19-2562; Rev 3; 5/10 KIT ATION EVALU E L B A IL AVA 76V, High-Side, Current-Sense Amplifiers with Voltage Output The MAX4080/MAX4081 are high-side, current-sense amplifiers with an input voltage range that extends from 4.5V to 76V making them ideal for telecom, automotive, backplane, and other systems where high-voltage current monitoring is critical. The MAX4080 is designed for unidirectional current-sense applications and the MAX4081 allows bidirectional current sensing. The MAX4081 single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX4081 requires an external reference to set the zero-current output level (VSENSE = 0V). The charging current is represented by an output voltage from VREF to VCC, while discharge current is given from VREF to GND. For maximum versatility, the 76V input voltage range applies independently to both supply voltage (VCC) and common-mode input voltage (V RS+). High-side current monitoring does not interfere with the ground path of the load being measured, making the MAX4080/MAX4081 particularly useful in a wide range of high-voltage systems. The combination of three gain versions (5V/V, 20V/V, 60V/V = F, T, S suffix) and a user-selectable, external sense resistor sets the full-scale current reading and its proportional output voltage. The MAX4080/MAX4081 offer a high level of integration, resulting in a simple, accurate, and compact current-sense solution. The MAX4080/MAX4081 operate from a 4.5V to 76V single supply and draw only 75µA of supply current. These devices are specified over the automotive operating temperature range (-40°C to +125°C) and are available in a space-saving 8-pin µMAX® or SO package. Applications Automotive (12V, 24V, or 42V Batteries) Features Wide 4.5V to 76V Input Common-Mode Range Bidirectional or Unidirectional ISENSE Low-Cost, Compact, Current-Sense Solution Three Gain Versions Available 5V/V (MAX4080F/MAX4081F) 20V/V (MAX4080T/MAX4081T) 60V/V (MAX4080S/MAX4081S) ±0.1% Full-Scale Accuracy Low 100µV Input Offset Voltage Independent Operating Supply Voltage 75µA Supply Current (MAX4080) Reference Input for Bidirectional OUT (MAX4081) Available in a Space-Saving, 8-Pin µMAX Package Ordering Information TEMP RANGE PIN-PACKAGE MAX4080FAUA+ PART -40°C to +125°C 8 µMAX MAX4080FASA+ -40°C to +125°C 8 SO MAX4080TAUA+ -40°C to +125°C 8 µMAX MAX4080TASA+ -40°C to +125°C 8 SO MAX4080SAUA+ -40°C to +125°C 8 µMAX MAX4080SASA+ -40°C to +125°C 8 SO MAX4081FAUA+ -40°C to +125°C 8 µMAX MAX4081FASA+ -40°C to +125°C 8 SO MAX4081TAUA+ -40°C to +125°C 8 µMAX MAX4081TASA+ -40°C to +125°C 8 SO MAX4081SAUA+ -40°C to +125°C 8 µMAX MAX4081SASA+ -40°C to +125°C 8 SO +Denotes a lead(Pb)-free/RoHS-compliant package. Selector Guide appears at end of data sheet. 48V Telecom and Backplane Current Measurement Pin Configurations Bidirectional Motor Control Power-Management Systems TOP VIEW + Avalanche Photodiode and PIN-Diode Current Monitoring RS+ 1 General System/Board-Level Current Sensing VCC 2 Precision High-Voltage Current Sources N.C. µMAX is a registered trademark of Maxim Integrated Products, Inc. + 8 RS- RS+ 1 7 N.C. VCC 2 MAX4080 8 RS- 7 REF1A MAX4081 3 6 N.C. N.C. 3 6 REF1B GND 4 5 OUT GND 4 5 OUT μMAX/SO μMAX/SO ________________________________________________________________ Maxim Integrated Products 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. 1 MAX4080/MAX4081 General Description MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output ABSOLUTE MAXIMUM RATINGS VCC to GND ............................................................-0.3V to +80V RS+, RS- to GND....................................................-0.3V to +80V OUT to GND.............-0.3V to the lesser of +18V or (VCC + 0.3V) REF1A, REF1B to GND (MAX4081 Only)....-0.3V to the lesser of +18V or (VCC + 0.3V) Output Short Circuit to GND.......................................Continuous Differential Input Voltage (VRS+ - VRS-) ...............................±80V Current into Any Pin..........................................................±20mA Continuous Power Dissipation (TA = +70°C) 8-Pin µMAX (derate 4.5mW/°C above +70°C) .............362mW 8-Pin SO (derate 5.88mW/°C above +70°C)................471mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°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. DC ELECTRICAL CHARACTERISTICS (VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0, RLOAD = 100kΩ, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER Operating Voltage Range Common-Mode Range Supply Current SYMBOL VCC CMVR ICC CONDITIONS 76 V 4.5 76 V VCC = VRS+ = 76V, no load MAX4080 75 190 MAX4081 103 190 IRS+, IRS- VCC = 0V, VRS+ = 76V VCC = VRS+ = 76V Gain Accuracy AV ΔAV 2 µA 5 12 µA MAX4080F/MAX4081F ±1000 MAX4080T/MAX4081T ±250 MAX4080S/MAX4081S ±100 MAX4080F/MAX4081F 5 MAX4080T/MAX4081T 20 MAX4080S/MAX4081S 60 VCC = VRS+ = 48V (Note 5) ±0.1 TA = +25°C VOS VCC = VRS+ = 48V (Note 6) µA 0.01 mV V/V ±0.6 ±1 TA = -40°C to +85°C % ±1.2 TA = TMIN to TMAX Input Offset Voltage UNITS 4.5 IRS+, IRS- Gain MAX Inferred from CMRR test (Note 3) Input Bias Current VSENSE TYP Inferred from PSRR test Leakage Current Full-Scale Sense Voltage (Note 4) MIN ±0.1 TA = +25°C ±0.6 ±1 TA = -40°C to +85°C mV ±1.2 TA = TMIN to TMAX Common-Mode Rejection Ratio CMRR VCC = 48V, VRS+ = 4.5V to 76V 100 124 dB Power-Supply Rejection Ratio PSRR VRS+ = 48V, VCC = 4.5V to 76V 100 122 dB OUT High Voltage 2 (VCC VOH) VCC = 4.5V, VRS+ = 48V, VREF1A = VREF1B = 2.5V, IOUT (sourcing) = +500µA (Note 8) MAX4080F/MAX4081F, VSENSE = 1000mV MAX4080T/MAX4081T, VSENSE = 250mV 0.15 MAX4080S/MAX4081S, VSENSE = 100mV _______________________________________________________________________________________ 0.27 V 76V, High-Side, Current-Sense Amplifiers with Voltage Output (VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0, RLOAD = 100kΩ, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER OUT Low Voltage REF1A = REF1B Input Voltage Range (MAX4081 Only) SYMBOL CONDITIONS VOL VCC = VRS+ = 48V, VREF1A = VREF1B = IOUT (sinking) = 10µA 2.5V, VSENSE = IOUT (sinking) = -1000mV (for 100µA MAX4081 only) MIN TYP MAX 4 15 UNITS mV 23 55 (VREF GND) Inferred from REF1A rejection ratio, VREF1A = VREF1B 1.5 6 V (VREF1A GND) Inferred from REF1A rejection ratio, VREF1B = GND 3 12 V REF1A Rejection Ratio (MAX4081 Only) VCC = VRS+ = 48V, VSENSE = 0V, VREF1A = VREF1B = 1.5V to 6V 80 108 REF/REF1A Ratio (MAX4081 Only) VREF1A = 10V, VREF1B = GND, VCC = VRS+ = 48V (Note 2) 0.497 0.500 REF1A Input Impedance (MAX4081 Only) VREF1B = GND REF1A Input Voltage Range (MAX4081 Only) 250 dB 0.503 kΩ _______________________________________________________________________________________ 3 MAX4080/MAX4081 DC ELECTRICAL CHARACTERISTICS (continued) MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output AC ELECTRICAL CHARACTERISTICS (VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0, RLOAD = 100kΩ, CLOAD = 20pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2) PARAMETER Bandwidth SYMBOL BW CONDITION VCC = VRS+ = 48V, VOUT = 2.5V MIN TYP MAX4080F/T/S 250 MAX4081F/T/S 150 MAX UNITS kHz VSENSE = 10mV to 100mV 20 VSENSE = 100mV to 10mV 20 No sustained oscillations 500 VSENSE = 100mV 0.1 Ω Power-Up Time VCC = VRS+ = 48V, VSENSE = 100mV (Note 9) 50 µs Saturation Recovery Time (Notes 9,10) 50 µs OUT Settling Time to 1% of Final Value Capacitive-Load Stability Output Resistance ROUT µs pF Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design. Note 2: VREF is defined as the average voltage of VREF1A and VREF1B. REF1B is usually connected to REF1A or GND. VSENSE is defined as VRS+ - VRS-. Note 3: The common-mode range at the low end of 4.5V applies to the most positive potential at RS+ or RS-. Depending on the polarity of VSENSE and the device’s gain, either RS+ or RS- can extend below 4.5V by the device’s typical full-scale value of VSENSE. Note 4: Negative VSENSE applies to MAX4081 only. Note 5: VSENSE is: MAX4080F, 10mV to 1000mV MAX4080T, 10mV to 250mV MAX4080S, 10mV to 100mV MAX4081F, -500mV to +500mV MAX4081T, -125mV to +125mV MAX4081S, -50mV to +50mV Note 6: VOS is extrapolated from the gain accuracy test for the MAX4080 and measured as (VOUT - VREF)/AV at VSENSE = 0V, for the MAX4081. Note 7: VSENSE is: MAX4080F, 500mV MAX4080T, 125mV MAX4080S, 50mV MAX4081F/T/S, 0V VREF1B = VREF1A = 2.5V Note 8: Output voltage is internally clamped not to exceed 18V. Note 9: Output settles to within 1% of final value. Note 10: The device will not experience phase reversal when overdriven. 4 _______________________________________________________________________________________ 76V, High-Side, Current-Sense Amplifiers with Voltage Output 20 15 10 5 -100 -150 -200 -125 -100 -75 -50 -25 0 25 50 75 100 125 -0.15 F VERSION -0.20 16 28 40 52 64 0 -0.1 -0.2 50 75 100 125 150 TEMPERATURE (°C) -50 1 10 100 1k 10k 100k 25 50 75 100 125 TEMPERATURE (°C) MAX4080 toc06 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 1 1M 10 100 1k 10k 100k 1M FREQUENCY (Hz) FREQUENCY (Hz) MAX4081F/T/S REFERENCE REJECTION RATIO vs. FREQUENCY MAX4080F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY MAX4081F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY -20 40 35 -50 30 GAIN (dB) -30 -40 -60 -70 VSENSE = 10mV 45 50 40 MAX4080T 25 20 30 20 -100 -110 5 5 0 0 MAX4080F 100 1k 10k 100k MAX4081F 15 10 10 FREQUENCY (Hz) MAX4081T 25 15 10 MAX4081S 35 -80 -90 -120 VOUT = 100mVP-P 45 MAX4080S MAX4080 toc09 50 MAX4080 toc07 0 1 0 MAX4081F/T/S POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 76 -25 VCC (V) -10 REFERENCE REJECTION RATIO (dB) 25 GAIN (dB) 4 0.1 -0.5 0 POWER-SUPPLY REJECTION RATIO (dB) T VERSION -0.10 0.2 -0.4 MAX4080 toc05 MAX4080 toc04 -0.05 COMMON-MODE REJECTION RATIO (dB) GAIN ACCURACY (%) S VERSION 0.3 MAX4081F/T/S COMMON-MODE REJECTION RATIO vs. FREQUENCY GAIN ACCURACY vs. VCC VRS+ = 48V 0.4 -0.3 INPUT OFFSET VOLTAGE (μV) 0 MAX4080 toc03 MAX4080 toc02 50 0 -50 -250 -300 -50 -25 0 0.5 GAIN ACCURACY (%) 25 250 200 150 100 MAX4080 toc08 PERCENTAGE (%) 30 300 INPUT OFFSET VOLTAGE (μV) MAX4080 toc01 35 0.1 1 10 FREQUENCY (kHz) 100 1000 0.1 1 10 100 1000 FREQUENCY (kHz) _______________________________________________________________________________________ 5 MAX4080/MAX4081 Typical Operating Characteristics (VCC = VRS+ = 48V, VSENSE = 0, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.) INPUT OFFSET VOLTAGE INPUT OFFSET VOLTAGE HISTOGRAM vs. TEMPERATURE GAIN ACCURACY vs. TEMPERATURE Typical Operating Characteristics (continued) (VCC = VRS+ = 48V, VSENSE = 0, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.) 75 70 115 115 110 105 100 110 105 95 65 28 40 52 64 76 85 80 65 4 16 28 40 52 64 -50 76 0 25 50 75 TEMPERATURE (°C) MAX4081 SUPPLY CURRENT vs. TEMPERATURE VOUT HIGH VOLTAGE vs. IOUT (SOURCING) VOUT LOW VOLTAGE vs. IOUT (SINKING) 95 90 85 80 75 70 TA = +125°C 0.35 0.30 TA = +85°C 0.25 TA = +25°C 0.20 0.15 0.10 TA = 0°C TA = -40°C 0.05 65 -50 -25 0 25 50 75 100 125 0 TEMPERATURE (°C) VCC = 4.5V 250 200 150 TA = +25°C 50 TA = 0°C TA = -40°C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 50 100 150 200 250 300 350 400 450 500 IOUT (SINKING) (μA) MAX4080S SMALL-SIGNAL TRANSIENT RESPONSE MAX4080T SMALL-SIGNAL TRANSIENT RESPONSE MAX4080 toc16 MAX4080 toc18 MAX4080 toc17 INPUT 5mV/div INPUT 5mV/div INPUT 5mV/div OUTPUT 25mV/div OUTPUT 100mV/div OUTPUT 300mV/div 20μs/div TA = +85°C 100 IOUT (SOURCING) (mA) MAX4080F SMALL-SIGNAL TRANSIENT RESPONSE TA = +125°C 0 0 20μs/div 125 MAX4080 toc15 0.40 100 300 MAX4080 toc14 VCC = 4.5V 0.45 VOUT LOW VOLTAGE (mV) 100 0.50 VOUT HIGH VOLTAGE (VCC - VOH) (V) 105 6 -25 VCC (V) VREF1A = VREF1B = 2.5V 110 90 VCC (V) MAX4080 toc13 115 16 95 70 85 4 100 75 90 60 MAX4080 toc12 120 SUPPLY CURRENT (μA) 80 VREF = 2.5V NO LOAD VSENSE = 0V SUPPLY CURRENT (μA) NO LOAD VSENSE = 0V MAX4080 toc11 125 MAX4080 toc10 85 SUPPLY CURRENT (μA) MAX4080 SUPPLY CURRENT vs. TEMPERATURE MAX4081 SUPPLY CURRENT vs. VCC MAX4080 SUPPLY CURRENT vs. VCC SUPPLY CURRENT (μA) MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output 20μs/div _______________________________________________________________________________________ 76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4081F SMALL-SIGNAL TRANSIENT RESPONSE MAX4081S SMALL-SIGNAL TRANSIENT RESPONSE MAX4081T SMALL-SIGNAL TRANSIENT RESPONSE MAX4080 toc19 MAX4080 toc21 MAX4080 toc20 INPUT 10mV/div INPUT 2.5mV/div INPUT 1mV/div OUTPUT 50mV/div OUTPUT 50mV/div OUTPUT 50mV/div 20μs/div 20μs/div 20μs/div MAX4080F LARGE-SIGNAL TRANSIENT RESPONSE MAX4080T LARGE-SIGNAL TRANSIENT RESPONSE MAX4080S LARGE-SIGNAL TRANSIENT RESPONSE MAX4080 toc22 MAX4080 toc24 MAX4080 toc23 INPUT 400mV/div INPUT 100mV/div INPUT 33mV/div OUTPUT 2V/div OUTPUT 2V/div OUTPUT 2V/div 20μs/div 20μs/div 20μs/div MAX4081F LARGE-SIGNAL TRANSIENT RESPONSE MAX4081S LARGE-SIGNAL TRANSIENT RESPONSE MAX4081T LARGE-SIGNAL TRANSIENT RESPONSE MAX4080 toc25 MAX4080 toc27 MAX4080 toc26 INPUT 400mV/div INPUT 100mV/div INPUT 33mV/div OUTPUT 2V/div OUTPUT 2V/div OUTPUT 2V/div 20μs/div 20μs/div 20μs/div _______________________________________________________________________________________ 7 MAX4080/MAX4081 Typical Operating Characteristics (continued) (VCC = VRS+ = 48V, VSENSE = 0, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.) MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output Typical Operating Characteristics (continued) (VCC = VRS+ = 48V, VSENSE = 0, CLOAD = 20pF, RLOAD = ∞, TA = +25°C, unless otherwise noted.) VCC-TRANSIENT RESPONSE MAX4080 toc28 VCC = 40V VRS+ = 20V VCC = 20V STEP VREF1 = VREF2 = 2.5V MAX4080 toc29 VCC 5V/div INPUT 500mV/div VCC (0 TO 10V) 5V/div OUTPUT 2V/div OUTPUT 2.5V/div VCC = 20V VOUT 1V/div 4μs/div 8 MAX4080T STARTUP DELAY (VSENSE = 250mV) MAX4080F SATURATION RECOVERY RESPONSE (VCC = 4.5V) 20μs/div 100μs/div _______________________________________________________________________________________ MAX4080 toc30 76V, High-Side, Current-Sense Amplifiers with Voltage Output PIN NAME FUNCTION MAX4080 MAX4081 1 1 RS+ Power connection to the external-sense resistor. 2 2 VCC Supply Voltage Input. Decouple VCC to GND with at least a 0.1µF capacitor to bypass line transients. 3, 6, 7 3 N.C. No Connection. No internal connection. Leave open or connect to ground. 4 4 GND Ground 5 5 OUT Voltage Output. For the unidirectional MAX4080, VOUT is proportional to VSENSE. For the bidirectional MAX4081, the difference voltage (VOUT - VREF) is proportional to VSENSE and indicates the correct polarity. 8 8 RS- Load connection to the external sense resistor. — 6 REF1B Reference Voltage Input: Connect REF1B to REF1A or to GND (see the External Reference section). — 7 REF1A Reference Voltage Input: Connect REF1A and REF1B to a fixed reference voltage (VREF). VOUT is equal to VREF when VSENSE is zero (see the External Reference section). Detailed Description The MAX4080/MAX4081 unidirectional and bidirectional high-side, current-sense amplifiers feature a 4.5V to 76V input common-mode range that is independent of supply voltage. This feature allows the monitoring of current out of a battery as low as 4.5V and also enables high-side current sensing at voltages greater than the supply voltage (VCC). The MAX4080/MAX4081 monitors current through a current-sense resistor and amplifies the voltage across the resistor. The MAX4080 senses current unidirectionally, while the MAX4081 senses current bidirectionally. The 76V input voltage range of the MAX4080/MAX4081 applies independently to both supply voltage (VCC) and common-mode, input-sense voltage (VRS+). Highside current monitoring does not interfere with the ground path of the load being measured, making the MAX4080/MAX4081 particularly useful in a wide range of high-voltage systems. Battery-powered systems require a precise bidirectional current-sense amplifier to accurately monitor the battery’s charge and discharge. The MAX4081 charging current is represented by an output voltage from VREF to VCC, while discharge current is given from VREF to GND. Measurements of OUT with respect to VREF yield a positive and negative voltage during charge and discharge, as illustrated in Figure 1 for the MAX4081T. Current Monitoring The MAX4080 operates as follows: current from the source flows through RSENSE to the load (Figure 2), creating a sense voltage, VSENSE. 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 VSENSE. The internal current mirror multiplies IRG1 by a current gain factor, β, to give IA2 = β IRG1. Amplifier A2 is used to convert the output current to a voltage and then sent through amplifier A3. Total gain = 5V/V for MAX4080F, 20V/V for the MAX4080T, and 60V/V for the MAX4080S. The MAX4081 input stage differs slightly from the MAX4080 (Figure 3). Its topology allows for monitoring of bidirectional currents through the sense resistor. When current flows from RS+ to RS-, the MAX4081 matches the voltage drop across the external sense resistor, RSENSE, by increasing the current through the Q1 and RG1. 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 MAX4081, the output signal of amplifier A2 is levelshifted to the reference voltage (V REF = V REF1A = VREF1B), resulting in a voltage at the output pin (OUT) _______________________________________________________________________________________ 9 MAX4080/MAX4081 Pin Description 10V 4.5V TO 76V BATTERY ILOAD ICHARGE VSENSE RSENSE RS- CHARGE CURRENT SYSTEM LOAD AND CHARGER 5V RS+ VOUT - VREF MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output VOUT = 10V VCC VSENSE MAX4081T REF1A -250mV 250mV 5V REF1B GND -5V VOUT = GND VREF1A = VREF1B = 5V OUT DISCHARGE CURRENT Figure 1. MAX4081T OUT Transfer Curve VSENSE VSENSE ILOAD RSENSE RS+ RS- RG1 RG2 RS+ RS- RG1 RG2 MAX4081 RF A1 MAX4080 A1 Q1 Q2 CURRENT MIRROR CURRENT MIRROR A2 OUT Q1 CURRENT MIRROR IA2 A2 A3 125kΩ REF1B 125kΩ OUT REF1A VREF GND Figure 2. MAX4080 Functional Diagram Figure 3. MAX4081 Functional Diagram that swings above VREF voltage for positive-sense voltages and below V REF for negative-sense voltages. VOUT is equal to VREF when VSENSE is equal to zero. Set the full-scale output range by selecting RSENSE and the appropriate gain version of the MAX4080/ MAX4081. Note: For Gain = 5 (F), RG1 = RG2 = 160k. For Gain = 20 (T), RG1 = RG2 = 60k. For Gain = 60 (S), RG1 = RG2 = 20k. 10 ______________________________________________________________________________________ 76V, High-Side, Current-Sense Amplifiers with Voltage Output FULL-SCALE VSENSE (mV) MAX4081 FULL-SCALE OUTPUT VOLTAGE (VOUT - VREF, V) 5 ±500 ±2.5 20 ±125 ±2.5 ±50 ±3.0 5 ±500 ±2.5 20 ±125 ±2.5 ±50 ±3.0 FULL-SCALE LOAD CURRENT, ILOAD (A) CURRENT-SENSE RESISTOR (mΩ) GAIN (V/V) 0.500 1000 0.125 1000 0.050 1000 60 5.000 100 1.250 100 0.500 100 60 50.000 10 5 ±500 ±2.5 12.500 10 20 ±125 ±2.5 5.000 10 60 ±50 ±3.0 FULL-SCALE LOAD CURRENT, ILOAD (A) CURRENT-SENSE RESISTOR (mΩ) GAIN (V/V) FULL-SCALE VSENSE (mV) MAX4080 FULL-SCALE OUTPUT VOLTAGE (V) 1.000 1000 5 1000 5.0 0.250 1000 20 250 5.0 0.100 1000 60 100 6.0 10.000 100 5 1000 5.0 2.500 100 20 250 5.0 1.000 100 60 100 6.0 50.000 10 5 500 2.5 25.000 10 20 250 5.0 10.000 10 60 100 6.0 External References (MAX4081) For the bidirectional MAX4081, the VOUT reference level is controlled by REF1A and REF1B. VREF is defined as the average voltage of VREF1A and VREF1B. Connect REF1A and REF1B to a low-noise, regulated voltage source to set the output reference level. In this mode, VOUT equals VREF1A when VSENSE equals zero (see Figure 4). Alternatively, connect REF1B to ground, and REF1A to a low-noise, regulated voltage source. In this case, the output reference level (VREF) is equal to VREF1A divided by two. VOUT equals VREF1A/2 when VSENSE equals zero. In either mode, the output swings above the reference voltage for positive current-sensing (VRS+ > VRS-). The output swings below the reference voltage for negative current-sensing (VRS+ < VRS-). MAX4080/MAX4081 Table 1. Typical Component Values Applications Information 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 AV where VSENSE is the full-scale sense voltage, 1000mV for gain of 5V/V, 250mV for gain of 20V/V, 100mV for gain of 60V/V, and AV is the gain of the device. In applications monitoring a 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. The MAX4080/MAX4081 sense a wide variety of currents with different sense-resistor values. Table 1 lists common resistor values for typical operation. ______________________________________________________________________________________ 11 MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output ILOAD = 0 ILOAD = 0 RSENSE RSENSE LOAD RS+ LOAD RS- RS+ VCC RS- VCC REF1A REF1A 10V MAX4081 MAX4081 5V REF1B REF1B GND OUT 5V GND OUT 5V Figure 4. MAX4081 Reference Inputs The full-scale output voltage is VOUT = RSENSE ILOAD (MAX) A V , for the MAX4080 and V OUT = V REF ± R SENSE I LOAD(MAX) A V for the MAX4081. V SENSE(MAX) is 1000mV for the 5V/V gain version, 250mV for the 20V/V gain version, and 100mV for the 60V/V gain version. Because of the high currents that flow through RSENSE, take care to eliminate parasitic trace resistance from causing errors in the sense voltage. Either use a fourterminal current-sense resistor or use Kelvin (force and sense) PC board layout techniques. Choosing the Sense Resistor Although the MAX4081 have fully symmetrical bidirectional VSENSE input capability, the output voltage 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 (REF) to make sure the output swing above and below REF is adequate to handle the swings without clipping or running out of headroom. Choose RSENSE based on the following criteria: • Voltage Loss: A high R SENSE value causes the power-source 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 due to offsets becoming less significant when the sense voltage is larger. For best performance, select RSENSE to provide approximately 1000mV (gain of 5V/V), 250mV (gain of 20V/V), or 100mV (gain of 60V/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 spiralwrapped around a core, as in metal-film or wirewound resistors, they are a straight band of metal and are available in values under 1Ω. 12 Dynamic Range Consideration Power-Supply Bypassing and Grounding For most applications, bypass VCC to GND with a 0.1µF ceramic capacitor. In many applications, VCC can be connected to one of the current monitor terminals (RS+ or RS-). Because VCC is independent of the monitored voltage, VCC can be connected to a separate regulated supply. If VCC will be subject to fast-line transients, a series resistor can be added to the power-supply line of the MAX4080/MAX4081 to minimize output disturbance. This resistance and the decoupling capacitor reduce the rise time of the transient. For most applications, 1kΩ in conjunction with a 0.1µF bypass capacitor work well. The MAX4080/MAX4081 require no special considerations with respect to layout or grounding. Consideration should be given to minimizing errors due to the large charge and discharge currents in the system. ______________________________________________________________________________________ 76V, High-Side, Current-Sense Amplifiers with Voltage Output ISENSE SYSTEM LOAD VCC = 4.5V TO 76V RSENSE RS+ RS- VCC MAX4080 RSENSE RS+ OUT GND RS- VCC MAX4081 REF1A GND REF1B SYSTEM POWER MANAGEMENT AND CHARGER CIRCUITRY 1.8V PROCESS: Bipolar MAX1243 ADC SERIAL INTERFACE Package Information μC Figure 5. MAX4081 Used In Smart-Battery Application Selector Guide PART Chip Information BATTERY OUT GAIN (V/V) ISENSE MAX4080FAUA 5 Unidirectional MAX4080FASA 5 Unidirectional MAX4080TAUA 20 Unidirectional MAX4080TASA 20 Unidirectional MAX4080SAUA 60 Unidirectional MAX4080SASA 60 Unidirectional MAX4081FAUA 5 Bidirectional MAX4081FASA 5 Bidirectional MAX4081TAUA 20 Bidirectional MAX4081TASA 20 Bidirectional MAX4081SAUA 60 Bidirectional MAX4081SASA 60 Bidirectional 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. 8 µMAX U8+1 21-0036 8 SO S8+2 21-0041 ______________________________________________________________________________________ 13 MAX4080/MAX4081 Typical Operating Circuit Power Management The bidirectional capability of the MAX4081 makes it an excellent candidate for use in smart battery packs. In the application diagram (Figure 5), the MAX4081 monitors the charging current into the battery as well as the discharge current out of the battery. The microcontroller stores this information, allowing the system to query the battery's status as needed to make system power-management decisions. MAX4080/MAX4081 76V, High-Side, Current-Sense Amplifiers with Voltage Output Revision History REVISION NUMBER REVISION DATE 0 10/02 Initial release — 1 11/08 Added values for RG1 and RG2 10 2 5/09 Added lead-free and automotive parts to Ordering Information 1 3 5/10 Removed automotive part and added soldering temperature DESCRIPTION PAGES CHANGED 1, 2 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. 14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.