19-1434; Rev 1; 5/99 Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier The MAX4173 low-cost, precision, high-side currentsense amplifier is available in a tiny SOT23-6 package. It features a voltage output that eliminates the need for gain-setting resistors and it is ideal for today’s notebook computers, cell phones, and other systems where current monitoring is critical. High-side current monitoring is especially useful in battery-powered systems, since it does not interfere with the ground path of the battery charger. The input common-mode range of 0 to +28V is independent of the supply voltage and ensures that the current-sense feedback remains viable even when connected to a battery in deep discharge. The MAX4173’s wide 1.7MHz bandwidth makes it suitable for use inside battery charger control loops. The combination of three gain versions and a userselectable external sense resistor sets the full-scale current reading. This feature offers a high level of integration, resulting in a simple and compact currentsense solution. The MAX4173 operates from a single +3V to +28V supply, typically draws only 420µA of supply current over the extended operating temperature range (-40°C to +85°C), and is offered in the space-saving SOT23-6 package. Features ♦ Low-Cost, Compact Current-Sense Solution ♦ Wide 0 to +28V Common-Mode Range Independent of Supply Voltage ♦ Three Gain Versions Available +20V/V (MAX4173T) +50V/V (MAX4173F) +100V/V (MAX4173H) ♦ ±0.5% Full-Scale Accuracy ♦ 420µA Supply Current ♦ Wide 1.7MHz Bandwidth (MAX4173T) ♦ +3V to +28V Operating Supply ♦ Available in Space-Saving SOT23-6 Package Applications Notebook Computers Portable/Battery-Powered Systems Smart Battery Packs/Chargers Cell Phones Power-Management Systems General System/Board-Level Current Monitoring PA Bias Control Precision Current Sources Typical Operating Circuit ILOAD VSENSE 0 TO +28V RSENSE RS+ +3V TO +28V RS- VCC 0.1µF MAX4173T/F/H A/D CONVERTER LOAD/ BATTERY OUT GND Ordering Information PART GAIN (V/V) TEMP. RANGE PIN-PACKAGE MAX4173TEUT-T 20 -40°C to +85°C 6 SOT23-6 MAX4173TESA 20 -40°C to +85°C 8 SO MAX4173FEUT-T 50 -40°C to +85°C 6 SOT23-6 MAX4173FESA 50 -40°C to +85°C 8 SO MAX4173HEUT-T 100 -40°C to +85°C 6 SOT23-6 MAX4173HESA 100 -40°C to +85°C 8 SO SOT TOP MARK AABN – AABD – AABP – Pin Configurations appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX4173T/F/H General Description MAX4173T/F/H Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier ABSOLUTE MAXIMUM RATINGS VCC, RS+, RS- to GND .......................................... -0.3V to +30V OUT to GND .............................................. -0.3V to (VCC + 0.3V) Output Short-Circuit to VCC or GND ......................... Continuous Differential Input Voltage (VRS+ - VRS-) ............................. ±0.3V Current into Any Pin......................................................... ±20mA Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.88mW/°C above +70°C)............... 471mW SOT23-6 (derate 8.7mW/°C above +70°C)................. 696mW Operating Temperature Range .......................... -40°C to +85°C Storage Temperature Range ............................ -65°C to +150°C Lead Temperature (soldering, 10sec) ............................ +300°C 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+ = 0 to +28V, VCC = +3V to +28V, VSENSE = 0, TA = TMIN to TMAX, RLOAD = ∞ unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Operating Voltage Range SYMBOL VCC CONDITIONS 3 0 Common-Mode Input Range VCMR (Note 2) Common-Mode Rejection CMR VRS+ > +2.0V Supply Current Leakage Current ICC IRS+, IRSIRS+ Input Bias Current IRSFull-Scale Sense Voltage VSENSE Total OUT Voltage Error (Note 3) OUT High Voltage (Note 5) 2 (VCC VOH) MIN Guaranteed by PSR test TYP MAX UNITS 28 V 28 90 VRS+ > +2.0V, VCC = 12V 0.42 VCC = 0 0.3 V dB 1.0 mA 3 µA VRS+ > +2.0V 0 50 VRS+ ≤ +2.0V -350 50 VRS+ > +2.0V 0 100 VRS+ ≤ +2.0V -700 µA 100 VSENSE = VRS+ - VRS- 150 mV VSENSE = +100mV, VCC = +12V, VRS+ = +12V ±0.5 5.75 VSENSE = +100mV, VCC = +12V, VRS+ = +12V, TA = +25°C 0.5 3.25 VSENSE = +100mV, VCC = +28V, VRS+ = +28V 0.5 5.75 VSENSE = +100mV, VCC = +12V, VRS+ = +0.1V -9 ±24 VCC = +12V, VRS+ =+12V, VSENSE = +6.25mV (Note 4) ±7.5 MAX4173T, VCC = +3.0V 0.8 1.2 MAX4173F, VCC = +7.5V 0.8 1.2 MAX4173H, VCC = +15V 0.8 1.2 _______________________________________________________________________________________ % V Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier (VRS+ = 0 to +28V, VCC = +3V to +28V, VSENSE = 0, TA = TMIN to TMAX, RLOAD = ∞ unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER Bandwidth SYMBOL BW Gain AV ∆AV Gain Accuracy OUT Settling Time to 1% of Final Value OUT Output Resistance Power-Supply Rejection CONDITIONS VRS+ = +12V, VCC = +12V, CLOAD = 5pF MIN MAX4173T, VSENSE = +100mV, 1.7 MAX4173F, VSENSE = +100mV, 1.4 MAX4173H, VSENSE = +100mV, 1.2 VSENSE = +6.25mV, (Note 4) 0.6 MAX UNITS MHz MAX4173T 20 MAX4173F 50 MAX4173H 100 MAX4173T/F VSENSE = +10mV to +150mV TA = -40°C to +85°C MAX4173H VSENSE = +10mV to +100mV TA = -40°C to +85°C TA = +25°C 0.5 VCC = +12V, VRS+ = +12V, CLOAD = 5pF VSENSE = +6.25mV to +100mV 400 VSENSE = +100mV to +6.25mV 800 V/V 4.0 TA = +25°C 0.5 ±2.5 % 4.0 ±2.5 ns ROUT PSR TYP 12 MAX4173T, VSENSE = 80mV, VRS+ ≥ +2V 60 84 MAX4173F, VSENSE = 32mV, VRS+ ≥ +2V 60 91 MAX4173H, VSENSE = 16mV, VRS+ ≥ +2V 60 95 kΩ dB Power-Up Time to 1% of Final Value VSENSE = +100mV, CLOAD = 5pF 10 µs Saturation Recovery Time VCC = +12V, VRS+ = +12V (Note 6) 10 µs Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design. Note 2: Guaranteed by Total Output Voltage Error Test. Note 3: Total OUT Voltage Error is the sum of gain and offset voltage errors. Note 4: +6.25mV = 1/16 of +100mV full-scale voltage. Note 5: VSENSE such that output stage is in saturation. Note 6: The device does not experience phase reversal when overdriven. _______________________________________________________________________________________ 3 MAX4173T/F/H ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25°C, unless otherwise noted.) MAX4173H 400 MAX4173F 390 400 MAX4173F 350 300 MAX4173H 15 20 25 30 SUPPLY VOLTAGE (V) TOTAL OUTPUT ERROR vs. SUPPLY VOLTAGE 0.30 MAX4173T 0 MAX4173H -0.15 MAX4173F -0.30 25 40 55 70 0 1.5 2.0 2.5 TOTAL OUTPUT ERROR vs. SUPPLY VOLTAGE TOTAL OUTPUT ERROR vs. FULL-SCALE SENSE VOLTAGE MAX4173H 0 MAX4173F -2 28 4 VCC = 28V 3 2 MAX4173H 1 0 MAX4173T -1 15 20 25 MAX4173F -2 0 30 5 10 15 20 25 30 -10 4 TOTAL OUTPUT ERROR (%) -20 -30 -40 -50 -60 -70 -80 MAX4173H 2 MAX4173T 0 -2 MAX4173F -4 1M 10M 200 0.8 MAX4173T MAX4173H 0.4 0 -0.4 MAX4173F -6 -0.8 -1.2 -10 -100 150 GAIN ACCURACY vs. TEMPERATURE -8 -90 FREQUENCY (Hz) 100 1.2 MAX4173 toc08 6 MAX4173 toc07 0 100k 50 VSENSE (mV) TOTAL OUTPUT ERROR vs. COMMON-MODE VOLTAGE POWER-SUPPLY REJECTION vs. FREQUENCY 10k 0 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) GAIN ACCURACY (%) 10 1k 1.0 VRS+ (V) -6 100 0.5 VSENSE = 6.25mV -0.60 5 MAX4173H TEMPERATURE (°C) MAX4173T 2 VSENSE = 100mV 0 MAX4173F 0.4 85 -4 -0.45 MAX4173T 0.6 MAX4173 toc09 0.15 10 4 TOTAL OUTPUT ERROR (%) 0.45 -5 6 MAX4173 toc04 0.60 0.8 0 -50 -35 -20 TOTAL OUTPUT ERROR (%) 10 MAX4173 toc05 5 1.0 0.2 150 0 MAX4173 toc03 1.2 200 370 TOTAL OUTPUT ERROR (%) MAX4173 toc02 MAX4173T 450 250 380 4 SUPPLY CURRENT vs. RS+ VOLTAGE 1.4 SUPPLY CURRENT (mA) 420 410 500 SUPPLY CURRENT (µA) SUPPLY CURRENT (µA) MAX4173 TOC01 MAX4173T 430 SUPPLY CURRENT vs. TEMPERATURE 550 MAX4173 toc06 SUPPLY CURRENT vs. SUPPLY VOLTAGE 440 PSR (dB) MAX4173T/F/H Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier 0 5 10 15 20 25 COMMON-MODE VOLTAGE (V) 30 -50 -35 -20 -5 10 25 40 TEMPERATURE (°C) _______________________________________________________________________________________ 55 70 85 Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier MAX4173 toc10 2.0 TOTAL OUTPUT ERROR (%) 1.5 1.0 0.5 MAX4173 toc11 MAX4173T LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV) TOTAL OUTPUT ERROR vs. TEMPERATURE CL = 5pF MAX4173H IN (45mV/div) MAX4173T 100mV 6mV 0 2V -0.5 MAX4173F OUT (500mV/div) -1.0 0.120V -1.5 -2.0 -50 -35 -20 -5 10 25 40 55 70 85 2µs/div TEMPERATURE (°C) CL = 5pF IN (45mV/div) MAX4173 toc13 MAX4173H LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV) MAX4173 toc12 MAX4173F LARGE-SIGNAL TRANSIENT RESPONSE (VSENSE = 6mV to 100mV) CL = 5pF 100mV 6mV IN (45mV/div) 100mV 6mV 10V 5V OUT (2V/div) OUT (3V/div) 0.6V 0.3V MAX4173T SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV TO 100mV) MAX4173F SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV TO 100mV) CL = 5pF IN (5mV/div) MAX4173 toc16 2µs/div MAX4173 toc14 2µs/div CL = 5pF 100mV 95mV IN (5mV/div) 100mV 95mV 2.0V 5V OUT (50mV/div) 1.9V OUT (100mV/div) 4.75V 2µs/div 2µs/div _______________________________________________________________________________________ 5 MAX4173T/F/H Typical Operating Characteristics (continued) (VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +12V, VRS+ = +12V, VSENSE = +100mV, TA = +25°C, unless otherwise noted.) MAX4173H SMALL-SIGNAL TRANSIENT RESPONSE (VSENSE = 95mV to 100mV) CL = 5pF IN (5mV/div) MAX4173 toc17 START-UP DELAY (VCC = 0 to 4V) (VSENSE = 100mV) MAX4173 toc15 MAX4173T/F/H Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier 100mV 95mV 4V IN (2V/div) 0V 2V 10V OUT (200mV/div) OUT (1V/div) 0V 9.5V 5µs/div 2µs/div Pin Description PIN NAME 6 FUNCTION SOT23-6 SO 1, 2 3 GND Ground 3 1 VCC Supply Voltage Input. Bypass to GND with a 0.1µF capacitor. 4 8 RS+ Power-Side Connection to the External Sense Resistor 5 6 RS- Load-Side Connection for the External Sense Resistor 6 4 OUT Voltage Output. VOUT is proportional to VSENSE ( VRS+ - VRS- ). Output impedance is approximately 12kΩ. – 2, 5, 7 N.C. No Connection. Not internally connected. _______________________________________________________________________________________ Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier The MAX4173 high-side current-sense amplifier features a 0 to +28V input common-mode range that is independent of supply voltage. This feature allows the monitoring of current out of a battery in deep discharge and also enables high-side current sensing at voltages greater than the supply voltage (VCC). The MAX4173 operates as follows: Current from the source flows through RSENSE to the load (Figure 1). Since the internal-sense amplifier’s inverting input has high impedance, negligible current flows through RG2 (neglecting the input bias current). Therefore, the sense amplifier’s inverting-input voltage equals VSOURCE - (ILOAD)(RSENSE). The amplifier’s open-loop gain forces its noninverting input to the same voltage as the inverting input. Therefore, the drop across RG1 equals (ILOAD)(RSENSE). Since IRG1 flows through RG1, IRG1 = (ILOAD)(RSENSE) / RG1. The internal current mirror multiplies I RG1 by a current gain factor, β, to give IRGD = β · IRG1. Solving IRGD = β · (ILOAD)(RSENSE) / RG1. Assuming infinite output impedance, VOUT = (IRGD) (RGD). Substituting in for IRGD and rearranging, VOUT = β · (RGD / RG1)(RSENSE · ILOAD). The parts gain equals β · RGD / RG1. Therefore, V OUT = (GAIN) (R SENSE) (ILOAD), where GAIN = 20 for MAX4173T, GAIN = 50 for MAX4173F, and GAIN = 100 for MAX4173H. RSENSE VSOURCE 0 TO +28V RS+ ILOAD TO LOAD BATTERY RS- IRG1 +3V TO +28V RG1 VCC RG2 MAX4173 OUT IRGD RGD = 12k GND Applications Information Recommended Component Values The MAX4173 senses a wide variety of currents with different sense resistor values. Table 1 lists common resistor values for typical operation of the MAX4173. Choosing RSENSE To measure lower currents more accurately, use a high value for RSENSE. The high value develops a higher sense voltage that reduces offset voltage errors of the internal op amp. In applications monitoring very high currents, RSENSE must be able to dissipate the I2R losses. If the resistor’s rated 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. If ISENSE has a large high-frequency component, minimize the inductance of RSENSE. Wire-wound resistors have the highest inductance, metal-film resistors are somewhat better, and low-inductance metal-film resistors are best suited for these applications. Using a PCB Trace as RSENSE If the cost of RSENSE is an issue and accuracy is not critical, use the alternative solution shown in Figure 2. This solution uses copper PC board traces to create a sense resistor. The resistivity of a 0.1-inch-wide trace of 2-ounce copper is approximately 30mΩ/ft. The resistance-temperature coefficient of copper is fairly high (approximately 0.4%/°C), so systems that experience a wide temperature variance must compensate for this effect. In addition, do not exceed the maximum power dissipation of the copper trace. For example, the MAX4173T (with a maximum load current of 10A and an RSENSE of 5mΩ) creates a full-scale VSENSE of 50mV that yields a maximum VOUT of 1V. RSENSE in this case requires about 2 inches of 0.1 inchwide copper trace. A1 CURRENT MIRROR Set the full-scale output range by selecting RSENSE and the appropriate gain version of the MAX4173. VOUT Output Impedance The output of the MAX4173 is a current source driving a 12kΩ resistance. Resistive loading added to OUT reduces the output gain of the MAX4173. To minimize output errors for most applications, connect OUT to a high-impedance input stage. When output buffering is required, choose an op amp with a common-mode input range and an output voltage swing that includes ground when operating with a single supply. The op Figure 1. Functional Diagram _______________________________________________________________________________________ 7 MAX4173T/F/H Detailed Description MAX4173T/F/H Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier Table 1. Recommended Component Values FULL-SCALE LOAD CURRENT ILOAD (A) CURRENT-SENSE RESISTOR RSENSE (mΩ) GAIN FULL-SCALE OUTPUT VOLTAGE (FULL-SCALE VSENSE = 100mV) VOUT (V) 20 2.0 0.1 1000 50 5.0 100 10.0 1 100 5 20 10 10 INPUT 0.1 in. COPPER + _ 0.3 in. COPPER VSENSE RS- RS+ 2.0 5.0 100 10.0 20 2.0 50 5.0 100 10.0 20 2.0 50 5.0 100 10.0 LOAD/BATTERY RSENSE 0.3 in. COPPER 20 50 VIN +3V TO +28V +3V TO +28V VCC 0.1µF ILOAD VSENSE LOW-COST 0 TO +28V SWITCHING REGULATOR RSENSE RS+ RS- VCC 0.1µF MAX4173 MAX4173T OUT LOAD/ BATTERY OUT GND GND Figure 2. MAX4173 Connections Showing Use of PC Board Figure 3. Current Source amp’s supply voltage range should be at least as high as any voltage the system may encounter. The percent error introduced by output loading is determined with the following formula: Figure 3 shows a block diagram using the MAX4173 with a switching regulator to make a current source. Current Source Circuit RLOAD %ERROR = 100 − 1 12kΩ + RLOAD where RLOAD is the external load applied to OUT. 8 _______________________________________________________________________________________ Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier TOP VIEW GND 1 GND 2 MAX4173 6 OUT 5 RS- VCC 1 8 RS+ 7 N.C. 3 6 RS- OUT 4 5 N.C. N.C. 2 GND VCC 3 4 SOT23-6 RS+ MAX4173 SO Chip Information TRANSISTOR COUNT: 187 _______________________________________________________________________________________ 9 MAX4173T/F/H Pin Configurations Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier 6LSOT.EPS MAX4173T/F/H Package Information 10 ______________________________________________________________________________________ Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier SOICN.EPS ______________________________________________________________________________________ 11 MAX4173T/F/H Package Information (continued) MAX4173T/F/H Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier NOTES 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. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.