19-1343; Rev 3; 9/06
Single/Dual/Quad, +1.8V/10µA, SOT23,
Beyond-the-Rails Op Amps
MAX4240–MAX4244
General Description Features
The MAX4240–MAX4244 family of micropower op amps operate from a single +1.8V to +5.5V supply or dual
±0.9V to ±2.75V supplies and have Beyond-the-Rails™ inputs and rail-to-rail output capabilities. These ampli- fiers provide a 90kHz gain-bandwidth product while using only 10µA of supply current per amplifier. The MAX4241/MAX4243 have a low-power shutdown mode that reduces supply current to less than 1µA and forces the output into a high-impedance state. Although the minimum operating voltage is specified at +1.8V, these devices typically operate down to +1.5V. The combina- tion of ultra-low-voltage operation, beyond-the-rails inputs, rail-to-rail outputs, and ultra-low power con- sumption makes these devices ideal for any portable/ two-cell battery-powered system.
These amplifiers have an input common-mode range that extends 200mV beyond each rail, and their out- puts typically swing to within 9mV of the rails with a 100k load. Beyond-the-rails input and rail-to-rail out- put characteristics allow the full power-supply voltage to be used for signal range. The combination of low input offset voltage, low input bias current, and high open-loop gain makes them suitable for low-power/low- voltage precision applications.
The MAX4240 is offered in a space-saving 5-pin SOT23 package. All specifications are guaranteed over the -40°C to +85°C extended temperature range.
Applications
♦ Ultra-Low-Voltage Operation: Guaranteed Down to +1.8V Typical Operation to +1.5V
♦ Ultra-Low Power Consumption: 10µA Supply Current per Amplifier
1µA Shutdown Mode (MAX4241/MAX4243) Up to 200,000 Hours Operation from Two AA Alkaline Cells
♦ Beyond-the-Rails Input Common-Mode Range
♦ Outputs Swing Rail-to-Rail
♦ No Phase Reversal for Overdriven Inputs
♦ 200µV Input Offset Voltage
♦ Unity-Gain Stable for Capacitive Loads up to 200pF
♦ 90kHz Gain-Bandwidth Product
♦ Available in Space-Saving 5-Pin SOT23 and 8-Pin µMAX® Packages
PART | TEMP RANGE | PIN- PACKAGE | TOP MARK |
MAX4240EUK-T | -40°C to +85°C | 5 SOT23-5 | ACCS |
MAX4241EUA | -40°C to +85°C | 8 µMAX | — |
MAX4241ESA | -40°C to +85°C | 8 SO | — |
MAX4242EUA | -40°C to +85°C | 8 µMAX | — |
MAX4242ESA | -40°C to +85°C | 8 SO | — |
MAX4243EUB | -40°C to +85°C | 10 µMAX | — |
MAX4243ESD | -40°C to +85°C | 14 SO | — |
MAX4244ESD | -40°C to +85°C | 14 SO | — |
Ordering Information
Two-Cell Battery- Powered Systems
Portable/Battery-Powered Electronic Equipment
Digital Scales
Strain Gauges Sensor Amplifiers Cellular Phones Notebook Computers PDAs
Selector Guide
PART | NO. OF AMPS | SHUTDOWN | PIN-PACKAGE |
MAX4240 | 1 | — | 5-pin SOT23 |
MAX4241 | 1 | Yes | 8-pin µMAX/SO |
MAX4242 | 2 | — | 8-pin µMAX/SO |
MAX4243 | 2 | Yes | 10-pin µMAX, 14-pin SO |
MAX4244 | 4 | — | 14-pin SO |
Beyond-the-Rails is a trademark and µMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations
TOP VIEW
OUT 1
5 VCC
VEE
2
MAX4240
IN+ 3
4 IN-
SOT23-5
Pin Configurations continued at end of data sheet.
Maxim Integrated Products 1
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE) ....................................................6V 10-pin µMAX (derate 5.6mW/°C above +70°C) ............444mW
All Other Pins ...................................(VCC + 0.3V) to (VEE - 0.3V) 14-pin SO (derate 8.33mW/°C above +70°C)...............667mW
Output Short-Circuit Duration (to VCC or VEE)............Continuous Operating Temperature Range ...........................-40°C to +85°C
Continuous Power Dissipation (TA = +70°C) Junction Temperature ......................................................+150°C
5-pin SOT23 (derate 7.1mW/°C above +70°C).............571mW Storage Temperature Range .............................-65°C to +160°C
8-pin µMAX (derate 4.1mW/°C above +70°C) ..............330mW Lead Temperature (soldering, 10s) .................................+300°C 8-pin SO (derate 5.88mW/°C above +70°C).................471mW
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
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN | TYP | MAX | UNITS | |
Supply-Voltage Range | VCC | Inferred from PSRR test | 1.8 | 5.5 | V | ||
Supply Current per Amplifier | ICC | SHDN = VCC | VCC = 1.8V | 10 12 | µA | ||
VCC = 5.0V | 14 18 | ||||||
Shutdown Supply Current (Note 2) | ICC(SHDN) | SHDN = VEE | VCC = 1.8V | 1.0 1.5 | µA | ||
VCC = 5.0V | 2.0 3.0 | ||||||
Input Offset Voltage | VOS | (VEE - 0.2V) VCM (VCC + 0.2V) | MAX4241ESA | ±0.20 ±0.75 | mV | ||
MAX4242ESA/MAX4243ESD/ MAX4244ESD | ±0.20 ±0.88 | ||||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | ±0.25 ±1.40 | ||||||
Input Bias Current | IB | (Note 3) | ±2 ±6 | nA | |||
Input Offset Current | IOS | (Note 3) | ±0.5 ±1.5 | nA | |||
Differential Input Resistance | RIN(DIFF) | ⎥VIN+ - VIN-⎥ < 1.0V | 45 | MΩ | |||
⎥VIN+ - VIN-⎥ > 2.5V | 4.4 | kΩ | |||||
Input Common-Mode Voltage Range | VCM | Inferred from the CMRR test | VEE - 0.2 | VCC + 0.2 | V | ||
Common-Mode Rejection Ratio (Note 4) | CMRR | VCC = 1.8V | MAX4241ESA | 72 | 90 | dB | |
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 69 | 90 | |||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 63 | 88 | |||||
VCC = 5.0V | MAX4241ESA | 74 | 94 | ||||
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 74 | 94 | |||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 69 | 90 |
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN | TYP | MAX | UNITS | ||
Power-Supply Rejection Ratio | PSRR | 1.8V VCC 5.5V | MAX4241ESA | 77 | 85 | dB | ||
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 77 | 85 | ||||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 75 | 82 | ||||||
Large-Signal Voltage Gain | AVOL | (VEE + 0.2V) VOUT (VCC - 0.2V) | VCC = 1.8V | RL = 100kΩ | 76 | 85 | dB | |
RL = 10kΩ | 66 | 73 | ||||||
VCC = 5.0V | RL = 100kΩ | 86 | 94 | |||||
RL = 10kΩ | 78 | 85 | ||||||
Output Voltage Swing High | VOH | Specified as ⎥VCC - VOH⎥ | VCC = 1.8V | RL = 100kΩ | 8 | 20 | mV | |
RL = 10kΩ | 40 | 65 | ||||||
VCC = 5.0V | RL = 100kΩ | 10 | 25 | |||||
RL = 10kΩ | 60 | 95 | ||||||
Output Voltage Swing Low | VOL | Specified as ⎥VEE - VOL⎥ | VCC = 1.8V | RL = 100kΩ | 6 | 15 | mV | |
RL = 10kΩ | 23 | 35 | ||||||
VCC = 5.0V | RL = 100kΩ | 10 | 20 | |||||
RL = 10kΩ | 40 | 60 | ||||||
Output Short-Circuit Current | IOUT(SC) | Sourcing | 0.7 | mA | ||||
Sinking | 2.5 | |||||||
Output Leakage Current in Shutdown (Notes 2, 5) | IOUT(SHDN) | SHDN = VEE = 0, VCC = 5.5V | 20 | 50 | nA | |||
SHDN Logic Low (Note 2) | VIL | 0.3 x VCC | V | |||||
SHDN Logic High (Note 2) | VIH | 0.7 x VCC | V | |||||
SHDN Input Bias Current (Note 2) | IIH, IIL | SHDN = VCC = 5.5V or SHDN = VEE = 0 | 40 | 80 | nA | |||
Channel-to-Channel Isolation (Note 6) | CHISO | Specified at DC | 80 | dB | ||||
Gain-Bandwidth Product | GBW | 90 | kHz | |||||
Phase Margin | m | 68 | degrees | |||||
Gain Margin | Gm | 18 | dB | |||||
Slew Rate | SR | 40 | V/ms |
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN TYP MAX | UNITS |
Input Voltage-Noise Density | en | f = 1kHz | 70 | nV/Hz |
Input Current-Noise Density | in | f = 1kHz | 0.05 | pA/Hz |
Capacitive-Load Stability | AVCL = +1V/V, no sustained oscillations | 200 | pF | |
Shutdown Time | tSHDN | 50 | µs | |
Enable Time from Shutdown | tENABLE | 150 | µs | |
Power-Up Time | tON | 200 | µs | |
Input Capacitance | CIN | 3 | pF | |
Total Harmonic Distortion | THD | fIN = 1kHz, VCC = 5.0V, VOUT = 2Vp-p, AV = +1V/V | 0.05 | % |
Settling Time to 0.01% | tS | AV = +1V/V, VCC = 5.0V, VOUT = 2VSTEP | 50 | µs |
ELECTRICAL CHARACTERISTICS
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = TMIN to TMAX, unless oth-
erwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN TYP MAX | UNITS | |
Supply-Voltage Range | VCC | Inferred from PSRR test | 1.8 5.5 | V | |
Supply Current per Amplifier | ICC | SHDN = VCC | VCC = 1.8V | 14 | µA |
VCC = 5.0V | 19 | ||||
Shutdown Supply Current (Note 2) | ICC(SHDN) | SHDN = VEE | VCC = 1.8V | 2.0 | µA |
VCC = 5.0V | 3.5 | ||||
Input Offset Voltage | VOS | (VEE - 0.2V) VCM (VCC + 0.2V) | MAX4241ESA | ±1.2 | mV |
MAX4242ESA/MAX4243ESD/ MAX4244ESD | ±1.3 | ||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | ±2.0 | ||||
Input Offset Voltage Drift | TCVOS | 2 | µV/°C | ||
Input Bias Current | IB | (Note 3) | ±15 | nA | |
Input Offset Current | IOS | (Note 3) | ±7 | nA | |
Input Common-Mode Voltage Range | VCM | Inferred from the CMRR test | -0.2 VCC + 0.2 | V |
ELECTRICAL CHARACTERISTICS
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = TMIN to TMAX, unless oth-
erwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN TYP MAX | UNITS | ||
Common-Mode Rejection Ratio (Note 4) | CMRR | VCC = 1.8V | MAX4241ESA | 65 | dB | |
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 65 | |||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 61 | |||||
VCC = 5.0V | MAX4241ESA | 71 | ||||
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 71 | |||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 67 | |||||
Power-Supply Rejection Ratio | PSRR | 1.8V VCC 5.5V | MAX4241ESA | 73 | dB | |
MAX4242ESA/MAX4243ESD/ MAX4244ESD | 73 | |||||
MAX4240EUK/MAX424_EUA/ MAX4243EUB | 71 | |||||
Large-Signal Voltage Gain | AVOL | (VEE + 0.2V) VOUT (VCC - 0.2V) | VCC = 1.8V | RL = 100kΩ | 72 | dB |
RL = 10kΩ | 62 | |||||
VCC = 5.0V | RL = 100kΩ | 80 | ||||
RL = 10kΩ | 72 | |||||
Output Voltage Swing High | VOH | Specified as ⎥VCC - VOH⎥ | VCC = 1.8V | RL = 100kΩ | 25 | mV |
RL = 10kΩ | 95 | |||||
VCC = 5.0V | RL = 100kΩ | 30 | ||||
RL = 10kΩ | 145 | |||||
Output Voltage Swing Low | VOL | Specified as ⎥VEE - VOL⎥ | VCC = 1.8V | RL = 100kΩ | 20 | mV |
RL = 10kΩ | 50 | |||||
VCC = 5.0V | RL = 100kΩ | 25 | ||||
RL = 10kΩ | 75 | |||||
Output Leakage Current in Shutdown (Notes 2, 5) | IOUT(SHDN) | SHDN = VEE = 0, VCC = 5.5V | 100 | nA | ||
SHDN Logic Low (Note 2) | VIL | 0.3 x VCC | V |
(VCC = +1.8V to +5.5V, VEE = 0, VCM = 0, VOUT = VCC / 2, RL = 100kΩ tied to VCC / 2, SHDN = VCC, TA = TMIN to TMAX, unless oth-
erwise noted.) (Note 1)
PARAMETER | SYMBOL | CONDITIONS | MIN TYP MAX | UNITS |
SHDN Logic High (Note 2) | VIH | 0.7 x VCC | V | |
SHDN Input Bias Current (Note 2) | IIH, IIL | SHDN = VCC = 5.5V or SHDN = VEE = 0 | 120 | nA |
Note 1: The MAX4240EUK, MAX4241EUA, MAX4242EUA, and MAX4243EUB specifications are 100% tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 2: Shutdown mode applies to the MAX4241/MAX4243 only.
Note 3: Input bias current and input offset current are tested with VCC = +0.5V and +0.5V VCM +4.5V.
Note 4: Tested over the specified input common-mode range.
Note 5: Tested for 0 VOUT VCC. Does not include current through external feedback network.
Note 6: Channel-to-channel isolation specification applies to the MAX4242/MAX4243/MAX4244 only.
Typical Operating Characteristics
(VCC = +5.0V, VEE = 0, VCM = VCC / 2, VSHDN = VCC, RL = 100kΩ to VCC / 2, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT PERAMPLIFIER SHUTDOWNSUPPLY CURRENT MINIMUM OPERATINGVOLTAGE vs. TEMPERATURE PERAMPLIFIER vs. TEMPERATURE vs. TEMPERATURE
MAX4240/44-01
MAX4240/44-02
MAX4240/44-03
20 5 1.8
SHUTDOWNSUPPLYCURRENTA()
18 1.7
PSRR 80dB
SUPPLYCURRENT(A)
16 VCC=+5.5V
14
4
1.6
12 3
10
VCC=+5.5V
1.5
VCC(V)
1.4
8 VCC=+1.8V
6
2
VCC=+1.8V
1.3
1.2
4 1
2 1.1
0 0 1.0
-60 -40 -20 0
20 40
60 80
100
-60 -40 -20 0 20 40
60 80
100
-60 -40 -20 0
20 40
60 80
100
TEMPERATURE(°C) TEMPERATURE(°C) TEMPERATURE(°C)
INPUTOFFSET VOLTAGE INPUT BIASCURRENT INPUT BIASCURRENT vs.
vs. TEMPERATURE vs. TEMPERATURE COMMON-MODE VOLTAGE (VCC= 1.8V)
VCC=+1.8V
VCM =0
MAX4240/44-04
MAX4240/44-05
MAX4240/44-06a
VCC=+1.8V | ||||||||||
400 0 5.0
VCC=+5.5V
INPUTOFFSETVOLTAGE(V)
INPUTBIASCURRENT(nA)
300 -1 2.5
IBIAS(nA)
200 -2 0
100 -3 -2.5
0
-60 -40 -20 0
20 40
60 80
100
-4
-60 -40 -20 0 20 40 60 80 100
-5.0
-0.2 0.2 0.6 1.0 1.4
1.8
TEMPERATURE(°C) TEMPERATURE(°C) VCM (V)
Typical Operating Characteristics (continued)
(VCC = +5.0V, VEE = 0, VCM = VCC / 2, VSHDN = VCC, RL = 100kΩ to VCC / 2, TA = +25°C, unless otherwise noted.)
INPUT BIASCURRENT vs. OUTPUT SWINGHIGH OUTPUT SWINGLOW
COMMON-MODE VOLTAGE (VCC= 5.5V) vs. TEMPERATURE vs. TEMPERATURE
5.0
2.5
IBIAS(nA)
0
VCC=+5.5V
120
MAX4240/44-06b
VOLTAGEFROMVCC(mV)
100
80
60
40
RLTOVEE
VCC=+1.8V,RL=10kΩ
VCC=+5.5V,RL=20kΩ
120
MAX4240/44-07
VOLTAGEFROMVEE(mV)
100
80
60
40
RLTOVCC
MAX4240/44-08
VCC=+5.5V,RL=20kΩ
-2.5
VCC
20
=+5.5V,RL=100kΩ
VCC=+1.8V,RL=10kΩ
20 VCC=+5.5V,RL=100kΩ
-5.0
VCC=+1.8V,RL=100kΩ
0
VCC=+1.8V,RL=100kΩ
0
-0.5 0.5 1.5 2.5
3.5 4.5 5.5 -60 -40 -20 0
20 40
60 80 100 -60 -40 -20 0
20 40
60 80 100
COMMON-MODEREJECTION(dB)
-80
-85
VCM (V)
COMMON-MODEREJECTION vs. TEMPERATURE
TEMPERATURE(°C)
OPEN-LOOPGAIN vs. OUTPUT SWINGLOW (VCC= +1.8V, RLTIED TOVEE)
MAX4240/44-09
MAX4240/44-10
RL=100kΩ | |||||||||
RL=10kΩ | |||||||||
100 100
90 90
80 80
TEMPERATURE(°C)
MAX4240/44-11
OPEN-LOOPGAIN vs. OUTPUT SWINGHIGH (VCC= +1.8V, RLTIED TOVEE)
RL=100kΩ
RL=10kΩ
-90
-95
VCC=+1.8V
VCC=+5.5V
70 70
GAIN(dB)
GAIN(dB)
60 60
50 50
40 40
-100
30 30
-60 -40 -20 0 20 40 60 80 100 0 100 200 300 400 500 0 100 200 300 400 500
TEMPERATURE(°C) ΔVOUT(mV) ΔVOUT(mV)
MAX4240/44-14
OPEN-LOOPGAIN vs. OUTPUT SWINGLOW OPEN-LOOPGAIN vs. OUTPUT SWINGHIGH OPEN-LOOPGAIN (VCC= +5.5V, RLTIED TOVEE) (VCC= +5.5V, RLTIED TOVEE) vs. TEMPERATURE
110
100
90
GAIN(dB)
80
70
60
50
40
RL=100kΩ
RL=20kΩ
110
MAX4240/44-12
100
90
GAIN(dB)
80
70
60
50
40
RL=100kΩ
RL=20kΩ
110
MAX4240/44-13
105
100
GAIN(dB)
95
90
85
80
75
70
VCC=+5.5V,RL=20kΩ TOVEE
VCC=+5.5V,RL=20kΩ TOVCC
VCC=+1.8V,RL=10kΩ TOVEE
VCC=+1.8V,RL=10kΩ TOVCC
0 100 200 300 400
0 100 200 300 400
-60 -40 -20 0 20 40 60 80 100
ΔVOUT(mV) ΔVOUT(mV) TEMPERATURE(°C)
GAIN (dB)
(VCC = +5.0V, VEE = 0, VCM = VCC/2, VSHDN = VCC, RL = 100kΩ to VCC/2, TA = +25°C unless otherwise noted.)
VCC = +5.5V, RL TO VEE
110
OPEN-LOOP GAIN vs. TEMPERATURE
GAIN AND PHASE vs. FREQUENCY (CL = 0pF)
MAX4240/44-15
AV = +1000V/V | |||||||||||||
60 MAX4240/44-16
180
GAIN AND PHASE vs. FREQUENCY (CL = 100pF)
60 MAX4240/44-17
180
105
50 144 50
AV = +1000V/V
144
100
40 108 40
108
95 VCC = +5.5V, RL TO VCC
VCC = +1.8V, RL TO VCC
90 VCC = +1.8V, RL TO VEE 85
80
30 72
GAIN (dB)
20 36
10 0
0 -36
-10 -72
30
PHASE (DEGREES)
GAIN (dB)
20
10
0
-10
72
PHASE (DEGREES)
36
0
-36
-72
-20
-108
-20
-108
75 -30
-144
-30 -144
70
-60 -40 -20 0
20 40
60 80
100
-40 -180
10 100 1k 10k 100k
-40 -180
10 100 1k 10k 100k
-60
THD + NOISE (%)
-70
TEMPERATURE (°C)
MAX4242/MAX4243/MAX4244 CROSSTALK vs. FREQUENCY
VOLTAGE NOISE DENSITY (nVHz)
RL = 10k
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY
MAX4240/44-18
MAX4240/44-19
1
1000
FREQUENCY (Hz)
MAX4240 toc20
VOLTAGE NOISE vs. FREQUENCY
GAIN (dB)
-80
-90
0.1
100
-100
-110
0.01
RL = 100k
RL = 10k
10
1000
RLOAD (k)
100
10
10 100 1k 10k FREQUENCY (Hz)
LOAD RESISTOR vs. CAPACITIVE LOAD
10% OVERSHOOT
REGION OF MARGINAL STABILITY
REGION OF STABLE OPERATION
IN
0mV/div
OUT
1 10 100 1000
FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE (NONINVERTING)
MAX4240/44-22
100mV
0V
100mV
0V
IN
50mV/div
OUT
0.1 1 10
FREQUENCY (Hz)
SMALL-SIGNAL TRANSIENT RESPONSE (INVERTING)
MMAXA4X2424400//4444--2201
MAX4240/44-23
100mV
0V
100mV
0V
0 250 500 750 1000
CLOAD (pF)
10μs/div
10μs/div
8
(VCC = +5.0V, VEE = 0, VCM = VCC/2, VSHDN = VCC, RL = 100kΩ to VCC/2, TA = +25°C unless otherwise noted.)
9
Detailed Description
Beyond-the-Rails Input Stage The MAX4240–MAX4244 have Beyond-the-Rails inputs and rail-to-rail output stages that are specifically designed for low-voltage, single-supply operation. The input stage consists of separate NPN and PNP differen- tial stages, which operate together to provide a com- mon-mode range extending to 200mV beyond both supply rails. The crossover region of these two pairs occurs halfway between VCC and VEE. The input offset voltage is typically 200µV. Low operating supply voltage, low supply current, beyond-the-rails common-mode input range, and rail-to-rail outputs make this family of operational amplifiers an excellent choice for precision or general-purpose, low-voltage battery-powered systems.
Since the input stage consists of NPN and PNP pairs, the input bias current changes polarity as the common- mode voltage passes through the crossover region. Match the effective impedance seen by each input to reduce the offset error caused by input bias currents flowing through external source impedances (Figures 1a and 1b). The combination of high source impedance plus input capacitance (amplifier input capacitance plus stray capacitance) creates a parasitic pole that produces an underdamped signal response. Reducing input capacitance or placing a small capacitor across the feedback resistor improves response in this case.
The MAX4240–MAX4244 family’s inputs are protected from large differential input voltages by internal 2.2kΩ series resistors and back-to-back triple-diode stacks across the inputs (Figure 2). For differential input volt- ages (much less than 1.8V), input resistance is typically 45MΩ. For differential input voltages greater than 1.8V, input resistance is around 4.4kΩ, and the input bias current can be approximated by the following equation:
IBIAS = (VDIFF - 1.8V) / 4.4kΩ
VIN
R3
MAX4240 MAX4241 MAX4242 MAX4243 MAX4244
R3=R1 R2
R1
R2
MAX4240 MAX4241 MAX4242 MAX4243 MAX4244
R3
Figure 1a. Minimizing Offset Error Due to Input Bias Current (Noninverting)
R3=R1 R2
VIN
R1
R2
Figure 1b. Minimizing Offset Error Due to Input Bias Current (Inverting)
IN+
2.2kΩ
IN-
2.2kΩ
Figure 2. Input Protection Circuit
OUT
RL=100kΩ TIEDTOVEE VIN=2.0V
fIN=1kHz
1V/div
MAX4240-44 fig03
In the region where the differential input voltage approaches 1.8V, the input resistance decreases expo- nentially from 45MΩ to 4.4kΩ as the diode block begins conducting. Conversely, the bias current increases with the same curve.
Rail-to-Rail Output Stage The MAX4240–MAX4244 output stage can drive up to a 10kΩ load and still swing to within 40mV of the rails. Figure 3 shows the output voltage swing of a MAX4240 configured as a unity-gain buffer, powered from a single
+2V supply voltage. The output for this setup typically swings from (VEE + 6mV) to (VCC - 8mV) with a 100kΩ load.
Applications Infor mation
Power-Supply Considerations The MAX4240–MAX4244 operate from a single +1.8V to +5.5V supply (or dual ±0.9V to ±2.75V supplies) and consume only 10µA of supply current per amplifier. A high power-supply rejection ratio of 85dB allows the amplifiers to be powered directly off a decaying battery voltage, simplifying design and extending battery life.
The MAX4240–MAX4244 are ideally suited for use with most battery-powered systems. Table 1 lists a variety of typical battery types showing voltage when fresh, volt- age at end-of-life, capacity, and approximate operating time from a MAX4240/MAX4241, assuming nominal conditions for both normal and shutdown modes.
PSRR(dB)
Although the amplifiers are fully guaranteed over tem- perature for operation down to a +1.8V single supply, even lower-voltage operation is possible in practice. Figures 4 and 5 show the PSRR and supply current as
1V/div
IN
200s/div
MAX4240-44 fig04
Figure 3. Rail-to-Rail Input/Output Voltage Range
100
TA=+85°C
90
80
TA= -40°C
70
TA=+25°C
60
1.0 1.2 1.4 1.6 1.8 2.0
SUPPLYVOLTAGE(V)
a function of supply voltage and temperature. Figure 4. Power-Supply Rejection Ratio vs. Supply Voltage
12
10
8
SUPPLYCURRENT(A)
MAX4240-44 fig05
Power-Up Settling Time The MAX4240–MAX4244 typically require 200µs to power up after VCC is stable. During this start-up time, the output is indeterminant. The application circuit should allow for this initial delay.
1.0 1.2 1.4 1.6 1.8 2.0
SUPPLYVOLTAGE(V)
2
0
TA=+25°C
TA= -40°C
6
4
TA=+85°C
Shutdown Mode The MAX4241 (single) and MAX4243 (dual) feature a low-power shutdown mode. When the shutdown pin (SHDN) is pulled low, the supply current drops to 1µA per amplifier, the amplifier is disabled, and the outputs enter a high-impedance state. Pulling SHDN high or leaving it floating enables the amplifier. Take care to ensure that parasitic leakage current at the SHDN pin does not inadvertently place the part into shutdown mode when SHDN is left floating. Figure 6 shows the output voltage response to a shutdown pulse. The logic
threshold for SHDN is always referred to VCC / 2 (not to Figure 5. Supply Current vs. Supply Voltage
MAX4240-44 fig07a
Table 1. MAX4240/MAX4241 Characteristics with Typical Battery Systems
BATTERY TYPE | RECHARGEABLE | VFRESH (V) | VEND-OF-LIFE (V) | CAPACITY, AA SIZE (mA-h) | MAX4240/MAX4241 OPERATING TIME IN NORMAL MODE (Hours) | MAX4241 OPERATING TIME IN SHUTDOWN MODE (Hours) |
Alkaline (2 Cells) | No | 3.0 | 1.8 | 2000 | 200,000 | 2 x 106 |
Nickel- Cadmium (2 Cells) | Yes | 2.4 | 1.8 | 750 | 75,000 | 0.75 x 106 |
Lithium-Ion (1 Cell) | Yes | 3.5 | 2.7 | 1000 | 100,000 | 106 |
Nickel-Metal- Hydride (2 Cells) | Yes | 2.4 | 1.8 | 1000 | 100,000 | 106 |
VIN=2V
RL=100kΩ TIEDTOVEE SHDN
MAX4240-44 fig06
1200
200 VCC= 5.5V,VOH=50mV VCC= 1.8V, VOH= 50mV
0
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE(°C)
VCC=1.8V, VOH=100mV
600
400
VCC=5.5V,VOH=100mV
VCC=1.8V, VOH=200mV
800
1000
VCC=5.5V,VOH=200mV
200s/div
1V/div
OUT
5V/div
OUTPUTSOURCECURRENT(A)
Figure 6. Shutdown Enable/Disable Output Voltage Figure 7a. Output Source Current vs. Temperature
3000
2500
MAX4240-44 fig07b
GND). When using dual supplies, pull SHDN to VEE to enter shutdown mode.
1000
VCC=1.8V,VOL=100mV
500 VCC=5.5V,VOL= 50mV
VCC= 1.8V, VOL=50mV
0
-60 -40 -20 0 20 40 60 80 100
TEMPERATURE(°C)
VCC=5.5V, VOL=100mV
1500
VCC=1.8V,VOL =200mV
2000
VCC= 5.5V,VOL=200mV
OUTPUTSINKCURRENT(A)
Load-Driving Capability The MAX4240–MAX4244 are fully guaranteed over tem- perature and supply voltage to drive a maximum resis- tive load of 10kΩ to VCC / 2, although heavier loads can be driven in many applications. The rail-to-rail output stage of the amplifier can be modeled as a current source when driving the load toward VCC, and as a cur- rent sink when driving the load toward VEE. The magni- tude of this current source/sink varies with supply voltage, ambient temperature, and lot-to-lot variations of the units.
Figures 7a and 7b show the typical current source and sink capability of the MAX4240–MAX4244 family as a function of supply voltage and ambient temperature.
The contours on the graph depict the output current Figure 7b. Output Sink Current vs. Temperature
value, based on driving the output voltage to within and VEE supplies should be bypassed to ground with 50mV, 100mV, and 200mV of either power-supply rail. separate 100nF capacitors.
For example, a MAX4241 running from a single +1.8V Good PC board layout techniques optimize perfor- supply, operating at TA = +25°C, can source 240µA to mance by decreasing the amount of stray capacitance within 100mV of VCC and is capable of driving a 7kΩ at the op amp’s inputs and output. To decrease stray load resistor to VEE: capacitance, minimize trace lengths by placing exter- nal components as close as possible to the op amp.
RL =
1.8V - 0.1V
240A
7kΩ to VEE
Surface-mount components are an excellent choice.
The same application can drive a 3.3kΩ load resistor when terminated in VCC / 2 (+0.9V in this case).
□
CL
RL
MAX4240 MAX4241 MAX4242 MAX4243 MAX4244
RISO
Driving Capacitive Loads The MAX4240–MAX4244 are unity-gain stable for loads up to 200pF (see Load Resistor vs. Capacitive Load graph in Typical Operating Characteristics). Applica- tions that require greater capacitive drive capability should use an isolation resistor between the output and the capacitive load (Figure 8). Note that this alternative results in a loss of gain accuracy because RISO forms a voltage divider with the load resistor.
RL+RISO
AV= RL 1
Power-Supply Bypassing and Layout The MAX4240–MAX4244 family operates from either a single +1.8V to +5.5V supply or dual ±0.9V to ±2.75V supplies. For single-supply operation, bypass the power supply with a 100nF capacitor to VEE (in this
case GND). For dual-supply operation, both the VCC Figure 8a Using a Resistor to Isolate a Capacitive Load from
the Op Amp
MAX4240-44 fig08b
MAX4240-44 fig08c
50mV/div
IN
50mV/div
IN
50mV/div
OUT
50mV/div
OUT
100s/div
RISO=NONE,RL=100kΩ,CL=700pF
100s/div
RISO=1kΩ,RL=100kΩ,CL=700pF
Figure 8b. Pulse Response without Isolating Resistor Figure 8c. Pulse Response with Isolating Resistor
Using the MAX4240–MAX4244
as Comparators Although optimized for use as operational amplifiers, the MAX4240–MAX4244 can also be used as rail-to-rail I/O comparators. Typical propagation delay depends on the input overdrive voltage, as shown in Figure 9. External hysteresis can be used to minimize the risk of output oscillation. The positive feedback circuit, shown in Figure 10, causes the input threshold to change when the output voltage changes state. The two thresh- olds create a hysteresis band that can be calculated by the following equations:
VHYST = VHI - VLO
VLO = VIN x R2 / (R1 + (R1 x R2 / RHYST) + R2)
VHI = [(R2 / R1 x VIN) + (R2 / RHYST) x VCC] / (1 + R1 / R2 + R2 / RHYST)
VOH
HYSTERESIS
VLO
VHI
INPUT VOH
10,000
MAX4240-44 fig09
The MAX4240–MAX4244 contain special circuitry to boost internal drive currents to the amplifier output stage. This maximizes the output voltage range over which the amplifiers are linear. In an open-loop com- parator application, the excursion of the output voltage is so close to the supply rails that the output stage tran- sistors will saturate, causing the quiescent current to increase from the normal 10µA. Typical quiescent cur- rents increase to 35µA for the output saturating at VCC and 28µA for the output at VEE.
Using the MAX4240–MAX4244 as Ultra-Low-Power Current Monitors
The MAX4240–MAX4244 are ideal for applications powered from a 2-cell battery stack. Figure 11 shows an application circuit in which the MAX4240 is used for monitoring the current of a 2-cell battery stack. In this circuit, a current load is applied, and the voltage drop at the battery terminal is sensed.
The voltage on the load side of the battery stack is equal to the voltage at the emitter of Q1, due to the feedback loop containing the op amp. As the load cur- rent increases, the voltage drop across R1 and R2 increases. Thus, R2 provides a fraction of the load cur- rent (set by the ratio of R1 and R2) that flows into the emitter of the PNP transistor. Neglecting PNP base cur- rent, this current flows into R3, producing a ground-ref- erenced voltage proportional to the load current. Scale R1 to give a voltage drop large enough in comparison to VOS of the op amp, in order to minimize errors.
The output voltage of the application can be calculated using the following equation:
VOUT = [ILOAD x (R1 / R2)] x R3
For a 1V output and a current load of 50mA, the choice of resistors can be R1 = 2Ω, R2 = 100kΩ, R3 = 1MΩ. The circuit consumes less power (but is more suscepti- ble to noise) with higher values of R1, R2, and R3.
1000
tPD+;VCC=+5V
OUTPUT
VOL
tPD-;VCC=+5V
VIN
RHYST
100
R1
tPD-;VCC=+1.8V
VOUT
10
0 10 20 30 40 50 60 70 80 90 100
VOD(mV)
R2
VEE
MAX4240 MAX4241 MAX4242 MAX4243 MAX4244
VEE
VCC
tPD+;VCC=+1.8V
tPD(s)
Figure 9. Propagation Delay vs. Input Overdrive Figure 10. Hysteresis Comparator Circuit
ILOAD
R1
VCC
R2
Q1
VOUT
R3
MAX4240
VEE
Chip Infor mation
MAX4240/MAX4241
TRANSISTOR COUNT: 234
MAX4242/MAX4243
TRANSISTOR COUNT: 466
MAX4244
TRANSISTOR COUNT: 932 SUBSTRATE CONNECTED TO VEE
Figure 11. Current Monitor for a 2-Cell Battery Stack
Pin Configurations (continued)
7
TOPVIEW
N.C. IN- IN+ VEE
1
2
3
4
SO/MAX
SHDN VCC OUT N.C.
OUTA INA- INA+ VEE
1
2
3
4
5
MAX4241
SO/MAX
VCC OUTB INB-
5
6
7
8
MAX4242
INB+
OUTA 1
INA- 2
6
8
INA+ | 3 | 8 | INB- | |
VEE | 4 | 7 | INB+ | |
SHDNA | 5 | 6 | SHDNB | |
MAX |
MAX4243
10 VCC
9 OUTB
OUTA | 1 | 14 | VCC | OUTA | 1 | 14 | OUTD | ||||||
INA- | 2 | 13 | OUTB | INA- | 2 | 13 | IND- | ||||||
INA+ | 3 | 12 | INB- | INA+ | 3 | 12 | IND+ | ||||||
VEE | 4 | MAX4243 | 11 | INB+ | VCC | 4 | MAX4244 | 11 | VEE | ||||
N.C. | 5 | 10 | N.C. | INB+ | 5 | 10 | INC+ | ||||||
SHDNA | 6 | 9 | SHDNB | INB- | 6 | 9 | INC- | ||||||
N.C. | 7 | 8 | N.C. | OUTB | 7 | 8 | OUTC | ||||||
SO | SO |
E D P0
P2 W B0
t
F D1
NOTE: DIMENSIONS ARE IN MM. AND FOLLOW EIA481-1 STANDARD.
P
K0
A0
5 SOT23-5
A0 | 3.200 | 0.102 | E | 1.753 | 0.102 | P0 | 3.988 | 0.102 | ||
B0 | 3.099 | 0.102 | F | 3.505 | 0.051 | P010 | 40.005 | 0.203 | ||
D 1.499 +0.102 K0 | 1.397 | 0.102 | P2 | 2.007 0.051 | ||||||
+0.254 P | 3.988 | 0.102 | t | 0.254 0.127 | ||||||
D1 0.991 +0.000 | W | 8.001 +0.305 -0.102 |
+0.000
SOT-23 5L .EPS
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
Pages changed at Rev 3: 1, 8, 9, 16
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