Datasheet

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General Description

The MAX9945 operational amplifier features an excellent

combination of low operating power and low input volt-

age noise. In addition, MOS inputs enable the MAX9945

to feature low input bias currents and low input current

noise. The device accepts a wide supply voltage range

from 4.75V to 38V and draws a low 400µA quiescent cur-

rent. The MAX9945 is unity-gain stable and is capable of

rail-to-rail output voltage swing.

The MAX9945 is ideal for portable medical and industri-

al applications that require low noise analog front-ends

for performance applications such as photodiode trans-

impedance and chemical sensor interface circuits.

The MAX9945 is available in both an 8-pin µMAX

and

a space-saving, 6-pin TDFN package, and is specified

over the automotive operating temperature range

(-40°C to +125°C).

Applications

Medical Pulse Oximetry

Photodiode Sensor Interface

Industrial Sensors and Instrumentation

Chemical Sensor Interface

High-Performance Audio Line Out

Active Filters and Signal Processing

Features

o +4.75V to +38V Single-Supply Voltage Range

o ±2.4V to ±19V Dual-Supply Voltage Range

o Rail-to-Rail Output Voltage Swing

o 400µA Low Quiescent Current

o 50fA Low Input Bias Current

o 1fA/

√

Hz Low Input Current Noise

o 15nV/

√

Hz Low Noise

o 3MHz Unity-Gain Bandwidth

o Wide Temperature Range from -40°C to +125°C

o Available in Space-Saving, 6-Pin TDFN Package

(3mm x 3mm)

MAX9945

38V, Low-Noise, MOS-Input,

Low-Power Op Amp

________________________________________________________________

Maxim Integrated Products

19-4398; Rev 1; 12/10

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART TEMP RANGE

PIN-

PACKAGE

TOP

MARK

MAX9945ATT+ -40°C to +125°C 6 TDFN-EP* AUE

MAX9945AUA+ -40°C to +125°C 8 µMAX —

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

IN-

IN+

OUT

PHOTODIODE

SIGNAL

CONDITIONING/

FILTERS

ADC

MAX9945

Typical Operating Circuit

Summary of content (14 pages)

PAGE 1
9-4398; Rev 1; 12/10 38V, Low-Noise, MOS-Input, Low-Power Op Amp The MAX9945 operational amplifier features an excellent combination of low operating power and low input voltage noise. In addition, MOS inputs enable the MAX9945 to feature low input bias currents and low input current noise. The device accepts a wide supply voltage range from 4.75V to 38V and draws a low 400µA quiescent current. The MAX9945 is unity-gain stable and is capable of rail-to-rail output voltage swing.
PAGE 2
MAX9945 38V, Low-Noise, MOS-Input, Low-Power Op Amp ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to VEE) ..................................-0.3V to +40V IN+, IN-, OUT Voltage......................(VEE - 0.3V) to (VCC + 0.3V) IN+ to IN- .............................................................................±12V OUT Short Circuit to Ground Duration....................................10s Continuous Input Current into Any Pin .............................
PAGE 3
8V, Low-Noise, MOS-Input, Low-Power Op Amp (VCC = +15V, VEE = -15V, VIN+ = VIN- = VGND = 0V, ROUT = 100kΩ to GND, TA = -40°C to +125°C, typical values are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER Output Voltage Low Output Voltage High SYMBOL VOL VOH CONDITIONS MIN TYP MAX VEE + 0.45 VEE + 0.15 ROUT = 10kΩ to GND TA = TMIN to TMAX VEE + 0.26 ROUT = 100kΩ to GND TA = TMIN to TMAX VEE + 0.05 ROUT = 10kΩ to GND TA = TMIN to TMAX VCC 0.45 VCC 0.24 TA = TMIN to TMAX VCC 0.
PAGE 4
Typical Operating Characteristics (VCC = +15V, VEE = -15V, VIN+ = VIN- = VGND = 0V, ROUT = 100kΩ to GND, TA = -40°C to +125°C, typical values are at TA = +25°C, unless otherwise noted.) TA = +125°C 400 0.15 ISINK = 1.0mA 0.10 TA = +25°C MAX9945 toc03 0.20 VCC - VOH (V) 0.20 500 0.25 MAX9945 toc02 MAX9945 toc01 0.25 VOL - VEE (V) SUPPLY CURRENT (µA) 600 OUTPUT VOLTAGE SWING HIGH vs. TEMPERATURE OUTPUT VOLTAGE SWING LOW vs. TEMPERATURE QUIESCENT SUPPLY CURRENT vs.
PAGE 5
38V, Low-Noise, MOS-Input, Low-Power Op Amp INPUT OFFSET VOLTAGE vs. TEMPERATURE INPUT OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE 600 400 200 MAX9945 toc10 800 1000 VCM = VCC - 1.2V INPUT OFFSET VOLTAGE (µV) MAX9945 toc09 INPUT OFFSET VOLTAGE (μV) 1000 800 600 VCM = 0V 400 200 VCM = VEE 0 0 -10 -5 0 5 -40 -20 10 20 40 60 80 100 120 TEMPERATURE (°C) OPEN-LOOP GAIN vs. FREQUENCY COMMON-MODE REJECTION RATIO vs.
PAGE 6
Typical Operating Characteristics (continued) (VCC = +15V, VEE = -15V, VIN+ = VIN- = VGND = 0V, ROUT = 100kΩ to GND, TA = -40°C to +125°C, typical values are at TA = +25°C, unless otherwise noted.) OP-AMP STABILITY vs. CAPACITIVE AND RESISTIVE LOADS OUTPUT IMPEDANCE vs. FREQUENCY OUTPUT IMPEDANCE (Ω) UNSTABLE 1000 STABLE 100 1000.00 MAX9945 toc16 MAX9945 toc15 PARALLEL LOAD CAPACITANCE (pF) 10,000 100.00 10.00 ACL = 10 1.00 ACL = 1 0.10 0.
PAGE 7
38V, Low-Noise, MOS-Input, Low-Power Op Amp PIN NAME FUNCTION TDFN-EP µMAX 1 6 OUT Amplifier Output 2 4 VEE Negative Power Supply. Bypass VEE with 0.1µF ceramic and 4.7µF electrolytic capacitors to quiet ground plane if different from VEE. 3 3 IN+ Noninverting Amplifier Input Inverting Amplifier Input 4 2 IN- 5 1, 5, 8 N.C. No Connection. Not internally connected. 6 7 VCC Positive Power Supply. Bypass VCC with 0.1µF ceramic and 4.
PAGE 8
MAX9945 38V, Low-Noise, MOS-Input, Low-Power Op Amp + 1 8 2 7 3 6 IN4 + MAX9945 IN+ MAX9945 5 μMAX VOUT - Figure 1. Shielding the Inverting Input to Reduce Leakage For voltage-output sensors, a noninverting amplifier is typically used to buffer and/or apply a small gain to, the input voltage signal. Due to the extremely high impedance of the sensor output, a low input bias current with a small temperature variation is very important for these applications.
PAGE 9
38V, Low-Noise, MOS-Input, Low-Power Op Amp Chip Information PROCESS: BiCMOS _______________________________________________________________________________________ 9 MAX9945 Input Differential Voltage Protection During normal op-amp operation, the inverting and noninverting inputs of the MAX9945 are at approximately the same voltage. The ±12V absolute maximum input differential voltage rating offers sufficient protection for most applications.
PAGE 10
38V, Low-Noise, MOS-Input, Low-Power Op Amp MAX9945 Pin Configurations TOP VIEW + + N.C. 1 8 N.C. IN- 2 7 VCC 3 6 OUT VEE 4 5 N.C. MAX9945 IN+ µMAX 10 OUT 1 VEE 2 IN+ 3 MAX9945 6 VCC 5 N.C.
PAGE 11
38V, Low-Noise, MOS-Input, Low-Power Op Amp PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 6 TDFN-EP T633+2 21-0137 90-0058 8 µMAX U8+1 21-0036 90-0092 ______________________________________________________________________________________ 11 MAX9945 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only.
PAGE 12
MAX9945 38V, Low-Noise, MOS-Input, Low-Power Op Amp Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. COMMON DIMENSIONS 12 PACKAGE VARIATIONS MIN. MAX. PKG. CODE N D2 E2 e JEDEC SPEC b A 0.70 0.80 T633-2 6 1.50±0.
PAGE 13
38V, Low-Noise, MOS-Input, Low-Power Op Amp α α ______________________________________________________________________________________ 13 MAX9945 Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
PAGE 14
MAX9945 38V, Low-Noise, MOS-Input, Low-Power Op Amp Revision History REVISION NUMBER REVISION DATE 0 2/09 Initial release 1 12/10 Updated Input Bias Current spec in the Electrical Characteristics table and updated Note 3 DESCRIPTION PAGES CHANGED — 2, 3 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.