MAX9928FAUA+T - Maxim

General Description

The MAX9928/MAX9929 low-cost, uni-/bidirectional,

high-side, current-sense amplifiers are ideal for moni-

toring battery charge and discharge currents in note-

books, cell phones, and other portable equipment.

These devices feature a wide -0.1V to +28V input com-

mon-mode voltage range, low 20µA supply current with

VOS less than 0.4mV, and a gain accuracy better than

1.0%. The input common-mode range is independent

of the supply voltage, ensuring that the current-sense

information remains accurate even when the measure-

ment rail is shorted to ground.

The MAX9928F features a current output with a transcon-

ductance ratio of 5µA/mV. An external resistor converts

the output current to a voltage, allowing adjustable gain

so that the input sense voltage can be matched to the

maximum ADC input swing. The MAX9929F has a voltage

output and integrates a 10kΩoutput resistor for a fixed

voltage gain of 50V/V.

A digital SIGN output indicates direction of current flow,

so the user can utilize the full ADC input range for mea-

suring both charging and discharging currents.

The MAX9928/MAX9929 are fully specified over the -40°C

to +125°C automotive temperature range, and available

in 6-bump UCSP™ (1mm x 1.5mm) and 8-pin µMAX®

packages. The UCSP package is bump-to-bump com-

patible with the MAX4372_EBT.

Features

oWide -0.1V to +28V Common-Mode Range,

Independent of Supply Voltage

o2.5V to 5.5V Operating Supply Voltage

o20µA Quiescent Supply Current

o0.4mV (max) Input Offset Voltage

oGain Accuracy Better than 1% (max)

oSIGN Output Indicates Current Polarity

oTransconductance and Gain Versions Available

5µA/mV (MAX9928F)

50V/V (MAX9929F)

oPin Compatible with the MAX4372 in UCSP

oAvailable in Ultra-Small, 3x2 UCSP

(1mm x 1.5mm) and 8-Pin µMAX Packages

Applications

Monitoring Charge/Discharge Currents in

Portable/Battery-Powered Systems

Notebook Computers

General-System/Board-Level Current Monitoring

Smart-Battery Packs/Chargers

Precision Current Sources

Smart Cell Phones

Super Capacitor Charge/Discharge

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-4251; Rev 3; 4/12

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

Note: All devices are specified over the -40°C to +125°C operating temperature range.

Denotes a lead-free/RoHS-compliant package.

T = Tape and reel.

PART OUTPUT TYPE GAIN PIN-PACKAGE TOP MARK

MAX9928FAUA+ Current Gm = 5µA/mV 8 µMAX —

MAX9928FABT+T Current Gm = 5µA/mV 3x2 UCSP +AAF

MAX9929FAUA+ Voltage AV = 50V/V 8 µMAX —

MAX9929FABT+T Voltage AV = 50V/V 3x2 UCSP +ADI

Pin Configurations and Typical Operating Circuit appear at

end of data sheet.

UCSP is a trademark and µMAX is a registered trademark of

Maxim Integrated Products, Inc.

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩfor MAX9928F, TA= -40°C to +125°C, unless other-

wise noted. Typical values are at TA = +25°C.) (Note 1)

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.

VCC, SIGN to GND ...................................................-0.3V to +6V

RS+, RS- to GND....................................................-0.3V to +30V

OUT to GND ...............................................-0.3V to (VCC + 0.3V)

Differential Input Voltage (VRS+ - VRS-) .............................. ±30V

OUT, SIGN Short Circuit to VCC or GND ...................Continuous

Current into Any Pin..........................................................±20mA

Continuous Power Dissipation (TA= +70°C)

6-Bump 1mm x 1.5mm UCSP

(derate 3.9mW/°C above +70°C)............................308.3mW

8-Pin µMAX (derate 4.8mW/°C above +70°C) .............388mW

Operating Temperature Range ........................-40°C to +125°C

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

Junction Temperature .....................................................+150°C

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

Soldering Temperature (reflow) .......................................+260°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

AMPLIFIER DC ELECTRICAL CHARACTERISTICS

TA = +25°C ±0.1 ±0.4

VRS+ = 3.6V TA = -40°C to +125°C ±0.8

TA = +25°C ±0.6 ±1.0

Input Offset Voltage (Note 2) VOS

VRS+ = -0.1V TA = -40°C to +125°C ±3.0

Common-Mode Input Range VCMR (Note 3) -0.1 +28 V

TA = +25°C 93 104

2V ≤ VRS+ ≤ 28V TA = -40°C to +125°C87

TA = +25°C6072

Common-Mode Rejection Ratio CMRR

-0.1V ≤ VRS+ ≤

+2V TA = -40°C to +125°C54

Full-Scale Sense Voltage (Note 2) VSENSE MAX992_F ±50 mV

Gain (Note 2) AVMAX9929F 50 V/V

TA = +25°C ±0.3 ±1.0

MAX9929F,

VRS+ = 3.6V TA = -40°C to +125°C ±2.5

TA = +25°C ±0.3 ±1.0

Gain Accuracy (Notes 2, 6)

MAX9929F,

VRS+ = -0.1V TA = -40°C to +125°C ±2.8

Transconductance (Note 2) GMMAX9928F 5 µA/mV

TA = +25°C ±0.3 ±1.0

MAX9928F,

VRS+ = 3.6V TA = -40°C to +125°C ±2.5

TA = +25°C ±0.3 ±1.0

Transconductance Accuracy

(Note 2) MAX9928F,

VRS+ = -0.1V TA = -40°C to +125°C ±2.8

2V ≤ VRS+ ≤ 28V 0 1.6 6

Input Bias Current (Note 4) IRS+, IRS- -0.1V ≤ VRS+ ≤ +2V -80 +6 µA

2V ≤ VRS+ ≤ 28V ±0.05 ±1

Input Offset Bias Current (Note 4) IOS -0.1V ≤ VRS+ ≤ +2V ±0.2 ±2 µA

Input Leakage Current IRS+, IRS- VCC = 0V, VRS+ = VRS- = 28V (Note 5) 0.05 1.0 µA

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩfor MAX9928F, TA= -40°C to +125°C, unless other-

wise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MAX9928F 5 MΩ

Output Resistance R

OUT

MAX9929F 6.4 10 13.6 kΩ

MAX9928F, R

OUT

= 10kΩ(V

0.1)

0.45)

Output High Voltage (Note 6) V

MAX9929F (V

0.1)

0.45)

= +25°C 0.25 2.0

Minimum Output Voltage (Note 7) V

MAX9929F T

= -40°C to +125°C15

= +25°C 0.025 0.2

Minimum Output Current (Note 7) I

MAX9928F T

= -40°C to +125°C 1.5 µA

SIGN COMPARATOR DC ELECTRICAL CHARACTERISTICS

= +25°C -1.6 -1.2 -0.5

RS+

= 3.6V T

= -40°C to +125°C -2.15 -0.15

= +25°C -2.5 -1.2 +0.25

Discharge to Charge Trip Point

(Note 8) V

TDC

RS+

= -0.1V T

= -40°C to +125°C -4.6 +2.3

RS+

= 3.6V T

= +25°C-1.8

Charge to Discharge Trip Point

(Note 8) V

TCD

RS+

= -0.1V T

= +25°C-1.8

Hysteresis Width V

HYS

RS+

= 3.6V,

-0.1V T

= +25°C0.6mV

Common-Mode Input Range

(Note 9) V

CMR

-0.1 +28 V

2V ≤ V

RS+

≤ 28V 102

Common-Mode Rejection Ratio

(Note 9) CMRR -0.1V ≤ V

RS+

≤ +2V 74 dB

Output Low Voltage V

SINK

= 100µA 0.03 0.1 V

Output High Voltage V

0.01)

0.04) V

Internal Pullup Resistor R

PULL-UP

1MΩ

POWER SUPPLY

= +25°C 2.5 5.5

Supply Voltage Range (Note 10) V

= -40°C to +125°C 2.8 5.5 V

RS+

= 3.6V 72 90

Amplifier Power-Supply Rejection

Ratio (Note 10) PSRR

RS+

= -0.1V 66 86 dB

RS+

= 3.6V 90

Comparator Power-Supply

Rejection Ratio PSRR

RS+

= -0.1V 86 dB

2V ≤ V

RS+

≤ 28V 20 30

Quiescent Supply Current I

-0.1V ≤ V

RS+

< +2V 115 200 µA

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩfor MAX9928F, TA= -40°C to +125°C, unless other-

wise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

AC ELECTRICAL CHARACTERISTICS

-3dB Bandwidth BW MAX992_F, VSENSE = 50mV 150 kHz

MAX992_F, VSENSE =

5mV to 50mV step 6

OUT Settling to 1% of Final Value tSET

VRS+ = 3.6V,

CLOAD = 10pF,

ROUT = 10kΩ for

MAX9928F

MAX992_F, VSENSE =

50mV to 5mV step 15

µs

Overdrive = 1mV 80

SIGN Comparator Propagation

Delay (Low to High) tPROP_LH Overdrive = 5mV 30 µs

Overdrive = 1mV 50

SIGN Comparator Propagation

Delay (High to Low) tPROP_HL Overdrive = 5mV 13 µs

Power-Up Time to 1% of Final

Value

VSENSE = 50mV for MAX992_F,

VRS+ = 3.6V, CLOAD = 10pF 50 µs

Saturation Recovery Time 100mV ≤ VSENSE ≤ 50mV for MAX992_F,

VRS+ = 3.6V, CLOAD = 10pF 4ms

Note 1: All devices are 100% production tested at TA= +25°C. All temperature limits are guaranteed by design.

Note 2: VOS is extrapolated from two point transconductance and gain accuracy tests. Measurements are made at VSENSE =

+5mV and VSENSE = +50mV for MAX992_F. These measurements are also used to test the full-scale sense voltage,

transconductance, and gain. These VOS specifications are for the trimmed direction only (VRS+ > VRS-). For current flowing

in the opposite direction (VRS- > VRS+), VOS is ±1mV (max) at +25°C and ±1.8mV (max) over temperature, when VRS+ is at

3.6V. See the

Detailed Description

for more information.

Note 3: Guaranteed by common-mode rejection ratio. Extrapolated VOS as described in Note 2 is used to calculate common-mode

rejection ratio.

Note 4: Includes input bias current of SIGN comparator.

Note 5: Leakage in to RS+ or RS- when VCC = 0V. Includes input leakage current of SIGN comparator. This specification does not

add to the bias current.

Note 6: Output voltage should be 650mV below VCC to achieve full accuracy.

Note 7: IOL is the minimum output current in the VSENSE - IOUT transfer characteristics. VOL is the minimum output voltage in the

VSENSE - VOUT transfer characteristic.

Note 8: VSENSE voltage required to switch comparator.

Note 9: Discharge to charge trip point is functionally tested at VCM = -0.1V, +3.6V, and +28V.

Note 10: Guaranteed by PSRR test. Extrapolated VOS as described in Note 2 is used to calculate the power-supply rejection ratio.

VSENSE has to be such that the output voltage is 650mV below VCC to achieve full accuracy.

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

_______________________________________________________________________________________

VOS HISTOGRAM

MAX9928 toc01

VOS (mV)

FREQUENCY (%)

0.30

0.200.10

-0.20 -0.10 0

-0.30

-0.40 0.40

AV = 50V/V

GAIN ACCURACY

HISTOGRAM

MAX9928 toc02

GAIN ACCURACY (%)

FREQUENCY (%)

0.8

0.6

0.4

-0.6 -0.4 0.2

-0.2 0

-0.8

-1.0 1.0

AV = 50V/V

OFFSET VOLTAGE

vs. COMMON-MODE VOLTAGE

MAX9928 toc03

COMMON-MODE VOLTAGE (V)

OFFSET VOLTAGE (mV)

320 1

-1.5

-1.0

-0.5

1.0

0.5

1.5

2.0

-2.0

-1 28

OFFSET VOLTAGE vs. TEMPERATURE

MAX9928 toc04

TEMPERATURE (°C)

OFFSET VOLTAGE (mV)

1109565 80-10 520 35 50-25

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0

-40 125

VCM = 3.6V

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9928 toc05

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (μA)

5.04.54.03.53.0

100

125

150

2.5 5.5

VRS+ = 0V

VSENSE = 0V

VRS+ = 3.6V

SUPPLY CURRENT

vs. COMMON-MODE VOLTAGE

MAX9928 toc06

COMMON-MODE VOLTAGE (V)

SUPPLY CURRENT (μA)

2.01.51.00.50

150

120

-0.5 28

VCC = 5.5V

VCC = 2.5V

SUPPLY CURRENT

vs. TEMPERATURE

MAX9928 toc07

TEMPERATURE (°C)

SUPPLY CURRENT (μA)

7550250-25

100

125

150

-50 125100

VRS+ = 0V

VSENSE = 0V

VRS+ = 3.6V

-80

-60

-70

-30

-40

-50

-10

-20

-2 2 406810

INPUT BIAS CURRENT

vs. COMMON-MODE VOLTAGE

MAX9928 toc08

COMMON-MODE VOLTAGE (V)

INPUT BIAS CURRENT (μA)

-0.1

Typical Operating Characteristics

(VCC = 3.3V, VRS+ = 12V, TA= +25°C, unless otherwise noted.)

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

6 _______________________________________________________________________________________

MAX9928F

IOUT vs. VSENSE

MAX9928 toc09

VSENSE (V)

IOUT (μA)

0.40.30.20.1

500

1000

1500

2000

2500

00.5

TA = -40°C

TA = +125°C

VOUT = 0V

TA = +25°C

MAX9929F

VOUT vs. VSENSE

MAX9928 toc10

VSENSE (mV)

VOUT (V)

12010080604020

0 140

VCC = 5.5V

VCC = 3.3V

VCC = 2.7V

VCC = 2.5V

MAX9929F

VOUT vs. VSENSE

MAX9928 toc11

VSENSE (mV)

VOUT (V)

8070605040

2.2

2.4

2.6

2.8

3.0

3.2

3.4

2.0

30 90

TA = -40°C

TA = +125°C

TA = +25°C

GAIN ACCURACY

vs. SUPPLY VOLTAGE

MAX9928 toc12

SUPPLY VOLTAGE (V)

GAIN ACCURANCY (%)

5.04.54.03.53.0

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0

2.5 5.5

MINIMUM OUTPUT VOLTAGE

vs. TEMPERATURE

MAX9928 toc13

TEMPERATURE (°C)

MINIMUM OUTPUT VOLTAGE (mV)

1109565 80-10 5 20 35 50-25

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

-40 125

GAIN ACCURACY vs. TEMPERATURE

MAX9928 toc14

TEMPERATURE (°C)

GAIN ACCURACY (%)

1109565 80-10 520 35 50-25

-0.8

-0.6

-0.4

-0.2

0.2

0.4

0.6

0.8

1.0

-1.0

-40 125

SMALL-SIGNAL GAIN

vs. FREQUENCY

MAX9928 toc15

FREQUENCY (kHz)

GAIN (dB)

1001010.1

0.01 1000

VCM = 3.6V

MAX992_F

CMRR vs. FREQUENCY

MAX9928 toc16

FREQUENCY (Hz)

CMRR (dB)

100k10k1k100

120

10 1M

Typical Operating Characteristics (continued)

(VCC = 3.3V, VRS+ = 12V, TA= +25°C, unless otherwise noted.)

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VCC = 3.3V, VRS+ = 12V, TA= +25°C, unless otherwise noted.)

PSRR vs. FREQUENCY

MAX9928 toc17

FREQUENCY (Hz)

PSRR (dB)

10k1k100101

-100

-80

-60

-40

-20

-120

0.1 100k

MAX9929F LARGE-SIGNAL

TRANSIENT RESPONSE

MAX9928 toc18

100μs/div

VOUT

VSENSE

1V/div

50mV/div

VSIGN AND VOUT

vs. VSENSE

MAX9928 toc19

VSENSE (mV)

VOUT (mV) VSIGN (V)

21-2 -1 0

100

150

-3 3

OVERDRIVE RECOVERY

MAX9928 toc20

400μs/div

VSENSE

100mV/div

VOUT

500mV/div

COMPARATOR PROPAGATION DELAY

(RS+ = 3.6V, 5mV OVERDRIVE)

MAX9928 toc21

40μs/div

VSENSE

2mV/div

VOUT

1V/div

POWER-UP DELAY

MAX9928 toc22

40μs/div

VCC

1V/div

VOUT

1V/div

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

8 _______________________________________________________________________________________

Detailed Description

The MAX9928F/MAX9929F micropower uni-/bidirectional,

current-sense amplifiers feature -0.1V to +28V input

common-mode range that is independent of the supply

voltage. This wide input voltage range feature allows the

monitoring of the current flow out of a power supply dur-

ing short-circuit/fault conditions, and also enables high-

side current sensing at voltages far in excess of the

supply voltage (VCC). The MAX9928F/MAX9929F oper-

ate from a 2.5V to 5.5V single supply and draw a low

20µA quiescent supply current.

Current flows through the sense resistor, generating a

sense voltage VSENSE (Figure 1). The comparator sens-

es the direction of the sense voltage and configures the

amplifier for either positive or negative sense voltages

by controlling the S1 and S2 switches.

For positive VSENSE voltage, the amplifier’s inverting

input is high impedance and equals VIN - VSENSE. The

amplifier’s output drives the base of Q1, forcing its non-

inverting input terminal to (VIN - VSENSE); this causes a

current to flow through RG1 equal to |VSENSE|/RG1.

Transistor Q2 and the current mirror amplify the current

by a factor of M.

For negative VSENSE voltage, the amplifier’s noninvert-

ing input is high impedance and the voltage on RS- ter-

minal equals VIN + VSENSE. The amplifier’s output

drives the base of Q1 forcing its inverting input terminal

to match the voltage at the noninverting input terminal;

this causes a current to flow through RG2 equal to

|VSENSE|/RG2. Again, transistor Q2 and the current mir-

ror amplify the current by a factor of M.

+VSENSE vs. -VSENSE

The amplifier is configured for either positive VSENSE or

negative VSENSE by the SIGN comparator. The com-

parator has a built-in offset skew of -1.2mV so that ran-

dom offsets in the comparator do not affect the

precision of IOUT (VOUT) with positive VSENSE. The

comparator has a small amount of hysteresis (typically

0.6mV) to prevent its output from oscillating at the

crossover sense voltage. The ideal transfer characteris-

tic of IOUT (VOUT) and the output of the comparator

(SIGN) is shown in Figure 2.

The amplifier VOS is only trimmed for the positive VSENSE

voltages (VRS+ > VRS-). The SIGN comparator reconfig-

ures the internal structure of the amplifier to work with

negative VSENSE voltages (VRS- > VRS+) and the preci-

sion VOS trim is no longer effective and the resulting VOS

is slightly impacted. See details in the

Electrical

Characteristics

Note 2. The user can choose the direc-

tion that needs the best precision to be the direction

where VRS+ > VRS-. For example, when monitoring Li+

battery currents, the discharge current should be VRS+ >

VRS- to give the best accuracy over the largest dynamic

range. When the battery charger is plugged in, the

charge current flows in the opposite direction and is

usually much larger, and a higher VOS error can be

tolerated. See the

Typical Operating Circuit

For applications with unidirectional currents (e.g., bat-

tery discharge only), the SIGN output can be ignored.

Note that as VSENSE increases, the output current (IOUT

for the MAX9928 or VOUT/10kΩfor the MAX9929) also

increases. This additional current is supplied from VCC.

Pin/Bump Description

PIN BUMP

µMAX UCSP NAME FUNCTION

1 B3 RS- Negative Current-Sense Input. Load-side connection for the external sense resistor.

2 B2 SIGN

SIGN Output. Indicates polarity of VSENSE.

SIGN = H indicates VRS+ > VRS-

SIGN = L indicates VRS+ < VRS-

3 B1 RS+ Positive Current-Sense Input. Power-side connection to the external sense resistor.

4, 5 — N.C. No Connection. Not internally connected.

6A1V

CC Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.

7 A2 GND Circuit Ground

8 A3 OUT Current-Sense Output. MAX9928: Current output (IOUT is proportional to |VSENSE|). MAX9929:

Voltage output (VOUT is proportional to |VSENSE|).

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

_______________________________________________________________________________________ 9

For both positive and negative VSENSE voltages, the

current flowing out of the current mirror is equal to:

IOUT = M x |VSENSE|/RG1

For the MAX9928F, the transconductance of the device

is trimmed so that IOUT/|VSENSE| = 5µA/mV. For the

MAX9929F, the voltage gain of the device is trimmed

so that VOUT/|VSENSE| = 50V/V. The SIGN output from

the comparator indicates the polarity of VSENSE.

Current Output (MAX9928F)

The output voltage equation for the MAX9928_ is given

below:

VOUT = (RSENSE x ILOAD) x (Gm X ROUT)

where VOUT = the desired full-scale output voltage,

ILOAD = the full-scale current being sensed, RSENSE =

the current-sense resistor, ROUT = the voltage-setting

resistor, and Gm= MAX9928F transconductance

(5µA/mV).

The full-scale output voltage range can be set by

changing the ROUT resistor value. The above equation

can be modified to determine the ROUT required for a

particular full-scale range:

ROUT = (VOUT)/(ILOAD x RSENSE x Gm)

OUT is a high-impedance current source and can drive

an unlimited amount of capacitance.

CURRENT

MIRROR

MAX9928F

MAX9929F

Q2 10kΩ*

SIGN

OUT

VCC

VIN

-0.1V TO +28V

(VBATT)

SENSE

2.5V TO 5.5V

RG1

80kΩ

RG2

80kΩ

RC2

80kΩ

RC1

80kΩ

RS-

RS+

LOAD/CHARGER

TO ADC

TO μC

*INTERNAL 10kΩ RESISTOR FOR MAX9929_ ONLY.

GND

VCC

1MΩ

Figure 1. Functional Diagram

0-1.2-1.8-3.0 3.02.01.0

VSENSE (mV)

SIGN

OUT

)

( ) FOR THE MAX9929F.

Figure 2. Ideal Transfer Characteristics with 0mV Amplifier Input

Offset Voltage and -1mV Comparator Input Offset Voltage

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

10 ______________________________________________________________________________________

Voltage Output (MAX9929F)

The output voltage equation for the MAX9929_ is given

below:

VOUT = (RSENSE x ILOAD) x (AV)

where VOUT = the desired full-scale output voltage,

ILOAD = the full-scale current being sensed, RSENSE =

the current-sense resistor, AV= MAX9929F voltage

gain (50V/V).

SIGN Output

The current/voltage at OUT indicates magnitude. The

SIGN output indicates the current’s direction. The SIGN

comparator compares RS+ to RS-. The sign output is

high when RS+ is greater than RS- indicating positive

current flow. The sign output is low when RS- is greater

than RS+ indicating negative current flow. In battery-

operated systems, this is useful for determining

whether the battery is charging or discharging. The

SIGN output might not correctly indicate the direction of

load current when VSENSE is between -1.8mV to -1.2mV

(see Figure 2). Comparator hysteresis of 0.6mV pre-

vents oscillation of SIGN output. If current direction is

not needed, leave SIGN unconnected.

Applications Information

Choosing RSENSE

The MAX9928F/MAX9929F operate over a wide variety

of current ranges with different sense resistors. Adjust

the RSENSE value to monitor higher or lower current lev-

els. Select RSENSE using these guidelines:

•Voltage Loss: A high RSENSE value causes the

power-source voltage to drop due to IR loss. For

least voltage loss, use the lowest RSENSE value.

•Accuracy: A high RSENSE value allows lower cur-

rents to be measured more accurately. This is

because offsets become less significant when the

sense voltage is larger.

•Efficiency and Power Dissipation: At high current

levels, the I2R losses in RSENSE might be significant.

Take this into consideration when choosing the resis-

tor value and power dissipation (wattage) rating.

Also, if the sense resistor is allowed to heat up exces-

sively, its value could drift.

•Inductance: If there is a large high-frequency com-

ponent to ISENSE, keep inductance low. Wire-wound

resistors have the highest inductance, while metal

film is somewhat better. Low-inductance metal-film

resistors are available. Instead of being spiral

wrapped around a core, as in metal film or wire-

wound resistors, these are a straight band of metal.

They are made in values under 1Ω.

Use in Systems with Super Capacitors

Since the input common-mode voltage range of the

MAX9928/MAX9929 extends all the way from -0.1V to

28V, they are ideal to use in applications that require

use of super capacitors for temporary or emergency

energy storage systems. Some modern industrial and

automotive systems use multifarad (1F–50F) capacitor

banks to supply enough energy to keep critical sys-

tems alive even if the primary power source is removed

or temporarily disabled. Unlike batteries, these capaci-

tors can discharge all the way down to 0V. The

MAX9928/MAX9929 can continuously help monitor their

health and state of charge/discharge.

UCSP Applications Information

For the latest application details on UCSP construction,

dimensions, tape carrier information, PCB techniques,

bump-pad layout, and recommended reflow tempera-

ture profile, as well as the latest information on reliability

testing results, go to Maxim’s website at www.maxim-

ic.com/ucsp to find Application Note 1891:

Understanding the Basics of the Wafer-Level Chip-

Scale Package (WL-CSP).

Chip Information

PROCESS: BiCMOS

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

______________________________________________________________________________________ 11

OUT

GND

VCC

N.C.N.C.

RS+

SIGN

RS-

MAX9928F

MAX9929F

μMAX

TOP VIEW

UCSP

(1mm x 1.5mm)

TOP VIEW

(BUMPS ON THE BOTTOM)

VCC GND OUT

RS+ SIGN RS-

MAX9928F

MAX9929F

Pin Configurations

μC

DIGITAL

INPUT

ADC

GND

RSENSE

2.5V TO

5.5V

0.1μF

VIN

-0.1V TO

+28V

OUT

SIGN

VCC

RS+ RS-

ROUT*

*FOR THE MAX9928F ONLY

MAX9928F

MAX9929F

LOAD

WALL-CUBE

CHARGER

Typical Operating Circuit

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

12 ______________________________________________________________________________________

Package Information

For the latest package outline information and land patterns (footprints), 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 per-

tains to the package regardless of RoHS status.

PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.

8 µMAX U8+1 21-0036

90-0092

6 UCSP B6+1 21-0097

—

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

______________________________________________________________________________________ 13

Package Information (continued)

For the latest package outline information and land patterns (footprints), 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 per-

tains to the package regardless of RoHS status.

MAX9928/MAX9929

-0.1V to +28V Input Range, Micropower,

Uni-/Bidirectional, Current-Sense Amplifiers

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. The parametric values (min and max limits) shown in

the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 12/08 Initial release —

1 8/09 Removed MAX9928T and MAX9929T from data sheet 1–5, 7–12

2 4/11 Updated top marks 1

3 4/12 Removed the R61A1+1 package code note and references 1