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19-2423; Rev 2; 1/03
Bidirectional, High-Side, Current-Sense Amplifiers with Reference
General Description
The MAX4069-MAX4072 low-cost, bidirectional, highside, current-sense amplifiers are ideal for monitoring battery charge and discharge currents in notebooks, cell phones, and other portable equipment. They feature up to 24V input common-mode voltage range, low 100A supply current (which drops to only 10A in shutdown), and a total output error of less than 1.5%. The wide 1.35V to 24V input common-mode range is independent of the supply voltage, ensuring that the current-sense feedback remains accurate even when connected to a battery pack in deep discharge. To achieve maximum flexibility, an external current-sense resistor is used along with a Gain Select pin to choose either 50V/V or 100V/V. A single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX4070 contains an internal 2.5V reference. The charging current is represented by an output voltage from 2.5V to VCC, while discharge current is given from 2.5V to GND. The MAX4071 is similar, but with a reference voltage of 1.5V. The MAX4069 has an adjustable reference voltage, set by two external resistors. The MAX4072 has an input for an external reference. The MAX4069/MAX4071/MAX4072 operate from a 2.7V to 24V single supply. The MAX4070 operates from a 3.6V to 24V single supply. All devices are specified over the automotive operating temperature range, -40C to +125C. The MAX4070/MAX4071/MAX4072 are available in 8-pin MAX and 8-pin thin QFN packages. The MAX4069 is available in a 10-pin MAX package. o Total Output Error Less than 1.5% o Selectable Gain of 50V/V or 100V/V o Wide 1.35V to 24V Common-Mode Range Independent of Supply Voltage o 2.7V to 24V Single-Supply Operation o Internal Precision Reference Adjustable (MAX4069) 2.50V (MAX4070) 1.50V (MAX4071) o Low 100A Supply Current o 10A Supply Current in Shutdown o Available in Space-Saving Packages 8-Pin Thin QFN (MAX4070/MAX4071/MAX4072) 8-Pin MAX (MAX4070/MAX4071MAX4072) 10-Pin MAX (MAX4069)
Features
o Bidirectional, Compact, Current-Sense Solution
MAX4069-MAX4072
Ordering Information
PART MAX4069AUB MAX4070AUA MAX4070ATA MAX4071AUA MAX4071ATA MAX4072AUA MAX4072ATA TEMP RANGE PIN-PACKAGE TOP MARK -- -- ABN -- ABO -- ABP
-40C to +125C 10 MAX -40C to +125C 8 MAX -40C to +125C 8 Thin QFN-EP* -40C to +125C 8 MAX -40C to +125C 8 Thin QFN-EP* -40C to +125C 8 MAX -40C to +125C 8 Thin QFN-EP*
Applications
Notebook Fuel Gauging Smart-Battery Packs/Chargers Motor Control Power-Management Systems Cell-Phone Battery-Current Monitoring
*EP = Exposed paddle.
Typical Operating Circuit
FROM BATTERY CHARGER RSENSE VBATT = 1.35V TO 24V RSRS+
Selector Guide
PART MAX4069 MAX4070 MAX4071 MAX4072 REFERENCE ADJUSTABLE 2.5V 1.5V EXTERNAL SUPPLY VOLTAGE RANGE (V) 2.7 to 24 3.6 to 24 2.7 to 24 2.7 to 24 COMMONMODE RANGE (V) 1.35 to 24 1.35 to 24 1.35 to 24 1.35 to 24
VCC = 3.6V TO 24V VCC
LOAD
MAX4070
GSEL OUT TO ADC
SHDN GND
REFOUT
2.5V
Pin Configurations appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
ABSOLUTE MAXIMUM RATINGS
VCC, RS+, RS- to GND ...........................................-0.3V to +26V OUT to GND ....................-0.3V to Lesser of (VCC + 0.3V) or 15V Differential Input Voltage (VRS+ - VRS-) ..............................0.3V GSEL, SHDN, REFOUT, REFIN and ADJ to GND.....................................-0.3V to (VCC + 0.3V) OUT Short-Circuit Duration to GND or to Lesser of (VCC or 15V) ...................................Continuous REFOUT Short Circuit to VCC or GND........................Continuous Current into Any Pin ..........................................................20mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5 mW/C above +70C) ............362mW 8-Pin Thin QFN (derate 24.4mW/C above +70C) ...1951mW 10-Pin MAX (derate 5.6 mW/C above +70C) .......444.4mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VRS+ = VRS- = VCC = 2.7V to 24V, VSENSE = VRS+ - VRS- = 0V, IREFOUT = 0, V SHDN = VCC, VGSEL = GND, VREFIN = 2.5V (MAX4072), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C and at VCC = VRS+ = 12V.) (Notes 1, 2)
PARAMETER Operating Voltage Range (Note 3) Input-Referred Offset Voltage (Note 5) Common-Mode Input Range Common-Mode Rejection Ratio Supply Current SYMBOL VCC MAX4070 VCC = VRS+ = VRS- = 12V TA = +25C TA = -40C to +85C TA = TMIN to TMAX 1.35 100 120 100 9 A 10 0.1 0 2.4 75 50 30 0.5 5 A A mV 250 CONDITIONS MAX4069/MAX4071/MAX4072 (Note 4) MIN 2.7 3.6 0.08 TYP MAX 24 24 0.25 0.8 1 24 V dB A mV UNITS V
VOS CMVR CMRR ICC
Guaranteed by CMRR test 1.35V VRS+ = VRS- 24V, VCC = 12V VCC = VRS+ = VRS- = 24V, RL = open, TA = TMIN to TMAX VCC = VRS+ = VRS- = 5.5V, SHDN = GND, TA = +25C VCC = VRS+ = VRS- = 24V, SHDN = GND VRS+ = VRS- = 24V, VCC = 0V VCC = VRS+ = VRS- = 24V Gain = 50V/V Gain = 100V/V
Shutdown Supply Current
ICC SHDN
Leakage Current Input Bias Current Recommended Full-Scale Sense Voltage (Note 6) IRS+, IRSVSENSE
2
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = VRS- = VCC = 2.7V to 24V, VSENSE = VRS+ - VRS- = 0V, IREFOUT = 0, V SHDN = VCC, VGSEL = GND, VREFIN = 2.5V (MAX4072), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C and at VCC = VRS+ = 12V.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS VSENSE = 75mV, VCC = VRS+ = 12V, gain = 50 VSENSE = 50mV, VCC = VRS+ = 12V, gain = 100 MAX4069/MAX4070/ MAX4072: VSENSE = -35mV, VCC = VRS+ = 12V, gain = 50 MAX4069/MAX4070/ MAX4072: VSENSE = -17.5mV, VCC = VRS+ = 12V, gain = 100 MAX4071: VSENSE = -15mV, VCC = VRS+ = 12V, gain = 50 MAX4071: VSENSE = -7.5mV, VCC = VRS+ = 12V, gain = 100 VSENSE = 3mV, VCC = 12V, VRS+ = 12V TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C TA = -40C to +85C TA = TMIN to TMAX TA = +25C 3 2.0 1.0 0.8 0.4 0.25 MIN TYP 0.25 MAX 1.0 1.5 2.0 1.0 1.5 2.5 1.0 2.0 3.0 2.0 4.0 6 2.5 4.0 6.0 5 10 15 % UNITS
MAX4069-MAX4072
Total OUT Voltage Error (Note 7)
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = VRS- = VCC = 2.7V to 24V, VSENSE = VRS+ - VRS- = 0V, IREFOUT = 0, V SHDN = VCC, VGSEL = GND, VREFIN = 2.5V (MAX4072), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C and at VCC = VRS+ = 12V.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MAX4071, VCC = 2.7V MAX4069/MAX4070/ MAX4072, VCC = 3.6V MAX4071, VCC = 2.7V MAX4069/MAX4070/ MAX4072, VCC = 3.6V MAX4071, VCC = 2.7V MAX4069/MAX4070/ MAX4072, VCC = 3.6V MAX4071, VCC = 2.7V MAX4069/MAX4070/ MAX4072, VCC = 3.6V MIN TYP 65 MAX 150 UNITS
IOUT = 10A, VSENSE = 100mV, VRS+ = VCC OUT Voltage High VCC - VOH IOUT = 500A, VSENSE = 100mV, VRS+ = VCC
65
150 mV
90
250
90
250
5
20
IOUT = -10A, VSENSE = -100mV, VRS+ = VCC OUT Voltage Low VOL IOUT = -500A, VSENSE = -100mV, VRS+ = VCC
5
20 mV
100
250
100 100 40 50 100 100
250
-3dB Bandwidth Gain Capacitive-Load Stability Power-Supply Rejection Ratio Logic Low Voltage (GSEL, SHDN) Logic High Voltage (GSEL, SHDN) Gain-Select Input Current Shutdown Input Current
BW AV
Gain = 50V/V VSENSE = 50mV, VCC = 12V, CL = 100pF Gain = 100V/V GSEL = GND GSEL = VCC VCC = 2.7V to 24V (MAX4069/MAX4071/MAX4072), VCC = 3.6V to 24V (MAX4070) VCC = 3.6V or 24V VCC = 3.6V or 24V GSEL = VCC = 24V or GND SHDN = VCC = 24V SHDN = GND, VCC = 24V 2
kHz V/V pF dB 0.6 V V A A
PSRR VIL VIH IGSEL ISHDN
100
120
0.01 3 0.01
1 12 1
4
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = VRS- = VCC = 2.7V to 24V, VSENSE = VRS+ - VRS- = 0V, IREFOUT = 0, V SHDN = VCC, VGSEL = GND, VREFIN = 2.5V (MAX4072), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C and at VCC = VRS+ = 12V.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4069-MAX4072
REFOUT (MAX4069/MAX4070/MAX4071) MAX4069, VCC = 12V (Note 2) Reference Output Voltage VREF MAX4070, VCC = 12V MAX4071, VCC = 12V Reference Output Voltage Temperature Coefficient Load Regulation Line Regulation REF Capacitive-Load Stability Reference Adjust Voltage Threshold Reference Output Voltage Range Reference Adjust Input Current REFIN (MAX4072 only) Input-Voltage Range Input Current VCC = 12V REFIN = 2.5V, VCC = 12V 1 -60 4 +20 V A IADJ VADJ MAX4069, VCC = 12V MAX4069, range adjustable with R1 and R2, VCC = 12V MAX4069, VCC = 12V, VADJ = 1.23V TCVREF VREFOUT /IREF VREF/ VCC VCC = 12V TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX -40C TA +85C TA = TMIN to TMAX 2.44 2.39 2.45 2.40 1.47 1.44 15 20 2 4 20 500 1.230 VADJ to +4 100 1.5 2.5 2.49 2.54 2.59 2.55 2.60 1.53 1.56 ppm/C mV/mA V/V pF V V nA V
IREFOUT = 0 to 500A IREFOUT = 0 to -100A 2.7V VCC 24V
All devices are 100% tested at TA = +25C. Limits over temperature are guaranteed by design. R1 = 215k, R2 = 210k for the MAX4069 only (see Functional Diagram). This sets REFOUT to 2.49V nominal. Guaranteed by the PSRR test. The REFOUT voltage for the MAX4069 should be set such that it does not exceed VCC - 1.1V. Similarly, the maximum REFIN voltage for the MAX4072 should also be less than VCC - 1.1V. Note 5: Input-Referred Offset Voltage is defined as the voltage difference between OUT and REFOUT, divided by the selected gain of either 50 or 100, when VSENSE = VRS+ - VRS- = 0V. Note 6: The negative full-scale sense voltage is limited by the voltage range of OUT from VREFOUT to GND. Note 7: Total OUT Voltage Error is the sum of offset voltage and gain errors. The output voltage is measured relative to the reference (REFOUT or REFIN). Note 1: Note 2: Note 3: Note 4:
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Typical Operating Characteristics
(VCC = VRS+ = 12V, VSENSE = 50mV for gain of 100V/V and 75mV for gain of 50V/V, TA = +25C, unless otherwise noted.)
INPUT OFFSET VOLTAGE vs. TEMPERATURE
MAX4069-72 toc01 MAX4069-72 toc02
INPUT OFFSET VOLTAGE DISTRIBUTION
35 30 PERCENTAGE OF UNITS (%) 25 20 15 10 5 0 -200 -160 -120 -80 -40 0 40 80 120 160 200 150 125 100 75 50 25 0 -25 -50 -75 -100 -125 -150 -50 -25
(VOUT - VREF) vs. VSENSE
MAX4069-72 toc03
AV = 100V/V
12 11 10 9 (VOUT - VREF) (V) 8 7 6 5 4 3 2 1 0 0 AV = 100V/V
INPUT OFFSET VOLTAGE (V)
AV = 50V/V
0
25
50
75
100
125
25 50 75 100 125 150 175 200 225 250 VSENSE (V)
VOS (V)
TEMPERATURE (C)
TOTAL ERROR vs. SUPPLY VOLTAGE
MAX4069-72 toc04
TOTAL ERROR vs. SUPPLY VOLTAGE (VSENSE = 3mV)
MAX4069-72 toc05
TOTAL ERROR vs. TEMPERATURE
VSENSE = 50mV AV = 100V/V VCC = 24V
MAX4069-72 toc06
0.5 0.4 0.3 TOTAL ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 4 6 8 VSENSE = 50mV AV = 100V/V VSENSE = 75mV AV = 50V/V
2.0 1.5 1.0 TOTAL ERROR (%) 0.5 0 -0.5 -1.0 -1.5 -2.0 2 6 10 AV = 100V/V
1.5 1.0 TOTAL ERROR (%) 0.5 0 -0.5 -1.0
VCC = 12V
AV = 50V/V -1.5 14 18 22 -50 -25 0 25 50 75 100 125 SUPPLY VOLTAGE (V) TEMPERATURE (C)
10 12 14 16 18 20 22 24 SUPPLY VOLTAGE (V)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4069-72 toc07
SUPPLY CURRENT vs. TEMPERATURE
MAX4069-72 toc08
MAX4069 REFOUT vs. TEMPERATURE
1.245 1.240 1.235 REFOUT (V) REFOUT CONNECTED TO ADJ
MAX4069-72 toc09
140 AV = 100V/V 130 SUPPLY CURRENT (A) 120 110 100 MAX4069 90 80 70 60 2 4 6 MAX4072 MAX4070 MAX4071
180 AV = 50V/V 160 SUPPLY CURRENT (A) 140 120 100 80 60 40 VCC = 12V VCC = 24V
1.250
1.230 1.225 1.220 1.215 1.210 1.205 1.200
8 10 12 14 16 18 20 22 24 SUPPLY VOLTAGE (V)
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
TEMPERATURE (C)
TEMPERATURE (C)
6
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference
Typical Operating Characteristics (continued)
(VCC = VRS+ = 12V, VSENSE = 50mV for gain of 100V/V and 75mV for gain of 50V/V, TA = +25C, unless otherwise noted.)
MAX4070 REFOUT vs. TEMPERATURE
MAX4069-72 toc10
MAX4069-MAX4072
MAX4071 REFOUT vs. TEMPERATURE
MAX4069-72 toc11
MAX4069 REFOUT vs. SUPPLY VOLTAGE
1.233 1.231 1.229 REFOUT (V) 1.227 1.225 1.223 1.221 1.219 1.217 1.215
MAX4069-72 toc12
1.525 1.520 1.515 1.510 REFOUT (V) 1.505 1.500 1.495 1.490 1.485 1.480 1.475
1.235
2.540 2.525 REFOUT (V) 2.510 2.495 2.480 2.465 2.450 -50 -25 0 25 50 75 100
125
-50
-25
0
25
50
75
100
125
2
4
6
8 10 12 14 16 18 20 22 24 SUPPLY VOLTAGE (V)
TEMPERATURE (C)
TEMPERATURE (C)
MAX4070 REFOUT vs. SUPPLY VOLTAGE
MAX4069-72 toc13
MAX4071 REFOUT vs. SUPPLY VOLTAGE
MAX4069-72 toc14
VOH vs. TEMPERATURE
180 160 140 VOH (mV) 120 100 80 60 40 IL = 10A IL = 500A VOH = VCC - VOUT
MAX4069-72 toc15
2.500 2.499 2.498 2.497 REFOUT (V) 2.496 2.495 2.494 2.493 2.492 2.491 2.490 2 4 6
1.502 1.501 1.500 REFOUT (V) 1.499 1.498 1.497 1.496 1.495
200
20 0 2 6 10 14 18 22 -50 -25 0 25 50
8 10 12 14 16 18 20 22 24 SUPPLY VOLTAGE (V)
75
100
125
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
VOL vs. TEMPERATURE
MAX4069-72 toc16
SMALL-SIGNAL GAIN vs. FREQUENCY
MAX4069-72 toc17
PSRR AND CMRR vs. FREQUENCY
-20 PSRR AND CMRR (dB) -40 -60 -80 -100 -120 PSRR CMRR
MAX4069-72 toc18
250 225 200 175 VOL (mV) IL = 500A
5
0
0 AV = 50V/V
125 100 75 50 25 0 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) IL = 10A
GAIN (dB)
150
-5
-10 AV = 100V/V -15
-20 0.1 1 10 FREQUENCY (kHz) 100 1000
-140 0.01 0.1 1 FREQUENCY (Hz) 10 100
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7
Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Typical Operating Characteristics (continued)
(VCC = VRS+ = 12V, VSENSE = 50mV for gain of 100V/V and 75mV for gain of 50V/V, TA = +25C, unless otherwise noted.)
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4069-72 toc19
SMALL-SIGNAL TRANSIENT RESPONSE
MAX4069-72 toc20
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4069-72 toc21
GAIN = 50 INPUT 5mV/div
GAIN = 100 INPUT 5mV/div
GAIN = 50 INPUT 50mV/div
OUTPUT 200mV/div REF
OUTPUT 500mV/div REF
OUTPUT 2V/div REF
100s/div
100s/div
100s/div
LARGE-SIGNAL TRANSIENT RESPONSE
MAX4069-72 toc22
STARTUP DELAY
MAX4069-72 toc23
EXITING SHUTDOWN
MAX4069-72 toc24
GAIN = 100 INPUT 20mV/div VCC 10V/div VOUT 5V/div OUTPUT 2V/div REF 100s/div 20s/div 100s/div VSHDN 5V/div VOUT 2V/div
VREFOUT 5V/div
VREFOUT 2V/div
8
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference
Pin Description
PIN MAX4069 1 2 3 4 5 6 7 8 9 10 -- MAX4070/ MAX4071 1 2 3 -- 4 -- 5 6 7 8 -- MAX4072 1 2 3 -- 4 -- -- 6 7 8 5 NAME FUNCTION Shutdown Input. Drive SHDN low to select shutdown mode. Connect SHDN to VCC for normal operation. Negative Connection to the External Sense Resistor Positive Connection to the External Sense Resistor No Connection. Not internally connected. Ground. For thin QFN packages, also make an external connection from GND to the under-side exposed paddle. Adjustable Output Voltage Feedback Input. Connect a resistor-divider between REFOUT, ADJ, and GND (MAX4069 only, see Functional Diagram).
MAX4069-MAX4072
SHDN RSRS+ N.C. GND ADJ
REFOUT Reference Output Voltage (MAX4069/MAX4070/MAX4071) OUT VCC GSEL REFIN Voltage Output. The difference voltage, VOUT - VREF, is proportional to the voltage difference between RS+ and RS- and indicates the correct polarity. Supply Voltage Input. Bypass VCC to GND with a 0.1F capacitor. Gain-Setting Input. Connect GSEL low to select gain = 50V/V, or connect GSEL high to select gain = 100V/V. Reference Input Voltage (MAX4072)
Functional Diagram
2.7V TO 24V LOAD FROM BATTERY CHARGER VCC RS+ CSA RSGAIN SELECT SHUTDOWN GSEL OA SHDN VREF 1.23V REFOUT ADJ GND R2
MAX4069
OUT TO ADC
RSENSE
R1
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Detailed Description
The MAX4069-MAX4072 bidirectional, high-side, current-sense amplifiers are ideal for portable equipment. The wide 1.35V to 24V input common-mode voltage range is independent of the supply voltage, ensuring that the current-sense feedback remains accurate even when connected to a battery pack in deep discharge. The MAX4069/MAX4071/MAX4072 operate from a 2.7V to 24V single supply. Because the MAX4070 has a 2.5V internal reference, it operates from 3.6V to 24V. All devices have a low 100A supply current that reduces to only 10A (typ) in shutdown mode. To achieve maximum flexibility, an external current-sense resistor is used along with a gain select pin (GSEL) to choose either 50V/V or 100V/V. Drive GSEL low to select gain of 50V/V or drive GSEL high to choose gain of 100V/V (see Functional Diagram). The MAX4069 has an adjustable reference voltage set by two external resistors between REFOUT and ADJ, and GND pins. The MAX4070 contains an internal 2.5V reference. The MAX4071 is similar to the MAX4070 but with a fixed internal reference voltage of 1.5V. The MAX4072 has a reference input pin to allow use of external references. Charging current is represented by an output voltage from the reference voltage to VCC, while discharge current is given from the reference voltage to GND. The direction of VSENSE is totally arbitrary. The input stage of the MAX4069-MAX4072 is shown in Figure 1. Its unique topology allows for monitoring bidirectional currents through the sense resistor (RSENSE). If, for instance, current flows from RS+ to RS-, the MAX4069-MAX4072 match for the voltage drop over the external sense resistor (RSENSE) by increasing the current through the internal Q1 and RG1. At the same time, the current through Q2 and RG2 decreases, however, internal circuitry not shown in Figure 1 prevents Q2 from turning off completely. Likewise, if current flows from RSto RS+, the current through Q2 and RG2 increases and the current through Q1 decreases. In this way, the voltages at the input terminals of the internal amplifier A1 are kept constant and an accurate measurement of the sense voltage is achieved. In the following amplifier stages of the MAX4069-MAX4072, the output signal of amplifier A2 is level-shifted towards the reference voltage (VREF), resulting in a voltage at the output pin (OUT) that swings above the VREF voltage for positive-sense voltages and below VREF for negative-sense voltages.
RS+ RSENSE RS-
RG1
RG2
MAX4069-MAX4072
OUT
A1
Q1
Q2
A2
IOUT
Figure 1. Detailed Input Stage
Applications Information
Bidirectional, Current-Sense Amplifier
Systems such as laptop computers and other devices that have internal charge circuitry require a precise bidirectional, current-sense amplifier to accurately monitor the battery's current regardless of polarity. Figure 2 shows the MAX4069-MAX4072 used as a bidirectional current monitor. In Figure 2, the direction of VSENSE is assigned to charge and discharge, assuming charge is greater than discharge. The practical choice of direction is based on dynamic range at OUT, given that the range of REF to V CC is usually greater than from REF to ground. This is useful for implementing either smart battery packs or fuel gauges.
High-Current Measurement
The MAX4069-MAX4072 can achieve high-current measurements by using low-value sense resistors, which can be paralleled to further increase the currentsense limit.
Adjusting VREF (MAX4069)
The MAX4069 has an output reference voltage that can be set to a desired voltage by a two-resistor divider between REFOUT, ADJ, and GND. If REFOUT and ADJ are connected together, the minimum output reference voltage is obtained, 1.23V (typ). The maximum voltage for REFOUT is 4V (that requires VCC 5.1V). The recommended range for the external resistors is: R1 + R2 should be > 20k and < 500k.
10
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Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
ICHARGE 5V VOUT - VREF LOAD 2.5V VCC 2 CELLS GSEL CHARGE CURRENT AV = 100
IDISCHARGE
RSENSE
RS-
RS+
MAX4070
OUT TO ADC -25mV 0 25mV VSENSE SHDN GND REFOUT 2.5V DISCHARGE CURRENT 50mV
-2.5V
Figure 2. Bidirectional Current Monitor
External Reference (MAX4072)
The MAX4072 contains REFIN pin for external reference voltage. The allowable voltage range on REFIN is 1V (min) to 4V (max) with VCC 5.1V.
The MAX4069-MAX4072 sense a wide variety of currents with different sense-resistor values. Table 1 lists common resistor values for typical operation of these devices. Listed output voltage is with respect to REF.
Reference Output (MAX4069/MAX4060/MAX4071)
The REFOUT of the MAX4069/MAX4070/MAX4071 can sink 100A and source 500A. Keep the total capacitance on REFOUT under 500pF to maintain stability.
Sense Resistor, RSENSE
Choose RSENSE based on the following criteria: Voltage Loss: A high RSENSE value causes the powersource voltage to degrade through IR loss. For minimal voltage loss, use the lowest RSENSE value. Accuracy: A high RSENSE value allows lower currents to be measured more accurately. This is because offsets become less significant when the sense voltage is larger. For best performance, select RSENSE to provide approximately 75mV (gain of 50V/V) or 50mV (gain of 100V/V) of sense voltage for the full-scale current in each application. Efficiency and Power Dissipation: At high-current levels, the I2R losses in RSENSE can be significant. Take this into consideration when choosing the resistor value and its power dissipation (wattage) rating. Also, the sense resistor's value might drift if it is allowed to heat up excessively. Inductance: Keep inductance low if ISENSE has a large high-frequency component. Wire-wound resistors have the highest inductance, while metal film is somewhat better. Low-inductance metal-film resistors are also available. Instead of being spiral-wrapped round a
Recommended Component Values
Ideally, the maximum load current develops the fullscale sense voltage across the current-sense resistor. Choose the gain needed to yield the maximum output voltage required for the application: VOUT = VSENSE x AV where VSENSE is the full-scale sense voltage, 75mV for gain of 50V/V, or 50mV for gain of 100V/V. AV is the gain of the device. In applications monitoring high current, ensure that RSENSE is able to dissipate its own I2R loss. If the resistor's power dissipation is exceeded, its value may drift or it may fail altogether, causing a differential voltage across the terminals in excess of the absolute maximum ratings. Use resistors specified for current- sensing applications.
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11
Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Table 1. Recommended Component Values
FULL-SCALE CURRENT (A) 0.075 0.05 0.75 0.5 3.75 2.5 7.5 5.0 15.0 10.0 CURRENT-SENSE RESISTOR (m) 1000 100 20 10 5 GAIN (V/V) 50 100 50 100 50 100 50 100 50 100 VSENSE (mV) 75 50 75 50 75 50 75 50 75 50 FULL-SCALE OUTPUT VOLTAGE WITH RESPECT TO REF (V) 3.75 5.0 3.75 5.0 3.75 5.0 3.75 5.0 3.75 5.0
core, as in metal-film or wire-wound resistors, they are a straight band of metal and are available in values under 1. Peak Current: The maximum current through RSENSE must be limited to: IPEAK = 0.3V / (RSENSE + RTRACE) where RTRACE is the total stray resistance from RS+ and RS- to RSENSE. To prevent forwarding the back-toback diodes between the differential input, the absolute maximum of the differential input voltage is 0.3V.
Power-Supply Bypassing and Grounding
The MAX4069-MAX4072 do not require special bypassing and respond quickly to transient changes in line current. You can place a large capacitor at the RSterminal (or "load" side) to decouple the load and, thereby, reduce the current transients. These capacitors are not required for operation or stability and their use does not degrade performance. The MAX4069-MAX4072 have been designed as a highside current monitor to ease the task of grounding any battery charger, thermistor, etc., that may be a part of the battery pack. Grounding these devices requires no special precautions; follow the same cautionary steps that apply to the system as a whole. High-current systems can experience large voltage drops across a ground plane, and this drop may add to or subtract from VOUT. Using differential measurement between VOUT and REF prevents this problem. For highest current-measurement accuracy, use a single-point star ground. On thin QFN packages, there is an exposed paddle that does not carry any current, but should also be connected to the ground plane for rated power dissipation.
Dynamic Range Considerations
Although the MAX4069-MAX4072 have fully symmetrical, bidirectional, VSENSE input capability, the outputvoltage range is usually higher from REF to VCC and lower from REF to GND (unless the supply voltage is at the lowest end of the operating range). Therefore, the user must consider the dynamic range of current monitored in both directions and choose the supply voltage and the reference voltage (REFOUT or REFIN) to make sure the output swing above and below REF is adequate to handle the swings without clipping or running out of headroom.
Shutdown Mode
When SHDN is low, the MAX4069-MAX4072 are shut down and consume only 10A. In shutdown mode, OUT is high impedance and turns off. Connect SHDN to VCC for normal operation.
12
______________________________________________________________________________________
Bidirectional, High-Side, Current-Sense Amplifiers with Reference
Pin Configurations
TOP VIEW
SHDN 1 RSRS+ N.C. GND 2 3 4 5 10 GSEL 9 VCC OUT REFOUT ADJ GND 4 SHDN 1 RS- 2 RS+ 3 8 7 GSEL VCC OUT REFOUT (REFIN)
MAX4069-MAX4072
MAX4069
8 7 6
MAX4070 MAX4071 MAX4072
6 5
MAX
Thin QFN/MAX
(REFIN) FOR MAX4072 ONLY.
Layout
In order to dissipate sense-resistor heat from large sense currents, solder the RS+ and the RS- pins to large copper traces. Keep the part away from other heat-generating devices. For accurate measurement of V SENSE , the Kelvin method is recommended. The current into RS+ and RSis only a few microamps; therefore, a short distance from RS+ and RS- pins does not cause significant errors. It is recommended to keep the value of RSENSE reasonably higher than the values of the trace's resistance. TRANSISTOR COUNT: 338 PROCESS: BiCMOS
Chip Information
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13
Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
6, 8, &10L, QFN THIN.EPS
PACKAGE OUTLINE, 6, 8 & 10L, QFN THIN (DUAL), EXPOSED PAD, 3x3x0.80 mm
21-0137
C
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
0.25 MIN 0.20 REF.
PACKAGE VARIATIONS PKG. CODE T633-1 T833-1 T1033-1 N 6 8 10 D2 1.500.10 1.500.10 1.500.10 E2 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.65 BSC 0.50 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEC MO229 / WEED-3 b 0.400.05 0.300.05 0.250.05 [(N/2)-1] x e 1.90 REF 1.95 REF 2.00 REF
PACKAGE OUTLINE, 6, 8 & 10L, QFN THIN (DUAL), EXPOSED PAD, 3x3x0.80 mm
21-0137
C
14
______________________________________________________________________________________
Bidirectional, High-Side, Current-Sense Amplifiers with Reference
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
MAX4069-MAX4072
4X S
8
8
INCHES DIM A A1 A2 b MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1
E
H
0.60.1
c D e E H L
1
1
0.60.1
S
D
BOTTOM VIEW
0.010 0.014 0.005 0.007 0.116 0.120 0.0256 BSC 0.116 0.120 0.188 0.198 0.016 0.026 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
1 1
J
______________________________________________________________________________________
15
Bidirectional, High-Side, Current-Sense Amplifiers with Reference MAX4069-MAX4072
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
10LUMAX.EPS
1 1
e
10
4X S
10
INCHES MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 D1 0.116 0.120 0.114 0.118 D2 0.116 E1 0.120 E2 0.114 0.118 H 0.187 0.199 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S 0 6
MILLIMETERS MAX MIN 1.10 0.15 0.05 0.75 0.95 3.05 2.95 3.00 2.89 3.05 2.95 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0 6
H y 0.500.1 0.60.1
1
1
0.60.1
TOP VIEW
BOTTOM VIEW
D2 GAGE PLANE A2 A b A1 D1
E2
c
E1 L1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0061
I
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 ____________________ 16 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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