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

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.


MAX4240–MAX424 4

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



MAX4240–MAX424 4

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

MAX4240–MAX424

(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


MAX4240–MAX424 4

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


MAX4240–MAX424

4

(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)


MAX4240–MAX424 4

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)

Single/Dual/Quad, +1.8V/10µA, SOT23, Beyond-the-Rails Op Amps

MAX4240–MAX4244

GAIN (dB)

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.)



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

Single/Dual/Quad, +1.8V/10µA, SOT23,

Beyond-the-Rails Op Amps

MAX4240–MAX4244

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.)


Pin Description


9


Detailed Description

MAX4240–MAX424

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

MAX4240–MAX424 4

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–MAX424

4

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


MAX4240–MAX424 4

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


4

Using the MAX4240–MAX4244

MAX4240–MAX424

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

MAX4240–MAX424 4

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





Single/Dual/Quad, +1.8V/10µA, SOT23, Beyond-the-Rails Op Amps

MAX4240–MAX4244

Tape-and-Reel Information


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


Package Information

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.)










Revision History

Pages changed at Rev 3: 1, 8, 9, 16



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© 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products. Inc.

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