Rainbow Electronics MAX495 User Manual

19-0265; Rev 2; 9/96

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

_______________General Description

The dual MAX492, quad MAX494, and single MAX495 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 150µA supply current. Even with this low current, the op amps are capable of driving a 1kΩ load, and the input referred voltage noise is only 25nV/√Hz. In addition, these op amps can drive loads in excess of 1nF.

The precision performance of the MAX492/MAX494/ MAX495, combined with their wide input and output dynamic range, low-voltage single-supply operation, and very low supply current, makes them an ideal choice for battery-operated equipment and other low-voltage applications. The MAX492/MAX494/MAX495 are available in DIP and SO packages in the industry-standard op-amp pin configurations. The MAX495 is also available in the smallest 8-pin SO: the µMAX package.

________________________Applications

Portable Equipment Battery-Powered Instruments Data Acquisition Signal Conditioning Low-Voltage Applications

____________________________Features

♦ Low-Voltage Single-Supply Operation (+2.7V to +6V) ♦ Rail-to-Rail Input Common-Mode Voltage Range ♦ Rail-to-Rail Output Swing ♦ 500kHz Gain-Bandwidth Product ♦ Unity-Gain Stable ♦ 150µA Max Quiescent Current per Op Amp ♦ No Phase Reversal for Overdriven Inputs ♦ 200µV Offset Voltage ♦ High Voltage Gain (108dB) ♦ High CMRR (90dB) and PSRR (110dB) ♦ Drives 1kΩ Load ♦ Drives Large Capacitive Loads ♦ MAX495 Available in µMAX Package—8-Pin SO

______________Ordering Information

PART

MAX492CPA

MAX492CSA MAX492C/D 0°C to +70°C MAX492EPA MAX492ESA -40°C to +85°C MAX492MJA -55°C to +125°C 8 CERDIP

Ordering Information continued at end of data sheet.

Dice are specified at TA = +25°C, DC parameters only.

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

-40°C to +85°C 8 Plastic DIP

8 Plastic DIP 8 SO Dice*

8 SO

MAX492/MAX494/MAX495

__________Typical Operating Circuit

+5V

10k

MAX495

ANALOG

INPUT

10k

INPUT SIGNAL CONDITIONING FOR LOW-VOLTAGE ADC

________________________________________________________________

AIN

MAX187

(ADC)

GND

DOUT

SCLK

SHDN

REF

6 8 7

3 4

SERIAL INTERFACE

4.096V

_________________Pin Configurations

TOP VIEW

OUT1

IN1-

IN1+

NULL

IN1-

IN1+

MAX492

DIP/SO

MAX495

2 3 4

DIP/SO/µMAX

Pin Configurations continued at end of data sheet.

Maxim Integrated Products

OUT2

IN2-

IN2+

N.C.

OUT

NULL

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (VCCto VEE)....................................................7V

Common-Mode Input Voltage..........(V

Differential Input Voltage .........................................±(V

Input Current (IN+, IN-, NULL1, NULL2)..........................±10mA

Output Short-Circuit Duration ....................Indefinite short circuit

Voltage Applied to NULL Pins....................................V

Continuous Power Dissipation (TA= +70°C)

8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ....727mW

8-Pin SO (derate 5.88mW/°C above +70°C).................471mW

8-Pin CERDIP (derate 8.00mW/°C above +70°C).........640mW

8-Pin µMAX (derate 4.1mW/°C above +70°C)..............330mW

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.

+ 0.3V) to (VEE- 0.3V)

to either supply

- VEE)

to V

DC ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6V, VEE= GND, VCM= 0V, V

OUT

= V

/ 2, TA= +25°C, unless otherwise noted.)

14-Pin Plastic DIP (derate 10.00mW/°C above +70°C)...800mW

14-Pin SO (derate 8.33mW/°C above +70°C)...............667mW

14-Pin CERDIP (derate 9.09mW/°C above +70°C).......727mW

Operating Temperature Ranges

MAX49_C_ _ ........................................................0°C to +70°C

MAX49_E_ _......................................................-40°C to +85°C

MAX49_M_ _...................................................-55°C to +125°C

Junction Temperatures

MAX49_C_ _/E_ _..........................................................+150°C

MAX49_M_ _.................................................................+175°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10sec).............................+300°C

CONDITIONS

VCM= VEEto V

Input Bias Current

MAX492/MAX494/MAX495

Common-Mode Input Voltage Range

Common-Mode Rejection Ratio dB

Large-Signal Voltage Gain (Note 1)

Output Voltage Swing (Note 1)

Supply Current (per amplifier)

VCM= VEEto V

= VEEto V

(VEE- 0.25V) ≤ VCM≤ (VCC+ 0.25V) VCC= 2.7V to 6V

VCC= 2.7V,

= 100kΩ,

= 0.25V to 2.45V

OUT

VCC= 2.7V, RL= 1kΩ, V

= 0.5V to 2.2V

OUT

VCC= 5.0V,

= 100kΩ,

= 0.25V to 4.75V

OUT

VCC= 5.0V, RL= 1kΩ, V

= 0.5V to 4.5V

OUT

RL= 100kΩ

RL= 1kΩ

VCM= V

OUT

= V

CC CC CC

74 90

Sourcing Sinking Sourcing Sinking 78 90 Sourcing Sinking 92 100 Sourcing Sinking 86 98 V

VCC= 2.7V

/ 2

VCC= 5V

90 104 90 102 94 105

98 108

98 110

VCC- 0.075 VCC- 0.04

VCC- 0.20 VCC- 0.15

VEE+ 0.04 VEE+ 0.075

VEE+ 0.15 VEE+ 0.20

135 150 150 170

UNITSMIN TYP MAXPARAMETER

µV±200 ±500Input Offset Voltage nA±25 ±60 nA±0.5 ±6Input Offset Current

MΩ2Differential Input Resistance

VVEE- 0.25 VCC+ 0.25

dB88 110Power-Supply Rejection Ratio

mA30Output Short-Circuit Current

V2.7 6.0Operating Supply Voltage Range

µA

2 _______________________________________________________________________________________

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

AC ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6V, VEE= GND, TA= +25°C, unless otherwise noted.)

CONDITIONS

RL= 100kΩ, CL= 100pF

Gain Margin

Turn-On Time

Input Noise-Current Density

RL= 100kΩ, CL= 100pF RL= 100kΩ, CL= 100pF RL= 10kΩ, CL= 15pF, V RL= 100kΩ, CL= 15pF To 0.1%, 2V step VCC= 0V to 3V step, VIN= V f = 1kHz f = 1kHz f = 1kHz dB125Amp-Amp Isolation

OUT

= 2V

p-p

/ 2, AV= +1

60Phase Margin

, AV= +1, f = 1kHz

25Input Noise-Voltage Density

degrees

DC ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6V, VEE= GND, VCM= 0V, V

VCM= VEEto V

Input Bias Current

Common-Mode Input Voltage Range Common-Mode Rejection Ratio dB

Power-Supply Rejection Ratio

Large-Signal Voltage Gain (Note 1)

Output Voltage Swing (Note 1)

Supply Current (per amplifier)

VCM= VEEto V VCM= VEEto V

(VEE- 0.20) ≤ VCM≤ (VCC+ 0.20) VCC= 2.7V to 6V

VCC= 2.7V, RL= 100kΩ, V

OUT

VCC= 2.7V, RL= 1kΩ, V

OUT

VCC= 5.0V, RL= 100kΩ, V

OUT

VCC= 5.0V, RL= 1kΩ, V

OUT

RL= 100kΩ

RL= 1kΩ

VCM= V

= V

OUT

= 0.25V to 2.45V

= 0.5V to 2.2V

= 0.25V to 4.75V

= 0.5V to 4.5V

OUT

/ 2, TA= 0°C to +70°C, unless otherwise noted.)

CC CC

= V

/ 2

CONDITIONS

Sourcing Sinking Sourcing Sinking 76 Sourcing Sinking 88 Sourcing Sinking V

VCC= 2.7V VCC= 5V

88 84 92

96 82

VCC- 0.075

VEE+ 0.075

VCC- 0.20

VEE+ 0.20

175 190

MAX492/MAX494/MAX495

UNITSMIN TYP MAXPARAMETER

kHz500Gain-Bandwidth Product

dB10

%0.003Total Harmonic Distortion

V/µs0.20Slew Rate

µs12Time µs

nV/√Hz

pA/√Hz0.1

UNITSMIN TYP MAXPARAMETER

µV±650Input Offset Voltage

µV/°C±2Input Offset Voltage Tempco

nA±75 nA±6Input Offset Current

VVEE- 0.20 VCC+ 0.20

dB86

V2.7 6.0Operating Supply Voltage Range

µA

_______________________________________________________________________________________ 3

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

DC ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6V, VEE= GND, VCM= 0V, V

VCM= VEEto V

Input Bias Current

Common-Mode Input Voltage Range

Large-Signal Voltage Gain (Note 1)

MAX492/MAX494/MAX495

Output Voltage Swing (Note 1)

Operating Supply-Voltage Range 2.7 6.0 V Supply Current (per amplifier) VCM= V

VCM= VEEto V VCM= VEEto V

(VEE- 0.15) ≤ VCM≤ (VCC+ 0.15) VCC= 2.7V to 6V, VCM= 0V

VCC= 2.7V, RL= 100kΩ, V

OUT

VCC= 2.7V, RL= 1kΩ, V

OUT

VCC= 5.0V, RL= 100kΩ, V

OUT

VCC= 5.0V, RL= 1kΩ, V

OUT

RL= 100kΩ

RL= 1kΩ

= V

OUT

= 0.25V to 2.45V

= 0.5V to 2.2V

= 0.25V to 4.75V

= 0.5V to 4.5V

OUT

/ 2, TA= -40°C to +85°C, unless otherwise noted.)

CC CC

= VCC/ 2

CONDITIONS

Sourcing Sinking Sourcing Sinking Sourcing Sinking Sourcing Sinking V

VCC= 2.7V VCC= 5V

±2Input Offset Voltage Tempco

86 84 92 76 92 86 96 80

VCC- 0.075

VEE+ 0.075

VCC- 0.20

VEE+ 0.20

185 200

UNITSMIN TYP MAXPARAMETER

µV±950Input Offset Voltage

µV/°C

nA±100 nA±8Input Offset Current

VVEE- 0.15 VCC+ 0.15

dBCommon-Mode Rejection Ratio dB84Power-Supply Rejection Ratio

µA

4 _______________________________________________________________________________________

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

DC ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6V, VEE= GND, VCM= 0V, V

VCM= VEEto V

Input Bias Current

Power-Supply Rejection Ratio

Large-Signal Voltage Gain (Note 1)

Output Voltage Swing (Note 1)

Supply Current (per amplifier)

VCM= VEEto V VCM= VEEto V

(VEE- 0.05V) ≤ VCM≤ (VCC+ 0.05V) VCC= 2.7V to 6V

VCC= 2.7V, RL= 100kΩ, V

OUT

VCC= 2.7V, RL= 1kΩ, V

OUT

VCC= 5.0V, RL= 100kΩ, V

OUT

VCC= 5.0V, RL= 1kΩ, V

OUT

RL= 100kΩ

RL= 1kΩ

VCM= V

= V

OUT

CC CC

= 0.25V to 2.45V

= 0.5V to 2.2V

= 0.25V to 4.75V

= 0.5V to 4.5V

= VCC/ 2

OUT

/ 2, TA= -55°C to +125°C, unless otherwise noted.)

CONDITIONS

Sourcing Sinking Sourcing Sinking 72 Sourcing Sinking 82 Sourcing Sinking V

VCC= 2.7V VCC= 5V

82 80 90

94 76

VCC- 0.075

VCC- 0.250

±2Input Offset Voltage Tempco

VEE+ 0.075

VEE+ 0.250

200 225

MAX492/MAX494/MAX495

UNITSMIN TYP MAXPARAMETER

mV±1.2Input Offset Voltage

µV/°C

nA±200 nA±10Input Offset Current

VVEE- 0.05 VCC+ 0.05Common-Mode Input Voltage Range dBCommon-Mode Rejection Ratio dB80

V2.7 6.0Operating Supply-Voltage Range µA

Note 1: RLto VEEfor sourcing and VOHtests; RLto VCCfor sinking and VOLtests.

_______________________________________________________________________________________ 5

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

__________________________________________Typical Operating Characteristics

(TA = +25°C, VCC= 5V, VEE= 0V, unless otherwise noted.)

GAIN AND PHASE

vs. FREQUENCY

GAIN (dB)

-20

-40

0.01 10 10,000

PHASE

AV = +1000 NO LOAD

0.1 1 100 1000

GAIN

FREQUENCY (kHz)

MAX492-01

180

120

-60

-120

-180

GAIN (dB)

PHASE (DEG)

CL = 470pF

-20 A

-40

0.01 10 10,000

CHANNEL SEPARATION 

vs. FREQUENCY

140

MAX492/MAX494/MAX495

120

100

CHANNEL SEPARATION (dB)

VIN = 2.5V

0.01 10 10,000

0.1 1 100 1000 FREQUENCY (kHz)

MAX492-04

160 140 120 100

80 60

OFFSET VOLTAGE (µV)

40 20

-60 -20 60 140

GAIN AND PHASE

vs. FREQUENCY

GAIN

PHASE

= +1000

= ∞

0.1 1 100 1000 FREQUENCY (kHz)

OFFSET VOLTAGE 

vs. TEMPERATURE

-40 0 40 80 120

20 100

TEMPERATURE (°C)

VCM = 0V

MAX492-02

180

120

-60

-120

-180

MAX492-05

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

140 120

100

80 60

PSRR (dB)

PHASE (DEG)

40 20

VIN = 2.5V

-20

0.01 10 1000

0.1 1 100 FREQUENCY (kHz)

COMMON-MODE REJECTION RATIO 

vs. TEMPERATURE

120

VCM = 0V TO +5V

110

= -01V TO +5.1V

100

CMRR (dB)

VCM = -0.2V TO +5.2V

= -0.3V TO +5.3V

= -0.4V TO +5.4V

-40 0 40 80 120

-60 -20 60 140

20 100

TEMPERATURE (°C)

MAX492-03

MAX492-06

INPUT BIAS CURRENT

vs. COMMON-MODE VOLTAGE

20 15

= 2.7V

5 0

-5

-10

-15

INPUT BIAS CURRENT (nA)

-20

-25

-30 02 6

1357

VCC = 6V

VCM (V)

125 100

MAX492-07

75 50 25

-25

-50

INPUT BIAS CURRENT (nA)

-75

-100

-125

-60 0 100

INPUT BIAS CURRENT

vs. TEMPERATURE

VCC = 6V

VCM = V

VCC = 2.7V

VCM = 0

VCC = 6V

-20 20 80 120 TEMPERATURE (°C)

SUPPLY CURRENT PER AMPLIFIER

vs. TEMPERATURE

220

= VCM = VCC/2

OUT

MAX492-08

140-40 40

200 180 160 140 120 100

80 60 40

SUPPLY CURRENT PER OP AMP (µA)

VCC = 5V

-40 0 40 80 120

-60 -20 60 140 TEMPERATURE (°C)

6 _______________________________________________________________________________________

MAX492-09

VCC = 2.7V

20 100

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, VCC= 5V, VEE= 0V, unless otherwise noted.)

200

VCC - V

RL = 1kΩ

OUT



(mV)

OUT



RL = 100kΩ

VCC = +6V

TO V

(mV)



= 100kΩ

RL = 10kΩ

RL = 1MΩ

500

RL = 1MΩ

RL = 1kΩ

VCC = +6V

TO V

500

RL = 1MΩ

200

VCC - V



RL = 1kΩ

OUT



RL = 1MΩ

(mV)

OUT

RL = 100kΩ

RL = 10kΩ

VCC = +2.7V

TO V

(mV)

RL = 10kΩ

VCC = +2.7V R

500

RL = 1kΩ

TO V

500

LARGE-SIGNAL GAIN

vs. TEMPERATURE

120

MAX492-11

115 110 105 100

95 90

LARGE-SIGNAL GAIN (dB)

85 80

RL = 1kΩ, 0.5V < V

RL TO V

VCC = +2.7V

RL TO V

-40 0 40 80 120

-60 -20 60 140

20 100

TEMPERATURE (°C)

< (VCC - 0.5V)

OUT

VCC = +6V

LARGE-SIGNAL GAIN

vs. TEMPERATURE

120

MAX492-14

110 105 100

95 90

LARGE-SIGNAL GAIN (dB)

85 80

RL TO V

-40 0 40 80 120

-60 -20 60 140

20 100

TEMPERATURE (°C)

RL = 100kΩ, 0.3V < V

115

< (VCC - 0.3V)

OUT

VCC = +6V

VCC = +2.7V

LARGE-SIGNAL GAIN

vs. OUTPUT VOLTAGE

120

MAX492-10

110

100



GAIN (dB)

60 50

0 100 300 400 600

LARGE-SIGNAL GAIN

vs. OUTPUT VOLTAGE

120

MAX492-13

110

100

 GAIN (dB)



= 100kΩ

100

0 200 300 400 600

LARGE-SIGNAL GAIN

vs. OUTPUT VOLTAGE

120

110

100



GAIN (dB)

60 50

RL = 10kΩ

0 100 300 400 600

LARGE-SIGNAL GAIN

vs. OUTPUT VOLTAGE

120 110

100



GAIN (dB)

100

0 200 300 400 600

MAX492/MAX494/MAX495

MAX492-12

MAX492-15

MINIMUM OUTPUT VOLTAGE

vs. TEMPERATURE

220

RL TO V

200 180 160 140 120

MIN (mV)

100

OUT

60 40 20

VCC = 6V, RL = 1kΩ

VCC = 2.7V, RL = 1kΩ

VCC = 6V, RL = 100kΩ

VCC = 2.7V, RL = 100kΩ

-60 140

080

-40 -20 20 40 60 100 120 TEMPERATURE (°C)

_______________________________________________________________________________________

MAX492-16

MAXIMUM OUTPUT VOLTAGE

vs. TEMPERATURE

200

RL TO V

180 160 140 120

) (mV)

OUT

100

- V

60 40 20

-60 140

VCC = 6V, RL = 1kΩ

VCC = 2.7V, RL = 1kΩ

VCC = 6V, RL = 100kΩ

VCC = 2.7V, RL = 100kΩ

080

-40 -20 20 40 60 100 120 TEMPERATURE (°C)

MAX492-17

OUTPUT IMPEDANCE

vs. FREQUENCY

1000

VCM = V

100

OUTPUT IMPEDANCE (Ω)

0.1

0.01 10 10,000

= 2.5V

OUT

0.1 1 100 1,000 FREQUENCY (kHz)

MAX492-18

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, VCC= 5V, VEE= 0V, unless otherwise noted.)

VOLTAGE-NOISE DENSITY

vs. FREQUENCY

100

MAX492-19

VOLTAGE-NOISE DENSITY (nV/√Hz)

INPUT REFERRED

0.01  1

0.1 10 FREQUENCY (kHz)

TOTAL HARMONIC DISTORTION + NOISE

0.1 AV = +1

MAX492/MAX494/MAX495

2V 80kHz LOWPASS FILTER

0.01

THD + NOISE (%)

0.001 10  1000

vs. FREQUENCY

SIGNAL

P-P

RL = 10kΩ TO GND

100 10,000

FREQUENCY (Hz)

MAX492-21

NO LOAD

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

0.01  1

0.1 10 FREQUENCY (kHz)

TOTAL HARMONIC DISTORTION + NOISE vs. PEAK-TO-PEAK SIGNAL AMPLITUDE

0.1 AV = +1

1kHz SINE 22kHz FILTER

TO GND

0.01

THD + NOISE (%)

0.001

4.0 4.2 4.7 PEAK-TO-PEAK SIGNAL AMPLITUDE (V)

RL = 1kΩ

RL = 2kΩ

4.3 5.04.1 4.4 4.5 4.6 4.8 4.9

MAX492-20

MAX492-22

RL = 100kΩ

RL = 10kΩ

SMALL-SIGNAL TRANSIENT RESPONSE

VIN 50mV/div

OUT

50mV/div

2µs/div

VCC = +5V, AV = +1, RL = 10kΩ

VCC = +5V, AV = -1, RL = 10kΩ

2µs/div

8 _______________________________________________________________________________________

VIN 50mV/div

OUT

50mV/div

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, VCC= 5V, VEE= 0V, unless otherwise noted.)

LARGE-SIGNAL TRANSIENT RESPONSE

50µs/div

= +5V, AV = +1, RL = 10kΩ

VIN 2V/div

OUT

2V/div

LARGE-SIGNAL TRANSIENT RESPONSE

50µs/div

VCC = +5V, AV = -1, RL = 10kΩ

VIN 2V/div

OUT

2V/div

______________________________________________________________Pin Description

MAX492

MAX494

1 — —

2 —

5 —

10 12 13 14

—

MAX495

—

1, 5

—

6 — —

7 — — — — — —

NAME

NULL—

Amplifier 1 OutputOUT11 Offset Null Input. Connect to a 10kΩ potentiometer for offset-voltage trimming.

Connect wiper to VEE(Figure 3). Inverting InputIN-—

Amplifier 1 Inverting InputIN1-2 Noninverting InputIN+— Amplifier 1 Noninverting InputIN1+3 Negative Power-Supply Pin. Connect to ground or a negative voltage.V Amplifier 2 Noninverting InputIN2+5 Amplifier OutputOUT— Amplifier 2 Inverting InputIN2-6 Amplifier 2 OutputOUT27 Positive Power-Supply Pin. Connect to (+) terminal of power supply.V Amplifier 3 OutputOUT3— Amplifier 3 Inverting InputIN3-— Amplifier 3 Noninverting InputIN3+— Amplifier 4 Noninverting InputIN4+— Amplifier 4 Inverting InputIN4-— Amplifier 4 OutputOUT4— No Connect. Not internally connected.N.C.—

FUNCTION

MAX492/MAX494/MAX495

_______________________________________________________________________________________ 9

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

__________Applications Information

The dual MAX492, quad MAX494, and single MAX495 op amps combine excellent DC accuracy with rail-torail 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 and other lowvoltage applications.

Rail-to-Rail Inputs and Outputs

The MAX492/MAX494/MAX495’s input common-mode range extends 0.25V 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 MAX492/MAX494/MAX495 can be used in applications with common-mode signals at or even beyond the supplies, without the problems associated with typical op amps.

The MAX492/MAX494/MAX495’s output voltage swings to within 50mV of the supplies with a 100kΩ load. This rail-to-rail swing at the input and output substantially increases the dynamic range, especially in low supplyvoltage applications. Figure 1 shows the input and out-

MAX492/MAX494/MAX495

put waveforms for the MAX492, configured as a unity-gain noninverting buffer operating from a single +3V supply. The input signal is 3.0V centered at +1.5V. The output amplitude is approximately 2.95V

p-p

, 1kHz sinusoid

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 small 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. 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.

To adjust the MAX495’s input offset voltage (500µV max at +25°C), connect a 10kΩ trim potentiometer between the two NULL pins (pins 1 and 5), with the wiper connected to VEE(pin 4) (Figure 2). The trim range of this circuit is ±6mV. External offset adjustment is not available for the dual MAX492 or quad MAX494.

The input bias currents of the MAX492/MAX494/MAX495 are typically less than 50nA. 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



10k

OUT

Figure 1. Rail-to-Rail Input and Output (Voltage Follower Circuit, VCC= +3V, VEE= 0V)

10 ______________________________________________________________________________________

Figure 2. Offset Null Circuit

NULL

MAX495

NULL

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

the op amp in an inverting configuration (Figure 3a); connect resistor R3 between the noninverting input and the input signal when using the op amp in a noninverting configuration (Figure 3b). Select R3 to equal the parallel combination of R1 and R2. High source resistances will degrade noise performance, due to the thermal noise of the resistor and the input current noise (which is multiplied by the source resistance).

Input Stage Protection Circuitry

The MAX492/MAX494/MAX495 include internal protec-

tion 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 1.7kΩ resistors in series

MAX49_

OUT

(Figure 4). 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 (±25nA typical) is specified for the small differential input voltages. For large differential input voltages (exceeding VF), this protection circuitry increases the input current at IN+ and IN-:

Input Current = ———————————

2 x 1.7kΩ

(VIN+ - VIN- ) - V

For comparator applications requiring large differential voltages (greater than VF), you can limit the input current that flows through the diodes with external resistors

MAX492 MAX494 MAX495

IN+



1.7kΩ

TO INTERNAL CIRCUITRY

MAX492/MAX494/MAX495

R3 = R2 II R1

Figure 3a. Reducing Offset Error Due to Bias Current: Inverting Configuration

MAX49_

R3 = R2 II R1

OUT

Figure 3b. Reducing Offset Error Due to Bias Current: Noninverting Configuration

______________________________________________________________________________________ 11

IN–

1.7kΩ

TO INTERNAL CIRCUITRY

Figure 4. Input Stage Protection Circuitry

10,000

UNSTABLE REGION

1000

CAPACITIVE LOAD (pF)

100

1 10 100

RESISTIVE LOAD (kΩ)

VCC = +5V

= VCC/2

OUT

TO VEE

= +1

MAX492-FG 04

Figure 5. Capacitive-Load Stable Region Sourcing Current

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

in series with IN-, IN+, or both. Series resistors are not recommended for amplifier applications, as they may increase input offsets and decrease amplifier bandwidth.

Output Loading and Stability

Even with their low quiescent current of less than 150µA per op amp, the MAX492/MAX494/MAX495 are well suited for driving loads up to 1kΩ while maintaining DC accuracy. Stability while driving heavy capacitive loads is another key advantage over comparable CMOS railto-rail op amps.

VIN 50mV/div

OUT

50mV/div

MAX492/MAX494/MAX495

10µs/div

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 enough—as when driving a large capacitive load—the circuit phase margin is degraded, leading to either an under-damped pulse response or oscillation.



50mV/div

OUT

50mV/div

10µs/div

Figure 6. MAX492 Voltage Follower with 1000pF Load

= ∞)



50mV/div

OUT

50mV/div

10µs/div

Figure 7a. MAX492 Voltage Follower with 500pF Load—

= 5k

Ω

12 ______________________________________________________________________________________

Figure 7b. MAX492 Voltage Follower with 500pF Load—

= 20k

Ω

10µs/div

Figure 7c. MAX492 Voltage Follower with 500pF Load—

∞



50mV/div

OUT

50mV/div

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

The MAX492/MAX494/MAX495 can drive capacitive loads in excess of 1000pF under certain conditions (Figure 5). When driving capacitive loads, the greatest potential for instability occurs when the op amp is sourcing approximately 100µA. Even in this case, stability is maintained with up to 400pF of output capacitance. If the output sources either more or less current, stability is increased. These devices perform well with a 1000pF pure capacitive load (Figure 6). Figure 7 shows the performance with a 500pF load in parallel with various load resistors.

MAX49_

OUT

To increase stability while driving large capacitive loads, connect a pull-up resistor at the output to decrease the current that 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 8). This resistor improves the phase margin of the circuit by isolating the load capacitor from the op amp’s output. Figure 9a shows the MAX492 driving 10,000pF (RL≥ 100kΩ), while Figure 9b adds a 47Ω isolation resistor.

VIN 50mV/div

OUT

50mV/div

MAX492/MAX494/MAX495

Figure 8. Capacitive-Load Driving Circuit

10µs/div

Figure 9a. Driving a 10,000pF Capacitive Load

VIN 50mV/div

OUT

50mV/div

10µs/div

Figure 9b. Driving a 10,000pF Capacitive Load with a 47

Isolation Resistor

+5V

MAX495

OUT

Figure 10. Power-Up Test Configuration

Ω

______________________________________________________________________________________ 13

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

VCC 1V/div

OUT

500mV/div

VCC 2V/div

OUT

1V/div

5µs/div

Because the MAX492/MAX494/MAX495 have excellent stability, no isolation resistor is required, except in the most demanding applications. This is beneficial because an isolation resistor would degrade the low-

MAX492/MAX494/MAX495

frequency performance of the circuit.

Power-Up Settling Time

The MAX492/MAX494/MAX495 have a typical supply current of 150µA 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 MAX494 to buffer the inputs to a multi-channel analog-to-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 MAX492/MAX494/ MAX495, 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 slew-rate limited. With the noninverting input to a voltage follower held at mid-supply (Figure 10), when the supply steps from 0V to VCC, the output settles in approximately 4µs for VCC= +3V (Figure 11a) or 10µs for VCC= +5V (Figure 11b).

5µs/div

Figure 11b. Power-Up Settling Time (VCC= +5V)Figure 11a. Power-Up Settling Time (VCC= +3V)

Power Supplies and Layout

The MAX492/MAX494/MAX495 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 1µF capacitor in parallel with a

0.1µF ceramic 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 amp’s inputs and output. To decrease stray capacitance, minimize both trace lengths and resistor leads and place external components close to the op amp’s pins.

Rail-to-Rail Buffers

The

Typical Operating Circuit

two buffer driving the analog input to a MAX187 12-bit ADC. Both devices run from a single 5V supply, and the converter’s internal reference is 4.096V. The MAX495’s typical input offset voltage is 200µV. This results in an error at the ADC input of 400µV, or less than half of one least significant bit (LSB). Without offset trimming, the op amp contributes negligible error to the conversion result.

shows a MAX495 gain-of-

14 ______________________________________________________________________________________

Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

_Ordering Information (continued)

PART

MAX494CPD

MAX494CSD MAX494EPD -40°C to +85°C MAX494ESD MAX494MJD -55°C to +125°C MAX495CPA MAX495CSA MAX495CUA 0°C to +70°C MAX495C/D MAX495EPA -40°C to +85°C MAX495ESA -40°C to +85°C 8 SO MAX495MJA -55°C to +125°C 8 CERDIP

* Dice are specified at TA= +25°C, DC parameters only.

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

14 Plastic DIP 14 SO 14 Plastic DIP

-40°C to +85°C 14 SO 14 CERDIP

0°C to +70°C 8 Plastic DIP 0°C to +70°C

8 SO 8 µMAX

0°C to +70°C Dice*

8 Plastic DIP

____Pin Configurations (continued)

TOP VIEW

_________________Chip Topographies

MAX492

IN1+



IN2+

NULL1

IN1-

IN2-

0.069"

(1.752mm)

MAX495

OUT1

0.068"

(1.728mm)

OUT2

MAX492/MAX494/MAX495

OUT1

IN1IN1+

V IN2+ IN2-

OUT2

IN-

1 2 3

MAX494

5 6 7

DIP/SO

OUT4

IN4-

IN4+

IN3+

IN3-

OUT3

IN+

0.055"

(1.397mm)

NULL2

0.056"

(1.422mm)

OUT

TRANSISTOR COUNT: 134 (single MAX495)

268 (dual MAX492) 536 (quad MAX494)

SUBSTRATE CONNECTED TO V

______________________________________________________________________________________ 15

Single/Dual/Quad, Micropower, Single-Supply Rail-to-Rail Op Amps

________________________________________________________Package Information

0.101mm

A1B

E H

0.004 in

8-PIN µMAX

MICROMAX SMALL-OUTLINE

PACKAGE

MAX492/MAX494/MAX495

0.101mm

0.004in.

DIM

A1

DIM

0°-8°

INCHES MILLIMETERS



MIN

A

0.036

0.004

B

0.010

C

0.005

D

0.116

E

0.116 e H

0.188 L

0.016



MIN

0.053

0.004 B

0.014 C

0.007 E

0.150 e H

0.228 L

0.016

MAX

0.044

0.008

0.014

0.007

0.120



0°

INCHES MILLIMETERS



0.198

0.026 6°

MAX

0.069

0.010

0.019

0.010

0.157

0.244

0.050

MIN

0.91

0.10

0.25

0.13

2.95

4.78

0.41 0°

MIN

1.35

0.10

0.35

0.19

3.80

5.80

0.40

MAX

1.11

0.20

0.36

0.18

3.05

0.650.0256



5.03

0.66 6°

21-0036D

MAX

1.75

0.25

0.49

0.25

4.00

1.270.050

6.20

1.27

PINS

Narrow SO

SMALL-OUTLINE

PACKAGE

(0.150 in.)

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.

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

DIM

D D D



INCHES MILLIMETERS

MIN

MAX

0.189

0.197

0.337

0.344

0.386

0.394

MIN

4.80

8.55

9.80

MAX

5.00

8.75

10.00

21-0041A

Rainbow Electronics MAX495 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual