Datasheet

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General Description

The MAX9922/MAX9923 ultra-precision, high-side cur-

rent-sense amplifiers feature ultra-low offset voltage

) of 25µV (max) and laser-trimmed gain accuracy

better than 0.5%. The combination of low V

and high-

gain accuracy allows precise current measurements

even at very small sense voltages.

The MAX9922/MAX9923 are capable of both unidirec-

tional and bidirectional operation. For unidirectional

operation, connect REF to GND. For bidirectional oper-

ation, connect REF to V

/2.

The MAX9922 has adjustable gain set with two external

resistors. The MAX9923T/MAX9923H/MAX9923F use an

internal laser-trimmed resistor for fixed gain of 25V/V,

100V/V, and 250V/V, respectively. The devices operate

from a +2.85V to +5.5V single supply, independent

of the input common-mode voltage, and draw only 700µA

operating supply current and less than 1µA in shutdown.

The +1.9V to +28V current-sense input common-mode

voltage range makes the MAX9922/MAX9923 ideal for

current monitoring in applications where high accuracy,

large common-mode measurement range, and mini-

mum full-scale V

SENSE

voltage is critical.

The MAX9922/MAX9923 use a spread-spectrum

autozeroing technique that constantly measures and

cancels the input offset voltage, eliminating drift over

time and temperature, and the effect of 1/f noise. This,

in conjunction with the indirect current-feedback tech-

nique, achieves less than 25µV (max) offset voltage.

The MAX9922/MAX9923 are available in a small 10-pin

µMAX

package and are specified over the -40°C to

+85°C extended temperature range.

Applications

Notebook/Desktop Power Management

Handheld Li+ Battery Current Monitoring

Precision Current Sources

Features

♦ Ultra-Precision V

Over Temperature

MAX9922: ±10µV (max)

MAX9923T: ±25µV (max)

MAX9923H: ±20µV (max)

MAX9923F: ±10µV (max)

♦ ±0.5% (max) Full-Scale Gain Accuracy

♦ Bidirectional or Unidirectional I

SENSE

♦ Multiple Gains Available

Adjustable (MAX9922)

+25V/V (MAX9923T)

+100V/V (MAX9923H)

+250V/V (MAX9923F)

♦ 1.9V to 28V Input Common-Mode Voltage,

Independent of V

♦ Supply Voltage: +2.85V to +5.5V

♦ 700µA Supply Current, 1µA Shutdown Current

♦ Extended Temperature Range (-40°C to +85°C)

♦ Available in Space-Saving 10-Pin µMAX

MAX9922/MAX9923

Ultra-Precision, High-Side

Current-Sense Amplifiers

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-4429; Rev 1; 1/10

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.

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

EVALUATION KIT

AVAILABLE

PART

PIN-

PACKAGE

TEMP

RANGE

GAIN (V/V)

MAX9922EUB+

10 µMAX

- 40°C to + 85° C

Adjustable

MAX9923TEUB+

10 µMAX

- 40°C to + 85° C

MAX9923HEUB+

10 µMAX

- 40°C to + 85° C

100

MAX9923FEUB+

10 µMAX

- 40°C to + 85° C

250

Pin Configuration

OUT

REFN.C.

RS-

RS+

RSB

MAX9922

MAX9923T

MAX9923H

MAX9923F

µMAX

TOP VIEW

GND

SHDN

Typical Operating Circuits appear at end of data sheet.

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

Summary of content (15 pages)

PAGE 1
9-4429; Rev 1; 1/10 KIT ATION EVALU E L B AVAILA Ultra-Precision, High-Side Current-Sense Amplifiers The MAX9922/MAX9923 ultra-precision, high-side current-sense amplifiers feature ultra-low offset voltage (VOS) of 25µV (max) and laser-trimmed gain accuracy better than 0.5%. The combination of low VOS and highgain accuracy allows precise current measurements even at very small sense voltages. The MAX9922/MAX9923 are capable of both unidirectional and bidirectional operation.
PAGE 2
MAX9922/MAX9923 Ultra-Precision, High-Side Current-Sense Amplifiers ABSOLUTE MAXIMUM RATINGS RSB, RS+, RS- to GND...........................................-0.3V to +30V VDD to GND ..............................................................-0.3V to +6V OUT, REF, FB, SHDN to GND .................-0.3V to the lower of (VDD + 0.3V) and +6V OUT Short Circuit to VDD or GND ..............................Continuous Differential Voltage (VRS+ - VRS-), (VRSB - VRS+), (VRSB - VRS-) ...............................
PAGE 3
Ultra-Precision, High-Side Current-Sense Amplifiers (VRSB = VRS+ = VRS- = +12V, VDD = +3.3V, VGND = 0V, VREF = VDD/2 for bidirectional, VREF = 0V for unidirectional, VSENSE = VRS+ - VRS= 0V, MAX9922 is set for AV =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = VDD, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
MAX9922/MAX9923 Ultra-Precision, High-Side Current-Sense Amplifiers ELECTRICAL CHARACTERISTICS (continued) (VRSB = VRS+ = VRS- = +12V, VDD = +3.3V, VGND = 0V, VREF = VDD/2 for bidirectional, VREF = 0V for unidirectional, VSENSE = VRS+ - VRS= 0V, MAX9922 is set for AV =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = VDD, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
Ultra-Precision, High-Side Current-Sense Amplifiers (VRSB = VRS+ = VRS- = +12V, VDD = +3.3V, VGND = 0V, VREF = VDD/2 for bidirectional, VREF = 0V for unidirectional, VSENSE = VRS+ - VRS= 0V, MAX9922 is set for AV =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = VDD, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 6
Typical Operating Characteristics (VDD = 3.3V, VSHDN = VDD, VRSB = VRS+ = VRS- = 12V, TA = +25°C, unless otherwise noted.) 80 70 50 60 60 MAX9922/23 toc02 60 MAX9922/23 toc01 90 50 40 40 30 N (%) 40 50 N (%) N (%) MAX9922 OFFSET VOLTAGE DRIFT HISTOGRAM MAX9922 INPUT OFFSET VOLTAGE HISTOGRAM MAX9922/23 toc03 MAX9922 UNIPOLAR GAIN ACCURACY HISTOGRAM 30 30 20 20 10 10 20 10 0 0 0 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.
PAGE 7
Ultra-Precision, High-Side Current-Sense Amplifiers SUPPLY CURRENT vs. TEMPERATURE RSB CURRENT vs. TEMPERATURE 0.9 VDD = 5.5V VDD = 3.3V 0.8 0.7 VDD = 2.85V 0.6 MAX9922/23 toc10 1.0 SUPPLY CURRENT (mA) 1.1 SUPPLY CURRENT (mA) 0.4 MAX9922/23 toc09 1.2 0.3 VRSB = 28V VRSB = 12V 0.2 VRSB = 1.9V 0.1 0.5 0.4 0 -15 10 35 60 -40 -15 35 60 TEMPERATURE (°C) SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX9922 GAIN vs.
PAGE 8
Typical Operating Characteristics (continued) (VDD = 3.3V, VSHDN = VDD, VRSB = VRS+ = VRS- = 12V, TA = +25°C, unless otherwise noted.) PEAK-TO-PEAK NOISE (0.1Hz TO 10Hz) INPUT NOISE DENSITY vs. FREQUENCY MAX9922/23 toc16 MAX9922/23 toc15 250 NOISE DENSITY (nV/√Hz) 200 150 1.25µV/div 100 50 32kHz SPIKE ENERGY = 4.
PAGE 9
Ultra-Precision, High-Side Current-Sense Amplifiers MAX9922/23 toc20 INPUT (100mV/div) MAX9922/23 toc21 OVERLOAD RECOVERY (OUTPUT LIMITING) (MAX9922, AV = 100) SATURATION/OVERLOAD RECOVERY (INPUT LIMITED) (MAX9922) INPUT (50mV/div) 0V 0V OUTPUT (1V/div) OUTPUT (1V/div) 0V 0V GAIN = 5V/V TIME (150µs/div) TIME (200µs/div) Pin Description PIN NAME FUNCTION 1 RSB 2 RS+ Current-Sense Amplifier Positive Input 3 RS- Current-Sense Amplifier Negative Input 4 N.C. No Connection.
PAGE 10
Ultra-Precision, High-Side Current-Sense Amplifiers MAX9922/MAX9923 Functional Diagrams RSB RS+ 1 10 2 9 3 8 4 7 VDD RSB OUT RS+ 1 10 2 9 R2 RS- FB GND 5 MAX9922 GAIN = 1 + 6 REF SHDN RS- 8 N.C. GND 7 MAX9923 5 R2 The MAX9922/MAX9923 monitor current through a current-sense resistor and amplify the voltage across the resistor. The 28V input common-mode voltage (VRS+) range of the MAX9922/MAX9923 is independent of the supply voltage (V DD ).
PAGE 11
Ultra-Precision, High-Side Current-Sense Amplifiers 5V VOUT - VREF AV = 100 2.5V CHARGE CURRENT -25mV 0 25mV DISCHARGE CURRENT -2.5V ( VOUT = RSENSE x 1 + R2 x ISENSE + VREF R1 ) Figure 1. Bidirectional Current-Sense Transfer Function Shutdown The MAX9922/MAX9923 feature a logic shutdown input to reduce the supply current to less than 1µA. Drive SHDN high for normal operation. Drive SHDN low to place the device in shutdown mode.
PAGE 12
MAX9922/MAX9923 Ultra-Precision, High-Side Current-Sense Amplifiers Optional Noise Reduction Capacitor Sense Resistor Connections A noise reduction capacitance of ~1nF can be connected between OUT and FB, if needed. Noise reduction is achieved by both limiting the amplifier bandwidth, reducing contribution of broadband white noise and by attenuating contribution of any small 20kHz autozero ripple that appears at the output.
PAGE 13
Ultra-Precision, High-Side Current-Sense Amplifiers Unidirectional Mode VSENSE BATT 1.9V TO 28V 3.3V RSB RS+ RLOAD RS- VDD 12-BIT ADC OUT MAX9923T MAX9923H MAX9923F ON SHDN 1nF* FB REF GND OFF *OPTIONAL NOISE REDUCTION Bidirectional Mode VSENSE TO WALL-CUBE/CHARGER BATT 1.9V TO 28V 3.3V RSB RS+ RLOAD RS- VDD 12-BIT ADC VREF = 2.5V OUT ON MAX9923T MAX9923H MAX9923F SHDN GND 1nF* FB REF 1.
PAGE 14
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. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 10 µMAX U10-2 21-0061 10LUMAX.
PAGE 15
Ultra-Precision, High-Side Current-Sense Amplifiers REVISION NUMBER REVISION DATE 0 3/09 Initial release 1 1/10 Updated conditions for REF input current and Note 6 DESCRIPTION PAGES CHANGED — 3, 5 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.