Datasheet

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General Description

The MAX9938 high-side current-sense amplifier offers

precision accuracy specifications of V

less than

500μV (max) and gain error less than 0.5% (max).

Quiescent supply current is an ultra-low 1μA. The

MAX9938 fits in a tiny, 1mm x 1mm UCSP™ package

size or a 5-pin SOT23 package, making the part ideal for

applications in notebook computers, cell phones, PDAs,

and all battery-operated portable devices where accura-

cy, low quiescent current, and small size are critical.

The MAX9938 features an input common-mode voltage

range from 1.6V to 28V. These current-sense amplifiers

have a voltage output and are offered in four gain versions:

25V/V (MAX9938T), 50V/V (MAX9938F), 100V/V

(MAX9938H), and 200V/V (MAX9938W).

The four gain selections offer flexibility in the choice of

the external current-sense resistor. The very low 500μV

(max) input offset voltage allows small 25mV to 50mV

full-scale V

SENSE

voltage for very low voltage drop at

full-current measurement.

The MAX9938 is offered in tiny 4-bump, UCSP (1mm x

1mm x 0.6mm footprint), 5-pin SOT23, and 6-pin μDFN

(2mm x 2mm x 0.8mm) packages specified for operation

over the -40°C to +85°C extended temperature range.

Applications

Cell Phones

PDAs

Power Management Systems

Portable/Battery-Powered Systems

Notebook Computers

Features

o Ultra-Low Supply Current of 1µA (max)

o Low 500µV (max) Input Offset Voltage

o Low < 0.5% (max) Gain Error

o Input Common Mode: +1.6V to +28V

o Voltage Output

o Four Gain Versions Available

25V/V (MAX9938T)

50V/V (MAX9938F)

100V/V (MAX9938H)

200V/V (MAX9938W)

o Tiny 1mm x 1mm x 0.6mm, 4-Bump UCSP,

5-Pin SOT23, or 2mm x 2mm x 0.8mm, 6-Pin

µDFN Packages

MAX9938

1µA, 4-Bump UCSP/SOT23,

Precision Current-Sense Amplifier

________________________________________________________________

Maxim Integrated Products

MAX9938T/F/H/W

132

RS+ RS-

GND OUTGND

SOT23

UCSP

TOP VIEW

(BUMPS ON BOTTOM)

B1 B2

GND

RS+

OUT

RS-A2

RS-

N.C.

RS+

MAX9938FELT

μDFN

TOP VIEW

(PADS ON BOTTOM)

OUT

N.C.

GND

DRAWINGS NOT TO SCALE

Pin Configurations

19-4110; Rev 6; 1/11

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.

EVALUATION KIT

AVAILABLE

UCSP is a trademark of Maxim Integrated Products, Inc.

Ordering Information

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

G45 indicates protective die coating.

Note: All devices are specified over the -40°C to +85°C

extended temperature range.

PART

PIN-

PACKAGE

GAIN

(V/V)

TOP

MARK

MAX9938TEBS+G45 4 UCSP 25 +AGD

MAX9938FEBS+G45 4 UCSP 50 +AGE

MAX9938HEBS+G45

4 UCSP 100 +AGF

MAX9938WEBS+G45

4 UCSP 200 +AGI

MAX9938TEUK+ 5 SOT23 25 +AFFB

MAX9938FEUK+ 5 SOT23 50 +AFFC

MAX9938HEUK+ 5 SOT23 100 +AFFD

MAX9938WEUK+ 5 SOT23 200 +AFGZ

MAX9938FELT+ 6 μDFN 50 +ACM

Summary of content (14 pages)

PAGE 1
9-4110; Rev 6; 1/11 KIT ATION EVALU E L B AVAILA 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Features o Ultra-Low Supply Current of 1µA (max) o Low 500µV (max) Input Offset Voltage o Low < 0.5% (max) Gain Error The MAX9938 high-side current-sense amplifier offers precision accuracy specifications of V OS less than 500μV (max) and gain error less than 0.5% (max). Quiescent supply current is an ultra-low 1μA.
PAGE 2
MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ABSOLUTE MAXIMUM RATINGS RS+, RS- to GND....................................................-0.3V to +30V OUT to GND .............................................................-0.3V to +6V RS+ to RS- ...........................................................................±30V Short-Circuit Duration: OUT to GND ..........................Continuous Continuous Input Current (Any Pin)..................................
PAGE 3
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier (VRS+ = VRS- = 3.6V, VSENSE = (VRS+ - VRS-) = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design. VOUT = 0. ICC is the total current into RS+ plus RS- pins. VOS is extrapolated from measurements for the gain-error test.
PAGE 4
Typical Operating Characteristics (continued) (VRS+ = VRS- = 3.6V, TA = +25°C, unless otherwise noted.) GAIN ERROR vs. TEMPERATURE -0.2 -0.3 -0.4 3.5 0.06 3.0 0.05 2.5 G = 100 VOUT (V) -0.1 4.0 MAX9938 toc08 0.07 GAIN ERROR (%) 0 0.04 1.5 0.02 1.0 0.01 0.5 0 -0.5 5 10 15 20 25 -15 10 35 60 85 0 50 TEMPERATURE (°C) VSENSE (mV) VOUT vs. VSENSE (SUPPLY = 1.6V) SMALL SIGNAL GAIN vs. FREQUENCY CMRR vs. FREQUENCY 1.4 AV = 25V/V 0 GAIN (dB) G = 100 1.0 G = 50 0.
PAGE 5
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier SMALL-SIGNAL PULSE RESPONSE (GAIN = 25) LARGE-SIGNAL PULSE RESPONSE (GAIN = 100) MAX9938 toc13c MAX9938 toc14a 30mV 60mV VSENSE VSENSE 10mV 40mV 1.5V 3V VOUT VOUT 1V 1V 25μs/div 20μs/div LARGE-SIGNAL PULSE RESPONSE (GAIN = 50) LARGE-SIGNAL PULSE RESPONSE (GAIN = 25) MAX9938 toc14c MAX9938 toc14b 120mV 60mV VSENSE VSENSE 10mV 20mV 3V 3V VOUT VOUT 0.5V 0.
PAGE 6
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier MAX9938 Typical Operating Circuit ILOAD RSENSE VBATT = 1.6V TO 28V RS+ R1 RSR1 VDD = 3.3V LOAD μC P MAX9938 ROUT OUT ADC 10kΩ GND Detailed Description same value as R1 to minimize offset voltage. The current through R1 is sourced by a high-voltage p-channel FET. Its source current is the same as its drain current, which flows through a second gain resistor, ROUT.
PAGE 7
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Choosing the Sense Resistor Choose RSENSE based on the following criteria: Voltage Loss A high RSENSE value causes the power-source voltage to drop due to IR loss. For minimal voltage loss, use the lowest RSENSE value. OUT Swing vs. VRS+ and VSENSE The MAX9938 is unique since the supply voltage is the input common-mode voltage (the average voltage at RS+ and RS-). There is no separate VCC supply voltage pin.
PAGE 8
MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier The MAX9938 allows two methods of filtering to help improve performance in the presence of input commonmode voltage and input differential voltage transients. Figure 1 shows a differential input filter. The capacitor CIN between RS+ and RS- along with the resistor RIN between the sense resistor and RS- helps filter against input differential voltages and prevents them from reaching the MAX9938.
PAGE 9
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ILOAD For the latest application details on UCSP construction, dimensions, tape carrier information, PCB techniques, bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, refer to the Application Note 1891: Wafer-Level Packaging (WLP) and Its Applications available on Maxim’s website at www.maximic.com/ucsp. RSENSE TO WALL-CUBE/ CHARGER VBATT = 1.
PAGE 10
MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier 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. 10 LAND PATTERN NO. PACKAGE TYPE PACKAGE CODE OUTLINE NO.
PAGE 11
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier SOT-23 5L .EPS ______________________________________________________________________________________ 11 MAX9938 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 12
MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier 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 13
1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ______________________________________________________________________________________ 13 MAX9938 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
MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 4/08 Initial release 1 9/08 Added μDFN package information 2 2/09 Added G45 designation to part number 3 10/09 Added Input Filters section and MAX9938W to the data sheet 4 2/10 Updated EC table and Input Filters section 5 8/10 Removed Power-Up Time parameter 2 6 1/11 Corrected error on Figure 2 8 DESCRIPTION — 1, 2, 4, 5, 9 1 1, 2, 6–9 2, 8 Maxim canno