry
Low-Frequency, Local-Area Alarms/Detectors
Photodiode Preamps
1
2
3
4
8
AMPOUT
AMPIN-
AMPIN+
V
DD
7
6
5
COMPOUT
MAX951
MAX952
MAX953
MAX954
REF (COMPIN-)
COMPIN+
Smart Cards
V
SS
Infrared Receivers for Remote Controls
Smoke Detectors and Safety Sensors
DIP/SO/µMAX
(
) ARE FOR MAX953/MAX954
Typical Operating Circuit and Ordering Information appear
at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
AꢁSOLUTE MAXIMUM RATINGS
Supply Voltage (V
Inputs
to V )....................................................9V
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin µMAX (derate 4.10mW/°C above +70°C)...........330mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)........640mW
Operating Temperature Ranges
DD
SS
Current (AMPIN_, COMPIN_)..........................................20mA
Voltage (AMPIN_, COMPIN_).......(V + 0.3V) to (V - 0.3V)
DD
SS
Outputs
MAX95_E_A.....................................................-40°C to +85°C
MAX95_MJA ..................................................-55°C to +125°C
Maximum Junction Temperatures
MAX95_E_A .................................................................+150°C
MAX95_MJA.................................................................+175°C
Storage Temperature Range.............................-65°C to +165°C
Lead Temperature (soldering, 10s) .................................+300°C
Current (AMPOUT, COMPOUT)......................................50mA
Current (REF) ..................................................................20mA
Voltage (AMPOUT, COMPOUT,
REF)...................................(V + 0.3V) to (V - 0.3V)
DD
SS
Short-Circuit Duration (REF, AMPOUT)..................Continuous
Short-Circuit Duration (COMPOUT, V
Continuous Power Dissipation (T = +70°C)
to V ≤ 7V)......1min
DD
SS
A
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ...727mW
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
= 2.8V to 7V for MAX951/MAX952, V
= 2.4V to 7V for MAX953/MAX954, V = 0, V
= 0 for the MAX953/MAX954,
CM COMP
DD
DD
SS
V
= 0, AMPOUT = (V
+ V )/2, COMPOUT = low, T = T
to T
, typical values are at T = +25°C, unless
MAX A
CM OPAMP
DD
SS
A
MIN
otherwise noted.)
PARAMETER
SYMꢁOL
CONDITIONS
MIN
2.8
2.7
2.4
TYP
MAX
7.0
7.0
7.0
10
11
13
8
UNITS
T
A
T
A
= T
to T
MIN MAX
MAX951/MAX952
Supply Voltage Range
V
DD
= -10°C to +85°C
V
MAX953/MAX954
= +25°C, MAX951/MAX952
T
A
7
5
MAX951E/MAX952E
MAX951M/MAX952M
Supply Current
(Note 1)
I
S
µA
T
A
= +25°C, MAX953/MAX954
MAX953E/MAX954E
MAX953M/MAX954M
9
11
COMPARATOR
T
= +25°C
1
3
14
14
6
A
MAX95_EPA/ESA
MAX95_EUA (µMAX)
MAX95_MJA
Input Offset Voltage
(Note 2)
V
OS
mV
T
= +25°C
4
17
A
MAX95_EUA (µMAX)
MAX95_EPA/ESA
MAX95_MJA
Trip Point
(Note 3)
mV
nA
5
7
T
= +25°C
0.003
0.003
0.050
5
A
Input Leakage Current
(Note 4)
MAX95_E
MAX95_M
40
Common-Mode Input Range
CMVR
CMRR
V
SS
V
DD
-1.6V
1
V
Common-Mode Rejection Ratio
V
SS
to (V
- 1.6V), MAX953/MAX954
0.1
mV/V
DD
2
_______________________________________________________________________________________
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
= 2.8V to 7V for MAX951/MAX952, V
= 2.4V to 7V for MAX953/MAX954, V = 0, V
= 0 for the MAX953/MAX954,
CM COMP
DD
DD
SS
V
= 0, AMPOUT = (V
+ V )/2, COMPOUT = low, T = T
to T
, typical values are at T = +25°C, unless
MAX A
CM OPAMP
DD
SS
A
MIN
otherwise noted.)
PARAMETER
SYMꢁOL
CONDITIONS
MIN
TYP
0.05
0.05
22
MAX
UNITS
MAX951/MAX952, V
= 2.8V to 7V
1
1
DD
DD
Power-Supply Rejection Ratio
Response Time
PSRR
mV/V
MAX953/MAX954, V
= 2.4V to 7V
V
= 10mV
OD
OD
C = 100pF, T
=
A
L
t
pd
µs
+25°C, V - V = 5V
DD
SS
V
= 100mV
4
Output High Voltage
Output Low Voltage
REFERENCE
V
I
I
= 2mA
V - 0.4V
DD
V
V
OH
SOURCE
V
= 1.8mA
V + 0.4V
SS
OL
SINK
MAX95_EPA/ESA
MAX95_EUA (µMAX)
MAX95_MJA
1.176
1.130
1.164
1.200
1.200
1.200
0.1
1.224
1.270
1.236
Reference Voltage
(Note 5)
V
REF
V
I
I
I
=
=
=
20µA, T = +25°C
OUT
OUT
OUT
A
Load Regulation
6µA, MAX95_E
3µA, MAX95_M
1.5
1.5
%
Voltage Noise
e
n
0.1Hz to 10Hz
16
1
µV
P-P
OP AMP
T
A
= +25°C
3
MAX95_EPA/ESA
MAX95_EUA (µMAX)
MAX95_MJA
4
5
Input Offset Voltage
Input Bias Current
V
mV
OS
5
T
A
= +25°C
0.003
0.003
0.003
1000
0.050
5
I
MAX95_E
MAX95_M
nA
B
40
T
= +25°C
100
50
10
40
25
5
A
Large-Signal Gain
(No Load)
AMPOUT = 0.5V to
A
A
MAX95_E
MAX95_M
V/mV
V/mV
VOL
4.5V, V
- V = 5V
DD
SS
T
A
= +25°C
150
Large-Signal Gain
AMPOUT = 0.5V to
4.5V, V - V = 5V
MAX95_E
MAX95_M
VOL
(100kΩ Load to V
)
SS
DD
SS
A
= 1V/V, MAX951/MAX953, V
- V = 5V
20
125
12.5
66
V
DD
SS
Gain Bandwidth
Slew Rate
GBW
SR
kHz
A = 10V/V, MAX952/MAX954, V - V = 5V
V
V
DD
DD
SS
A
= 1V/V, MAX951/MAX953, V
- V = 5V
SS
V/ms
A = 10V/V, MAX952/MAX954, V - V = 5V
V
DD
SS
Common-Mode Input Range
CMVR
CMRR
V
SS
V
DD
- 1.6
1
V
Common-Mode Rejection Ratio
V
V
V
= V to (V - 1.6V)
DD
0.03
0.07
0.07
80
mV/V
CM OPAMP
SS
= 2.8V to 7V, MAX951/MAX952
= 2.4V to 7V, MAX953/MAX954
1.0
1.0
DD
DD
Power-Supply Rejection Ratio
PSRR
mV/V
f = 1kHz
o
nV√Hz
Input Noise Voltage
e
n
f = 0.1Hz to 10Hz
o
1.2
µV
P-P
_______________________________________________________________________________________
3
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
= 2.8V to 7V for MAX951/MAX952, V
= 2.4V to 7V for MAX953/MAX954, V = 0, V
= 0 for the MAX953/MAX954,
CM COMP
DD
DD
SS
V
= 0, AMPOUT = (V
+ V )/2, COMPOUT = low, T = T
to T
, typical values are at T = +25°C, unless
MAX A
CM OPAMP
DD
SS
A
MIN
otherwise noted.)
PARAMETER
SYMꢁOL
CONDITIONS
MIN
TYP
V
MAX
UNITS
Output High Voltage
Output Low Voltage
V
OH
R = 100kΩ to V
V
- 500mV
V
V
L
SS
SS
DD
V
OL
R = 100kΩ to V
+ 50mV
SS
L
T
T
= +25°C
70
A
A
= +25°C, V
- V = 5V
300
60
820
DD
DD
SS
Output Source Current
Output Sink Current
I
µA
SRC
SNK
MAX95_E
MAX95_M
40
T
A
T
A
= +25°C
70
= +25°C, V
- V = 5V
200
50
570
µA
SS
I
MAX95_E
MAX95_M
30
Note 1: Supply current is tested with COMPIN+ = (REF - 100mV) for MAX951/MAX952, and COMPIN+ = 0 for MAX953/MAX954.
Note 2: Input Offset Voltage is defined as the center of the input-referred hysteresis. V = REF for MAX951/MAX952, and
CM COMP
V
= 0 for MAX953/MAX954.
CM COMP
Note 3: Trip Point is defined as the differential input voltage required to make the comparator output change. The difference
between upper and lower trip points is equal to the width of the input-referred hysteresis. V = REF for
CM COMP
MAX951/MAX952, and V
= 0 for MAX953/MAX954.
CM COMP
Note 4: For MAX951/MAX952, input leakage current is measured for COMPIN- at the reference voltage. For MAX953/MAX954, input
leakage current is measured for both COMPIN+ and COMPIN- at V
.
SS
Note 5: Reference voltage is measured with respect to V . Contact factory for availability of a 3% accurate reference voltage in the
SS
µMAX package.
4
________________________________________________________________________________________
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
SUPPLY CURRENT
vs. TEMPERATURE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
REFERENCE VOLTAGE vs. TEMPERATURE
1.220
1.215
1.210
1.205
1.200
10
9
9
8
8
7
7
MAX951/MAX952
6
MAX951/MAX952
6
5
4
3
2
1
0
5
MAX953/MAX954
4
3
2
1
0
MAX953/MAX954
1.195
1.190
V
= 0
DD
CM OPAMP
V
= 2.8V (MAX951/952), V = 2.4V
DD
DD
CM OPAMP
AMPOUT = (V + V )/2
SS
(MAX953/954), V = 0, V
= 0
SS
DD
COMP- = 1.2V or REF
COMP+ = 1.1V
V
= 5V
0
1.185
1.180
DD
AMPOUT = 1/2 V , COMP- = 1.2V or REF
COMP+ = 1.1V
-60 -40 -20
20 40 60 80 100 120 140
-60 -40 -20
0
20 40 60 80 100 120 140
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
DC OPEN-LOOP GAIN vs.
SUPPLY VOLTAGE
REFERENCE OUTPUT VOLTAGE
vs. LOAD CURRENT
7
1x10
1.30
80
70
60
V
DD
= 2.0 to 3.0V, V = -2.5V
SS
V
= 5V
SUPPLY
NONINVERTING
AMPIN+ = 0
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10
6
1x10
A
CL
= 1V/V (MAX951/2)
= 10V/V (MAX953/4),
COMP- = 1.2V or REF
CL
SINKING CURRENT
5
A
1x10
50
40
COMP+ = 1.1V from V
SS
4
1x10
A
3
1x10
C
30
20
2
1x10
B
SOURCING CURRENT
A: MAX951/952 REF
10 B: MAX951/953 OP AMP
1
1x10
1mHz INPUT SIGNAL
= 100kΩ
C: MAX952/954 OP AMP
0
R
L
0
1x10
1
10
100
1k
10k 100k
1M
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
1
10
100
FREQUENCY (Hz)
LOAD CURRENT (µA)
MAX952/MAX954
OPEN-LOOP GAIN AND PHASE
MAX951/MAX953
OPEN-LOOP GAIN AND PHASE
vs. FREQUENCY
DC OPEN-LOOP GAIN
vs. TEMPERATURE
vs. FREQUENCY
MAX951-954-toc08
MAX951-954-toc09
6
5
4
3
2
0
100
80
1x10
1x10
1x10
1x10
1x10
100
80
0
-60
-60
PHASE
60
PHASE
-120
-180
-240
60
40
20
0
-120
-180
-240
-300
-360
GAIN
40
GAIN
20
0
V
= 5V
-300
-360
DD
1
0
1x10
1x10
1MHz INPUT SIGNAL
= 100kΩ
R
= 100kΩ
R
= 100kΩ
L
L
R
L
-20
-20
1
10
100
1k
10k 100k 1M
-60 -40 -20
0
20 40 60 80 100 120 140
1
10
100
1k
10k
100k 1M
FREQUENCY (Hz)
TEMPERATURE (°C)
FREQUENCY (Hz)
__________________________________________________________________________________________________ 5
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
OP AMP OUTPUT VOLTAGE
vs. LOAD CURRENT
OP AMP SHORT-CIRCUIT CURRENT
vs. SUPPLY VOLTAGE
0.10
0.08
2000
1500
1000
500
NONINVERTING
A, D: V
B, E: V
C, F: V
=
=
=
1.5V
2.5V
3.5V
SUPPLY
SUPPLY
SUPPLY
AMPIN+ = (V - V )/2
DD SS
C
A
B
0.06
0.04
SINKING CURRENT
0.02
SHORT TO V
SS
0.10
-0.02
-0.04
-0.06
-0.08
-0.10
SOURCING CURRENT
0
E
F
D
SHORT TO V
DD
-500
NONINVERTING
AMPIN+ = GND
-1000
2.5
3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
3.0
1
10
100
1000 2000
LOAD CURRENT (µA)
OP AMP PERCENT OVERSHOOT
vs. CAPACITIVE LOAD
COMPARATOR OUTPUT VOLTAGE
vs. LOAD CURRENT
100
90
80
70
60
50
40
30
20
10
0
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
PARTS–V
SUPPLY
A: MAX951/952, 3V
SOURCING CURRENT
B: MAX951/953, 5V
D: MAX952/954, 3V
E: MAX952/954, 5V
MAX951/953, A = 1V/V
C
E
MAX952/954, A
= 10V/V
AMPOUT = 1V
D
B
P-P
V
= (V - V /2)
CM
DD SS
A
V
= 5V
SUPPLY
SINKING CURRENT
1
2
3
4
5
6
10
10
10
10
10
10
0.01
0.1
1
10
100 200
CAPACITIVE LOAD (pF)
LOAD CURRENT (mA)
COMPARATOR SHORT-CIRCUIT
CURRENT vs. SUPPLY VOLTAGE
250
200
150
100
SOURCING CURRENT
SINKING CURRENT
50
0
-50
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
SUPPLY VOLTAGE (V)
6
________________________________________________________________________________________
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
COMPARATOR RESPONSE TIME
COMPARATOR RESPONSE TIME
FOR VARIOUS INPUT OVERDRIVES (FALLING)
FOR VARIOUS INPUT OVERDRIVES (RISING)
MAX951-954 TOC16
INPUT
100mV/div
0
OUTPUT
1V/div
100mV
100mV
OUTPUT
1V/div
10mV
20mV
10mV
50mV
20mV
50mV
0
0
INPUT
100mV/div
0
2µs/div
MAX953: LOAD = 100kΩ || 100pF, V
2µs/div
MAX953: LOAD = 100kΩ || 100pF, V
= 5V
SUPPLY
= 5V
SUPPLY
MAX951/MAX953 OP AMP
SMALL-SIGNAL TRANSIENT RESPONSE
MAX951/MAX953 OP AMP
LARGE-SIGNAL TRANSIENT RESPONSE
INPUT
2V/div
INPUT
200mV/div
OUTPUT
1V/div
OUTPUT
50mV/div
2.5V
2.5V
200µs/div
100µs/div
NONINVERTING, A = 1V/V,
VCL
NONINVERTING: A = 1V/V,
VCL
LOAD = 100kΩ || 100pF to V , V
= 5V
SS SUPPLY
LOAD = 100kΩ || 100pF to V , V
= 5V
SS SUPPLY
MAX952/MAX954 OP AMP
LARGE-SIGNAL TRANSIENT RESPONSE
MAX952/MAX954 OP AMP
SMALL-SIGNAL TRANSIENT RESPONSE
INPUT
20mV/div
INPUT
200mV/div
OUTPUT
1V/div
OUTPUT
50mV/div
2.5V
2.5V
100µs/div
100µs/div
NONINVERTING, A = 10V/V,
NONINVERTING, A = 10V/V,
VCL
VCL
LOAD = 100kΩ || 100pF to V , V
= 5V
LOAD = 100kΩ || 100pF to V , V
= 5V
SS SUPPLY
SS SUPPLY
__________________________________________________________________________________________________ 7
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
Pin Description
PIN
NAME
FUNCTION
MAX951
MAX952
MAX953
MAX954
1
2
1
2
AMPOUT
AMPIN-
Op Amp Output
Inverting Op Amp Input
Noninverting Op Amp Input
Negative Supply or Ground
Noninverting Comparator Input
3
3
AMPIN+
4
4
V
SS
5
5
COMPIN+
REF
6
—
6
1.200V Reference Output. Also connected to inverting comparator input.
—
7
COMPIN-
COMPOUT
Inverting Comparator Input
Comparator Output
Positive Supply
7
8
8
V
DD
Functional Diagrams
AMPOUT
OP AMP
V
8
7
DD
8
1
V
DD
AMPOUT
OP AMP
COMPOUT
MAX953
MAX954
1
2
3
AMPIN-
AMPIN+
COMPOUT
COMPIN-
7
6
x1
2
3
AMPIN-
AMPIN+
REF
6
5
1.20V
4
V
SS
COMP
COMP
4
COMPIN+
5
V
SS
COMPIN+
MAX951
MAX952
Figure 1. MAX951–MAX954 Functional Diagrams
high-impedance differential inputs and a common-
mode input voltage range that extends from the nega-
tive supply rail to within 1.6V of the positive rail. They
have a CMOS output stage that swings rail to rail and is
driven by a proprietary high gain stage, which enables
them to operate with an ultra-low supply current while
maintaining linearity under loaded conditions. Careful
design results in good DC characteristics over their
entire operating temperature range, minimizing input
referred errors.
Detailed Description
The MAX951–MAX954 are combinations of a micropow-
er op amp, comparator, and reference in an 8-pin pack-
age, as shown in Figure 1. In the MAX951/MAX952, the
comparator’s negative input is connected to a 1.20V
2% bandgap reference. All four devices are optimized
to operate from a single supply. Supply current is less
than 10µA (7µA typical) for the MAX951/MAX952 and
less than 8µA (5µA typical) for the MAX953/MAX954.
Op Amp
The op amps in the MAX951/MAX953 are internally
compensated to be unity-gain stable, while the op
amps in the MAX952/MAX954 feature 125kHz typical
gain bandwidth, 66V/ms slew rate, and stability for
gains of 10V/V or greater. All these op amps feature
Comparator
The comparator in the MAX951–MAX954 has a high-
impedance differential input stage with a common-
mode input voltage range that extends from the
negative supply rail to within 1.6V of the positive rail.
Their CMOS output stage swings rail-to-rail and can
8
_______________________________________________________________________________________
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
R2
R2
RA
R1
V
V
S
IN
COMPOUT
COMPOUT
RB
REF
REF
Figure 2. External Hysteresis
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.
Comparator Hysteresis
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:
The MAX951–MAX954 comparator outputs swing rail-
to-rail (from V
to V ). TTL compatibility is assured
SS
DD
1) Set R2. The leakage current in COMPIN+ is less
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
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
upper trip point is V
/R2 or 500nA.
REF
2) Choose the width of the hysteresis band. In this
V
= 5V) for short pulses, as long as the package’s
DD
example choose V
= 50mV.
EHYST
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.
V
− 2V
[
]
EHYST
IHYST
R1= R2
V
+ 2V
IHYST
(
)
DD
where the internal hysteresis is V
= 3mV.
IHYST
Reference
The internal reference in the MAX951/MAX952 has an
3) Determine R1. If the supply voltage is 5V, then R1 =
output of 1.20V with respect to V . Its accuracy is 2%
SS
24kΩ.
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.
4) Check the hysteresis trip points. The upper trip point is
R1 + R2
(
)
V
=
V
+ V
(
)
IN(H)
REF IHYST
R2
or 1.22V in our example. The lower trip point is 50mV
less, or 1.17V in our example.
Applications Information
If a resistor divider is used for R1, the calculations
should be modified using a Thevenin equivalent
model.
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.
5) Determine R :
A
_______________________________________________________________________________________
9
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
V
= 5V
CC
ANTENNA
AMPIN+
0.1µF
20kΩ
MAX952
0.1µF
AMPOUT
10MΩ
C1
A
390pF
AMP
L1
C1
B
330pF
330mH
R2
1MΩ
C1
C
COMP
1.2V
100kΩ
20pF to
60pF
R1
5.1MΩ
1
REF
L1 x C1 =
2
(2πf )
C
2pF to 10pF
LAYOUT-SENSITIVE AREA,
METAL RFI SHIELDING ADVISED
Figure 3. Compensation for Feedback-Node Capacitance
Figure 4. Low-Frequency Radio Receiver Application
Op Amp Stability and Board Layout
Considerations
V
SHYST
R
≈ R2
, for V
>> V
A
SHYST IHYST
V
DD
Unlike other industry-standard micropower CMOS
op amps, the op amps in the MAX951–MAX954 main-
tain stability in their minimum gain configuration while
driving heavy capacitive loads, as demonstrated in the
MAX951/MAX953 Op Amp Percent Overshoot vs.
Capacitive Load graph in the Typical Operating
Characteristics.
In the example, R is again 24kΩ.
6) Select the upper trip point V
at 4.75V.
A
. Our example is set
S(H)
7) Calculate R .
B
V
+ V
IHYST
R2 R
(
) ( )(
)
A
REF
A
Although this family is primarily designed for low-
frequency applications, good layout is extremely impor-
tant. Low-power, high-impedance circuits may increase
the effects of board leakage and stray capacitance. For
example, the combination of a 10MΩ resistance (from
leakage between traces on a contaminated, poorly
designed PC board) and a 1pF stray capacitance
provides a pole at approximately 16kHz, which is near
the amplifier’s bandwidth. Board routing and layout
should minimize leakage and stray capacitance. In
some cases, stray capacitance may be unavoidable
and it may be necessary to add a 2pF to 10pF capaci-
tor across the feedback resistor to compensate; select
the smallest capacitor value that ensures stability.
R
=
B
R2 V
− V
+ V
R
+ R2
(
)
(
)(
)
S H
( )
REF
IHSYT
where R is 8.19kΩ, or approximately 8.2kΩ.
B
Input Noise Considerations
Because low power requirements often demand high-
impedance circuits, effects from radiated noise are more
significant. Thus, traces between the op amp or com-
parator inputs and any resistor networks attached should
be kept as short as possible.
Crosstalk
Reference
Internal crosstalk to the reference from the comparator
is package dependent. Typical values (V
45mV for the plastic DIP package and 32mV for the SO
package. Applications using the reference for the op
amp or external circuitry can eliminate this crosstalk by
usinga simple RC lowpass filter, as shown inFigure 5.
Input Overdrive
With 100mV overdrive, comparator propagation delay
is typically 6µs. The Typical Operating Characteristics
show propagation delay for various overdrive levels.
= 5V) are
DD
Supply current can increase when the op amp in the
MAX951–MAX954 is overdriven to the negative supply rail.
For example, when connecting the op amp as a compara-
tor and applying a -100mV input overdrive, supply current
rises by around 15µA and 32µA for supply voltages of
2.8V and 7V, respectively.
Op Amp
Internal crosstalk to the op amp from the comparator is
package dependent, but not input-referred. Typical
values (V
= 5V) are 4mV for the plastic DIP package
DD
and 280µV for the SO package.
10 _______________________________________________________________________________________
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
V
= 5V
CC
MAX953
C2
15pF, 5%
10kHz
5V
P-P
V
CC
NEC
R2
NEC
SE307-C
PH302B
1.0MΩ,1%
0.1µF
30kΩ
4.7MΩ
RADIOACTIVE
IONIZATION
10MΩ
51Ω
R1
A
AMP
C1
AMP
CHAMBER
49.9kΩ, 1%
150pF, 5%
SMOKE SENSOR
COMP
R1
B
49.9kΩ, 1%
COMP
100kΩ
1.2V
LAYOUT-SENSITIVE AREA
0.1µF
MAX952
5.1MΩ
REF
LAYOUT-SENSITIVE AREA
1
R1 x C1 = R2 x C2 =
2π f
C
Figure 5. Infrared Receiver Application
Figure 6. Sensor Preamp and Alarm Trigger Application
receiver. The op amp is configured as a Delyiannis-
Friend bandpass filter to reduce disturbances from
noise and eliminate low-frequency interference from
sunlight, fluorescent lights, etc. This circuit is applica-
ble for TV remote controls and low-frequency data links
up to 20kbps. Carrier frequencies are limited to around
10kHz. 10kHz is used in the example circuit.
Power-Supply Bypassing
Power-supply bypass capacitors are not required if the
supply impedance is low. For single-supply applications,
it is good general practice to bypass V
with a. 0.1µF
DD
capacitor to ground. Do not bypass the reference output.
Applications Circuits
Component layout and routing for the amplifier should
be tight to reduce stray capacitance, 60Hz interfer-
ence, and RFI from the comparator. Crosstalk from
comparator edges will distort the amplifier signal. In
order to minimize the effect, a lowpass RC filter is
added to the connection from the reference to the non-
inverting input of the op amp.
Low-Frequency Radio Receiver for
Alarms and Detectors
The circuit in Figure 4 is useful as a front end for low-
frequency RF alarms. The unshielded inductor (M7334-
ND from Digikey) is used with capacitors C1 , C1 , and
A
B
C1 in a resonant circuit to provide frequency selectivity.
C
The op amp from a MAX952 amplifies the signal
received. The comparator improves noise immunity,
provides a signal strength threshold, and translates the
received signal into a pulse train. Carrier frequencies are
limited to around 10kHz. 10kHz is used in the example in
Figure 4.
Sensor Preamp and Alarm Trigger for
Smoke Detectors
The high-impedance CMOS inputs of the MAX951–
MAX954 op amps are ideal for buffering high-imped-
ance sensors, such as smoke detector ionization cham-
bers, piezoelectric transducers, gas detectors, and pH
sensors. Input bias currents are typically less than 3pA
at room temperature. A 5µA typical quiescent current
for the MAX953 will minimize battery drain without
resorting to complex sleep schemes, allowing continu-
ous monitoring and immediate detection.
The layout and routing of components for the amplifier
should be tight to minimize 60Hz interference and
crosstalk from the comparator. Metal shielding is
recommended to prevent RFI from the comparator or
digital circuitry from exciting the receiving antenna. The
transmitting antenna can be long parallel wires spaced
about 7.2cm apart, with equal but opposite currents.
Radio waves from this antenna will be detectable when
the receiver is brought within close proximity, but
cancel out at greater distances.
Ionization-type smoke detectors use a radioactive source,
such as Americium, to ionize smoke particles. A positive
voltage on a plate attached to the source repels the posi-
tive smoke ions and accelerates them toward an outer
electrode connected to ground. Some ions collect on an
intermediate plate. With careful design, the voltage on this
plate will stabilize at a little less than one-half the supply
voltage under normal conditions, but rise higher when
smoke increases the ion current. This voltage is buffered
Infrared Receiver Front End for
Remote Controls and Data Links
The circuit in Figure 5 uses the MAX952 as a pin photo-
diode preamplifier and discriminator for an infrared
______________________________________________________________________________________ 11
Ultra-Low-Power, Single-Supply
Op Amp + Comparator + Reference
by the high-input-impedance op amp of a MAX951
(Figure 6). The comparator and resistor voltage divider
set an alarm threshold to indicate a fire.
Chip Topography
V
DD
AMPOUT
Design and fabrication of the connection from the inter-
mediate plate of the ionization chamber to the nonin-
verting input of the op amp is critical, since the
AMPIN-
COMPOUT
impedance of this node must be well above 50MΩ. This
connection must be as short and direct as possible to
prevent charge leakage and 60Hz interference. Where
0.084"
(2.134mm)
possible, the grounded outer electrode or chassis of
the ionization chamber should shield this connection to
reduce 60Hz interference. Pay special attention to
board cleaning, to prevent leakage due to ionic com-
pounds such as chlorides, flux, and other contaminants
from the manufacturing process. Where applicable, a
coating of high-purity wax may be used to insulate this
connection and prevent leakage due to surface mois-
ture or an accumulation of dirt.
AMPIN+
REF(COMPIN-)
COMPIN+
V
SS
0.058"
(1.473mm)
(
) ARE FOR MAX953/MAX954
Ordering Information
Chip Information
PART
TEMP RANGE
0°C to +70°C
PIN-PACKAGE
Dice*
TRANSISTOR COUNT: 163
SUBSTRATE CONNECTED TO V
MAX951C/D
MAX951EPA
MAX951ESA
MAX951EUA
MAX951MJA
MAX952C/D
MAX952EPA
MAX952ESA
MAX952EUA
MAX952MJA
MAX953C/D
MAX953EPA
MAX953ESA
MAX953EUA
MAX953MJA
MAX954C/D
MAX954EPA
MAX954ESA
MAX954EUA
MAX954MJA
DD
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
8 Plastic Dip
8 SO
__________Typical Operating Circuit
8 µMAX
8 CERDIP**
Dice*
8
V
CC
0.1µF
INPUT
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
8 Plastic Dip
8 SO
AMPIN+
3
8 µMAX
MAX951
MAX952
2
8 CERDIP**
Dice*
1
5
6
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
8 Plastic Dip
8 SO
1MΩ
COMPOUT
7
R2
R1
8 µMAX
8 CERDIP**
Dice*
REF
4
1.20V
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
8 Plastic Dip
8 SO
V
SS
8 µMAX
8 CERDIP**
Package Information
For the latest package outline information, go to
*Dice are tested at T = +25°C, DC parameters only.
A
**Contact factory for availability and processing to MIL-STD-883.
www.maxim-ic.com/packages.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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