MAXIM MAX4091, MAX4092, MAX4094 Technical data

General Description
The single MAX4091, dual MAX4092, and quad MAX4094 operational amplifiers combine excellent DC accuracy with Rail-to-Rail®operation at the input and output. Since the common-mode voltage extends from VCCto VEE, the devices can operate from either a sin­gle supply (2.7V to 6V) or split supplies (±1.35V to ±3V). Each op amp requires less than 130µA of supply current. Even with this low current, the op amps are capable of driving a 1kload, and the input-referred voltage noise is only 12nV/Hz. In addition, these op amps can drive loads in excess of 2000pF.
The precision performance of the MAX4091/MAX4092/ MAX4094 combined with their wide input and output dynamic range, low-voltage, single-supply operation, and very low supply current, make them an ideal choice for battery-operated equipment, industrial, and data acquisition and control applications. In addition, the MAX4091 is available in space-saving 5-pin SOT23, 8-pin µMAX, and 8-pin SO packages. The MAX4092 is available in 8-pin µMAX and SO packages, and the MAX4094 is available in 14-pin TSSOP and 14-pin SO packages.
________________________Applications
Portable Equipment
Battery-Powered Instruments
Data Acquisition and Control
Low-Voltage Signal Conditioning
Features
Low-Voltage, Single-Supply Operation (2.7V to 6V)
Beyond-the-Rails™ Inputs
No Phase Reversal for Overdriven Inputs
30µV Offset VoltageRail-to-Rail Output Swing with 1kLoad
Unity-Gain Stable with 2000pF Load
165µA (max) Quiescent Current Per Op Amp
500kHz Gain-Bandwidth Product
High Voltage Gain (115dB)
High Common-Mode Rejection Ratio (90dB) and
Power-Supply Rejection Ratio (100dB)
Temperature Range (-40°C to +125°C)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
________________________________________________________________ Maxim Integrated Products 1
Pin Configurations/Functional Diagrams
19-2272; Rev 0; 1/02
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.
Ordering Information
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. Beyond-the-Rails is a trademark of Maxim Integrated Products, Inc.
PART TEMP RANGE PIN-PACKAGE
MAX4091AUK-T -40°C to +125°C 5 SOT23-5
MAX4091ASA -40°C to +125°C 8 SO
MAX4091AUA -40°C to +125°C 8 µMAX
MAX4092ASA -40°C to +125°C 8 SO
MAX4092AUA -40°C to +125°C 8 µMAX
MAX4094AUD -40°C to +125°C 14 TSSOP
MAX4094ASD -40°C to +125°C 14 SO
TOP VIEW
N.C.
IN+
V
OUT
1
MAX4091 MAX4092
IN-
2
3
4
EE
µMAX/SO
N.C.
8
V
CC
7
OUT
6
N.C.
5
V
IN+
1
MAX4091
EE
2
3
SOT23
5
4
4
OUT1
V
CC
IN-
IN1-
IN1+
V
1
2
3
4
EE
µMAX/SO
OUT1
1
IN1-
IN1+
V
IN2+
IN2-
OUT2
2
3
CC
4
MAX4094
5
6
7
TSSOP/SO
V
8
CC
OUT2
7
IN2-
6
IN2+
5
OUT4
14
IN4-
13
IN4+
12
V
11
EE
IN3+
10
IN3-
9
OUT3
8
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= 2.7V to 6V, VEE= GND, VCM= 0, V
OUT
= VCC/2, TA= +25°C.)
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.
Supply Voltage (VCCto VEE)....................................................7V
Common-Mode Input Voltage..........(V
CC
+ 0.3V) to (VEE- 0.3V)
Differential Input Voltage .........................................±(V
CC
- VEE)
Input Current (IN+, IN-) ....................................................±10mA
Output Short-Circuit Duration
OUT shorted to GND or V
CC
.................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)...........571mW
8-Pin SO (derate 5.88mW/°C above +70°C)...............471mW
8-Pin µMAX (derate 4.1mW/°C above +70°C) ............330mW
14-Pin SO (derate 8.33mW/°C above +70°C).............667mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) ........727mW
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
Supply Voltage Range V
Supply Current I
Input Offset Voltage V
Input Bias Current I
Input Offset Current I
CC
CC
OS
B
OS
Inp ut C om m on- M od e Rang eVCMInferred from CMRR test VEE - 0.05 VCC + 0.05 V
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
Large-Signal Voltage Gain (Note 1)
Output Voltage Swing High (Note 1)
Output Voltage Swing Low (Note 1)
CMRR (V
PSRR 2.7V ≤ V
A
VOL
V
OH
V
OL
AC CHARACTERISTICS
Gain-Bandwidth Product GBWP RL = 100k, CL = 100pF 500 kHz Phase Margin φ
M
Gain Margin RL = 100k, CL = 100pF 10 dB
Slew Rate SR RL = 100k, CL = 15pF 0.20 V/µs
Inferred from PSRR test 2.7 6.0 V
VCM = VCC/2
VCM = VEE to V
VCM = VEE to V
VCM = VEE to V
- 0.05V) VCM (V
EE
CC
VCC = 2.7V, R
0.25V V
VCC = 2.7V, R
0.5V ≤ V
OUT
VCC = 5.0V, R
0.25V V
VCC = 5.0V, R
0.5V ≤ V
|V
|V
CC
OUT
- V
- V
OUT
OUT
VCC = 2.7V 115 165
V
CC
CC
CC
CC
6V 86 100 dB
= 100k
L
2.45V
OUT
= 1k
L
2.2V
= 100k
L
4.75V
OUT
= 1k
L
4.5V
|
|
EE
RL = 100k, CL = 100pF 60 d eg r ees
= 5V 130 185
0.03 1.4 mV
20 180 nA
0.2 7 nA
+ 0.05V) 71 90 dB
CC
Sourcing 83 105
Sinking 81 105
Sourcing 91 105
Sinking 78 90
Sourcing 87 115
Sinking 83 115
Sourcing 97 110
Sinking 84 100
RL = 100k 15 69
RL = 1k 130 210
RL = 100k 15 70
RL = 1k 80 220
µA
dB
mV
mV
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 2.7V to 6V, VEE= GND, VCM= 0, V
OUT
= VCC/2, TA= +25°C.)
ELECTRICAL CHARACTERISTICS
(VCC= 2.7V to 6V, VEE= GND, VCM= 0, V
OUT
= VCC/2, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values specified at
T
A
= +25°C.) (Note 2)
Note 1: RLis connected to VEEfor A
VOL
sourcing and VOHtests. RLis connected to VCCfor A
VOL
sinking and VOLtests.
Note 2: All specifications are 100% tested at T
A
= +25°C. Specification limits over temperature (TA= T
MIN
to T
MAX
) are guaranteed
by design, not production tested.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input-Noise Voltage Density e
N
Input-Noise Current Density f = 10kHz 1.5 pA/√Hz
Noise Voltage (0.1Hz to 10Hz)
Total Harmonic Distortion Plus Noise
Capacitive-Load Stability C
Settling Time t
Power-On Time t
THD + N
LOAD
S
ON
Op-Amp Isolation f = 1kHz (MAX4092/MAX4094) 125 dB
f = 10kHz 12 nV/√Hz
16 µV
f = 1kHz, RL = 10k, CL = 15pF, A
V
= 1, V
OUT
= 2V
P-P
0.003 %
AV = 1 2000 pF
To 0.1%, 2V step 12 µs
VCC = 0 to 3V step, VIN = VCC/2,
= 1
A
V
s
RMS
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
Supply Voltage Range V
Supply Current I
Input Offset Voltage V
CC
CC
OS
Input Offset Voltage Tempco ∆VOS/T ±2 µV/°C
Input Bias Current I
Input Offset Current I
Input Common-Mode Range V
B
OS
CM
Common-Mode Rejection Ratio CMRR (VEE - 0.05V) VCM (V Power-Supply Rejection Ratio PSRR 2.7V ≤ V
Large-Signal Voltage Gain (Note 1)
Output Voltage Swing High (Note 1)
Output Voltage Swing Low (Note 1)
A
V
V
VOL
OH
OL
Inferred from PSRR test 2.7 6.0 V
VCM = VCC/2
VCM = VEE to V
VCM = VEE to V
VCM = VEE to V
CC
CC
CC
Inferred from CMRR test V
6V 80 dB
CC
VCC = 2.7V, R
0.25V V
VCC = 2.7V, R
0.5V ≤ V
VCC = 5V, R
0.25V V
VCC = 5V, R
0.5V ≤ V
V
- V
CC
V
- V
OUT
OUT
OUT
OUT
EE
OUT
OUT
= 100k
L
2.45V
= 1k
L
2.2V
= 100k
L
4.75V = 1k
L
4.5V
VCC = 2.7V 200
V
= 5V 225
CC
±3.5 mV
±200 nA
±20 nA
- 0.05 V
E E
+ 0.05V) 62 dB
CC
+ 0.05 V
C C
Sourcing 82
Sinking 80
Sourcing 90
Sinking 76
Sourcing 86
Sinking 82
Sourcing 94
Sinking 80
RL = 100k 75
RL = 1k 250
RL = 100k 75
RL = 1k 250
µA
dB
mV
mV
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
GAIN AND PHASE
80
vs. FREQUENCY
60
40
20
GAIN (dB)
0
-20
-40
0.01 10 10,000
PHASE
0.1 1 100 1000
GAIN
FREQUENCY (kHz)
MAX4091 toc01
AV = 1000 NO LOAD
180
120
60
0
PHASE (DEGREES)
-60
-120
-180
80
60
40
20
GAIN (dB)
0
-20
-40
0.01 10 10,000
CHANNEL ISOLATION
140
120
100
80
60
40
CHANNEL SEPARATION (dB)
20
0
0.01 10 10,000
vs. FREQUENCY
VIN = 2.5V
0.1 1 100 1000 FREQUENCY (kHz)
MAX4901 toc04
160
140
120
V)
m
100
80
60
OFFSET VOLTAGE (
40
20
0
-60 -20 60 140
GAIN AND PHASE
vs. FREQUENCY
CL = 470pF A
V
R
GAIN
PHASE
0.1 1 100 1000 FREQUENCY (kHz)
L
OFFSET VOLTAGE
vs. TEMPERATURE
-40 0 40 80 120
20 100
TEMPERATURE (°C)
MAX4091 toc02
= 1000 =
VCM = 0
180
120
60
0
PHASE (DEGREES)
-60
-120
-180
MAX4091 toc05
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
140
120
100
80
60
PSRR (dB)
40
20
0
-20
0.01 10 1000
V
CC
V
EE
0.1 1 100 FREQUENCY (kHz)
OFFSET VOLTAGE vs.
COMMON-MODE VOLTAGE
100
80
60
40
VCC = 2.7V
20
0
-20
OFFSET VOLTAGE (µV)
-40
-60
-80
-100
-1 7 COMMON-MODE VOLTAGE (V)
VIN = 2.5V
MAX4091 toc03
MAX4091 toc06
VCC = 6V
653 41 20
COMMON-MODE REJECTION RATIO
vs. TEMPERATURE
110
VCM = 0 TO 5V
100
V
= -0.1V TO +5.1V
CM
90
80
CMRR (dB)
70
VCM = -0.2V TO +5.2V
= -0.3V TO +5.3V
V
CM
60
V
= -0.4V TO +5.4V
CM
50
-60 -20 60 140
-40 0 40 80 120
20 100
TEMPERATURE (°C)
MAX4091 toc07
-10
INPUT BIAS CURRENT (nA)
-15
-20
-25
INPUT BIAS CURRENT vs. COMMON-MODE VOLTAGE
25
20
15
10
5
0
-5
06
VCC = 6V
VCC = 2.7V
COMMON-MODE VOLTAGE (V)
MAX4091 toc08
54321
40
30
20
10
-10
INPUT BIAS CURRENT (nA)
-20
-30
-40
INPUT BIAS CURRENT vs.
VCM = V
CC
0
VCM = 0
-50 125
TEMPERATURE
VCC = 6V
VCC = 2.7V
VCC = 6V
TEMPERATURE (°C)
MAX4091 toc09
10075-25 0 25 50
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT PER AMPLIFIER
vs. TEMPERATURE
MAX4091 toc10
TEMPERATURE (°C)
SUPPLY CURRENT PER AMP (µA)
1007525 500-25
20
40
60
80
100
120
140
160
180
200
220
0
-50 125
V
OUT
= VCM = VCC/2
VCC = 5V
VCC = 2.7V
SUPPLY CURRENT PER AMPLIFIER
vs. SUPPLY VOLTAGE
MAX4091 toc11
SUPPLY VOLTAGE (V)
SUPPLY CURRENT PER AMP (µA)
542 3
60
80
100
120
140
160
180
200
40
16
120
GAIN (dB)
110
MAX4091 toc12
70
200
90
VCC - V
OUT
(mV)
500
100
80
60
50
0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1k
W
RL = 10k
W
RL = 100k
W
RL = 1M
W
VCC = 6V R
L
TO V
EE
120
GAIN (dB)
110
MAX4091 toc13
70
200
90
VCC - V
OUT
(mV)
500
100
80
60
50
0 100 300 400 600
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
RL = 1k
W
RL = 10k
W
RL = 100k
W
RL = 1M
W
VCC = 2.7V R
L
TO V
EE
120
80
-60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX4091 toc14
TEMPERATURE (°C)
LARGE-SIGNAL GAIN (dB)
20 100
100
-40 0 40 80 120
85
95
105
115
RL TO V
CC
RL TO V
EE
RL = 1kW, 0.5V < V
OUT
< (VCC - 0.5V)
VCC = 2.7V
VCC = 6V
120
GAIN (dB)
110
MAX4091 toc15
60
100
80
V
OUT
(mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0 200 300 400 600
RL = 1M
W
RL = 100k
W
RL = 10k
W
RL = 1k
W
VCC = 6V R
L
TO V
CC
120
GAIN (dB)
110
MAX4091 toc16
60
100
80
V
OUT
(mV)
500
LARGE-SIGNAL GAIN
vs. OUTPUT VOLTAGE
100
90
70
50
0 200 300 400 600
RL = 1M
W
R
L
= 100k
W
RL = 10k
W
RL = 1k
W
VCC = 2.7V R
L
TO V
CC
120
80
-60 -20 60 140
LARGE-SIGNAL GAIN
vs. TEMPERATURE
90
110
MAX4091 toc17
TEMPERATURE (°C)
LARGE-SIGNAL GAIN (dB)
20 100
100
-40 0 40 80 120
85
95
105
115
RL TO V
CC
RL TO V
EE
RL = 100kW, 0.3V < V
OUT
< (VCC - 0.3V)
VCC = 2.7V
VCC = 6V
100
0
-60 140
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
20
80
MAX4091 toc18
TEMPERATURE (°C)
080
60
40
120
140
160
180
200
220
-40 -20 20 40 60 100 120
RL TO V
CC
VCC = 6V, RL = 1k
W
VCC = 2.7V, RL = 1k
W
VCC = 6V, RL = 100k
W
VCC = 2.7V, RL = 100k
W
MINIMUM V
OUT
(nV)
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
MAXIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
200
RL TO V
180
160
140
120
) (mV)
OUT
100
- V 80
CC
(V
60
40
20
0
-60 140
EE
VCC = 6V, RL = 1k
VCC = 2.7V, RL = 100k
-40 -20 20 40 60 100 120
W
VCC = 2.7V, RL = 1k
VCC = 6V, RL = 100k
W
080
TEMPERATURE (°C)
1000
MAX4091 toc19
)
W
100
W
10
W
OUTPUT IMPEDANCE (
1
0.1
0.01 10 10,000
OUTPUT IMPEDANCE
vs. FREQUENCY
VCM = V
= 2.5V
OUT
0.1 1 100 1,000 FREQUENCY (kHz)
100
Hz)
Ö
MAX40912 toc20
10
VOLTAGE-NOISE DENSITY (nV/
INPUT REFERRED
1
0.01 1
VOLTAGE-NOISE DENSITY
vs. FREQUENCY
0.1 10 FREQUENCY (kHz)
MAX4091 toc21
CURRENT-NOISE DENSITY
vs. FREQUENCY
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0 INPUT REFERRED
CURRENT-NOISE DENSITY (pA/Hz)
0.5
0
0.01 1
0.1 10
FREQUENCY (kHz)
SMALL-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = 1, RL = 10k
V
IN
50mV/div
V
OUT
50mV/div
MAX4091 toc22
MAX4091 toc25
TOTAL HARMONIC DISTORTION PLUS
0.1
0.01
THD + N (%)
0.001
NOISE vs. FREQUENCY
AV = 1
SIGNAL
2V
P-P
80kHz LOWPASS FILTER
RL = 10kW TO GND
10 1000
100 10,000
FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = -1, RL = 10k
V
IN
50mV/div
V
OUT
50mV/div
NO LOAD
MAX4091 toc26
MAX4091 toc23
THD + N (%)
0.001
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. PEAK-TO-PEAK SIGNAL AMPLITUDE
0.1 AV = 1
1kHz SINE 22kHz FILTER
TO GND
R
L
0.01
4.0 4.2 4.7 PEAK-TO-PEAK SIGNAL AMPLITUDE (V)
RL = 1k
W
RL = 2k
W
RL = 100k
RL = 10k
4.3 5.04.1 4.4 4.5 4.6 4.8 4.9
LARGE-SIGNAL TRANSIENT RESPONSE
VCC = 5V, AV = 1, RL = 10k
V
IN
2V/div
V
OUT
2V/div
MAX4091 toc24
W
W
MAX4091 toc27
2µs/div
2µs/div
20µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(VCC= 5V, VEE= 0, TA= +25°C, unless otherwise noted.)
Pin Description
V
IN
2V/div
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4091 toc28
20µs/div
V
OUT
2V/div
VCC = 5V, AV = -1, RL = 10k
SINK CURRENT vs.
OUTPUT VOLTAGE
MAX4091 toc29
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
2.52.01.51.00.5
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
-20 0 3.0
VCC = 2.7V
VCC = 6V
V
DIFF
= 100mV
SOURCE CURRENT vs.
SUPPLY VOLTAGE
MAX4091 toc30
SUPPLY VOLTAGE (V)
OUTPUT CURRENT (mA)
5.04.03.02.0
5
10
15
20
25
30
0
1.0 6.0
V
DIFF
= 100mV
VCC = 2.7V
VCC = 6V
MAX4091 MAX4091
SOT23 SO/µMAX
16—— OUT Amplifier Output
24411 VEENegative Supply
33—— IN+ Noninverting Input
42—— IN- Inverting Input
5784 VCCPositive Supply
1, 5, 8 —— N.C. No Connection. Not internally connected.
—— 1 1 OUT1 Amplifier 1 Output
—— 2 2 IN1- Amplifier 1 Inverting Input
—— 3 3 IN1+ Amplifier 1 Noninverting Input
—— 5 5 IN2+ Amplifier 2 Noninverting Input
—— 6 6 IN2- Amplifier 2 Inverting Input
—— 7 7 OUT2 Amplifier 2 Output
——— 8 OUT3 Amplifier 3 Output
——— 9 IN3- Amplifier 3 Inverting Input
———10 IN3+ Amplifier 3 Noninverting Input
———12 IN4+ Amplifier 4 Noninverting Input
———13 IN4- Amplifier 4 Inverting Input
———14 OUT4 Amplifier 4 Output
PIN
MAX4092 MAX4094
NAME FUNCTION
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
8 _______________________________________________________________________________________
Detailed Description
The single MAX4091, dual MAX4092 and quad MAX4094 op amps combine excellent DC accuracy with rail-to-rail operation at both input and output. With their precision performance, wide dynamic range at low supply voltages, and very low supply current, these op amps are ideal for battery-operated equipment, indus­trial, and data acquisition and control applications.
Applications Information
Rail-to-Rail Inputs and Outputs
The MAX4091/MAX4092/MAX4094s input common­mode range extends 50mV beyond the positive and negative supply rails, with excellent common-mode rejection. Beyond the specified common-mode range, the outputs are guaranteed not to undergo phase reversal or latchup. Therefore, the MAX4091/MAX4092/ MAX4094 can be used in applications with common­mode signals, at or even beyond the supplies, without the problems associated with typical op amps.
The MAX4091/MAX4092/MAX4094s output voltage swings to within 15mV of the supplies with a 100k load. This rail-to-rail swing at the input and the output substantially increases the dynamic range, especially in low-supply-voltage applications. Figure 1 shows the input and output waveforms for the MAX4092, config­ured as a unity-gain noninverting buffer operating from a single 3V supply. The input signal is 3.0V
P-P
, a 1kHz sinusoid centered at 1.5V. The output amplitude is approximately 2.98V
P-P
.
Input Offset Voltage
Rail-to-rail common-mode swing at the input is obtained by two complementary input stages in parallel, which feed a folded cascaded stage. The PNP stage is active for input voltages close to the negative rail, and the NPN stage is active for input voltages close to the positive rail.
The offsets of the two pairs are trimmed. However, there is some residual mismatch between them. This mismatch results in a two-level input offset characteris­tic, with a transition region between the levels occurring at a common-mode voltage of approximately 1.3V above VEE. Unlike other rail-to-rail op amps, the transi­tion region has been widened to approximately 600mV in order to minimize the slight degradation in CMRR caused by this mismatch.
The input bias currents of the MAX4091/MAX4092/ MAX4094 are typically less than 20nA. The bias current flows into the device when the NPN input stage is active, and it flows out when the PNP input stage is active. To reduce the offset error caused by input bias current flowing through external source resistances,
match the effective resistance seen at each input. Connect resistor R3 between the noninverting input and ground when using the op amp in an inverting configu­ration (Figure 2a); connect resistor R3 between the noninverting input and the input signal when using the op amp in a noninverting configuration (Figure 2b). Select R3 to equal the parallel combination of R1 and R2. High source resistances will degrade noise perfor­mance, due to the the input current noise (which is mul­tiplied by the source resistance).
Input Stage Protection Circuitry
The MAX4091/MAX4092/MAX4094 include internal pro­tection circuitry that prevents damage to the precision input stage from large differential input voltages. This protection circuitry consists of back-to-back diodes between IN+ and IN- with two 1.7kresistors in series (Figure 3). The diodes limit the differential voltage applied to the amplifiers internal circuitry to no more than VF, where VFis the diodes forward-voltage drop (about 0.7V at +25°C).
Input bias current for the ICs (±20nA) is specified for small differential input voltages. For large differential input voltages (exceeding VF), this protection circuitry increases the input current at IN+ and IN-:
Output Loading and Stability
Even with their low quiescent current of less than 130µA per op amp, the MAX4091/MAX4092/MAX4094 are well suited for driving loads up to 1kwhile main­taining DC accuracy. Stability while driving heavy capacitive loads is another key advantage over compa­rable CMOS rail-to-rail op amps.
In op amp circuits, driving large capacitive loads increases the likelihood of oscillation. This is especially true for circuits with high-loop gains, such as a unity­gain voltage follower. The output impedance and a capacitive load form an RC network that adds a pole to the loop response and induces phase lag. If the pole frequency is low enoughas when driving a large capacitive load––the circuit phase margin is degraded, leading to either an under-damped pulse response or oscillation.
The MAX4091/MAX4092/MAX4094 can drive capacitive loads in excess of 2000pF under certain conditions (Figure 4). When driving capacitive loads, the greatest potential for instability occurs when the op amp is sourcing approximately 200µA. Even in this case, sta­bility is maintained with up to 400pF of output capaci-
INPUT CURRENT
VVV
[( ) ( )]
=
−−
IN IN F
+−
k
.217
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
_______________________________________________________________________________________ 9
tance. If the output sources either more or less current, stability is increased. These devices perform well with a 1000pF pure capacitive load (Figure 5). Figures 6a, 6b, and 6c show the performance with a 500pF load in par­allel with various load resistors.
To increase stability while driving large-capacitive loads, connect a pullup resistor to VCCat the output to decrease the current the amplifier must source. If the amplifier is made to sink current rather than source, stability is further increased.
Frequency stability can be improved by adding an out­put isolation resistor (RS) to the voltage-follower circuit (Figure 7). This resistor improves the phase margin of the circuit by isolating the load capacitor from the op amps output. Figure 8a shows the MAX4092 driving 5000pF (RL≥ 100kΩ), while Figure 8b adds a 47Ω iso­lation resistor.
Because the MAX4091/MAX4092/MAX4094 have excel­lent stability, no isolation resistor is required, except in the most demanding applications. This is beneficial because an isolation resistor would degrade the low­frequency performance of the circuit.
Power-Up Settling Time
The MAX4091/MAX4092/MAX4094 have a typical sup­ply current of 130µA per op amp. Although supply cur­rent is already low, it is sometimes desirable to reduce it further by powering down the op amp and associated ICs for periods of time. For example, when using a MAX4092 to buffer the inputs of a multi-channel analog­to-digital converter (ADC), much of the circuitry could be powered down between data samples to increase battery life. If samples are taken infrequently, the op amps, along with the ADC, may be powered down most of the time.
When power is reapplied to the MAX4091/MAX4092/
MAX4094, it takes some time for the voltages on the supply pin and the output pin of the op amp to settle. Supply settling time depends on the supply voltage, the value of the bypass capacitor, the output impedance of the incoming supply, and any lead resistance or induc­tance between components. Op amp settling time depends primarily on the output voltage and is slew­rate limited. With the noninverting input to a voltage fol­lower held at midsupply (Figure 9), when the supply steps from 0 to V
CC
, the output settles in approximately 2µs for VCC= 3V (Figure 10a) and 8µs for VCC= 5V (Figure 10b).
Power Supplies and Layout
The MAX4091/MAX4092/MAX4094 operate from a sin­gle 2.7V to 6V power supply, or from dual supplies of ±1.35V to ±3V. For single-supply operation, bypass the power supply with a 0.1µF capacitor. If operating from dual supplies, bypass each supply to ground.
Good layout improves performance by decreasing the amount of stray capacitance at the op amps inputs and output. To decrease stray capacitance, minimize both trace lengths and resistor leads and place exter­nal components close to the op amps pins.
Chip Information
MAX4091 TRANSISTOR COUNT: 168
MAX4092 TRANSISTOR COUNT: 336
MAX4094 TRANSISTOR COUNT: 670
PROCESS: Bipolar
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
10 ______________________________________________________________________________________
Test Circuits/Timing Diagrams
Figure 1. Rail-to-Rail Input and Output Operation
Figure 2a. Reducing Offset Error Due to Bias Current: Inverting Configuration
Figure 2b. Reducing Offset Error Due to Bias Current: Noninverting Configuration
Figure 3. Input Stage Protection Circuitry
V
= 3V
V
1V/div
V
OUT
1V/div
CC
= 0
V
EE
IN
200µs/div
R1
V
IN
R3
R2
MAX409_
R3 = R2 II R1
V
OUT
R3
V
IN
V
MAX409_
R3 = R2 II R1
OUT
R2
R1
IN+
IN–
1.7k
1.7k
TO INTERNAL CIRCUITRY
TO INTERNAL CIRCUITRY
MAX4091 MAX4092 MAX4094
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 11
Test Circuits/Timing Diagrams (continued)
Figure 4. Capacitive-Load Stable Region Sourcing Current
Figure 5. MAX4092 Voltage Follower with 1000pF Load
Figure 6a. MAX4092 Voltage Follower with 500pF Load (R
L
= 5kΩ)
Figure 6b. MAX4092 Voltage Follower with 500pF Load (R
L
= 20kΩ)
10,000
UNSTABLE REGION
1000
CAPACITIVE LOAD (pF)
100
RESISTIVE LOAD (k)
VCC = 5V
= VCC/2
V
OUT
TO V
R
L
EE
AV = 1
10
1001
RL =
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
RL = 5k
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
RL = 20k
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
12 ______________________________________________________________________________________
Figure 6c. MAX4092 Voltage Follower with 500pF Load (R
L
= ∞)
Figure 7. Capacitive-Load Driving Circuit
Test Circuits/Timing Diagrams (continued)
Figure 8a. Driving a 5000pF Capacitive Load
Figure 8b. Driving a 5000pF Capacitive Load with a 47 Isolation Resistor
RL =
V
IN
50mV/div
R
V
OUT
50mV/div
10µs/div
S
MAX409_
V
IN
V
OUT
C
L
V
IN
50mV/div
V
OUT
50mV/div
10µs/div
50mV/div
V
OUT
50mV/div
V
IN
10µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 13
Test Circuits/Timing Diagrams (continued)
Figure 9. Power-Up Test Configuration
Figure 10a. Power-Up Settling Time (VCC= +3V)
Figure 10b. Power-Up Settling Time (VCC= +5V)
5V
1k
1k
2
3
MAX409_
V
CC
7
6
V
OUT
4
1V/div
V
OUT
500mV/div
V
IN
5µs/div
V
IN
2V/div
V
OUT
1V/div
5µs/div
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
14 ______________________________________________________________________________________
Package Information
SOT5L.EPS
8LUMAXD.EPS
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply,
Rail-to-Rail Op Amps
______________________________________________________________________________________ 15
Package Information (continued)
SOICN.EPS
MAX4091/MAX4092/MAX4094
Single/Dual/Quad, Micropower, Single-Supply, Rail-to-Rail Op Amps
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Package Information (continued)
TSSOP,NO PADS.EPS
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