EVALUATION KIT AVAILABLE MAX48/MAX481 General Description The MAX48/MAX481 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 MAX48 is designed for unidirectional current-sense applications and the MAX481 allows bidirectional current sensing. The MAX481 single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX481 requires an external reference to set the zero-current output level (V SENSE = V). The charging current is represented by an output voltage from V REF to, while discharge current is given from V REF to. For maximum versatility, the 76V input voltage range applies independently to both supply voltage ( ) and common-mode input voltage (V ). High-side current monitoring does not interfere with the ground path of the load being measured, making the MAX48/MAX481 particularly useful in a wide range of high-voltage systems. The combination of three gain versions (5V/V, 2V/V, 6V/V = F, T, S suffix) and a user-selectable, external sense resistor sets the full-scale current reading and its proportional output voltage. The MAX48/MAX481 offer a high level of integration, resulting in a simple, accurate, and compact current-sense solution. The MAX48/MAX481 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 (-4 C to +125 C) and are available in a space-saving 8-pin µmax or SO package. Applications Automotive (12V, 24V, or 42V Batteries) 48V Telecom and Backplane Current Measurement Bidirectional Motor Control Power-Management Systems Avalanche Photodiode and PIN-Diode Current Monitoring General System/Board-Level Current Sensing Precision High-Voltage Current Sources Benefits and Features Ideal for High-Voltage Current Monitoring Applications Wide 4.5V to 76V Input Common-Mode Range Independent Operating Supply Voltage High Accuracy and Low Quiescent Current Support Precision Application Requirements ±.1% Full-Scale Accuracy Low 1μV Input Offset Voltage Three Gain Versions Available -- 5V/V (MAX48F/MAX481F) -- 2V/V (MAX48T/MAX481T) -- 6V/V (MAX48S/MAX481S) 75μA Supply Current (MAX48) Flexible Current Sensing Supports Monitoring of Charge and Discharge of Batteries Bidirectional (MAX481) or Unidirectional (MAX48) I SENSE Reference Input for Bidirectional (MAX481) Minimizes Required Board Space 8-Pin μmax Package Ordering Information PART TEMP RANGE PIN-PACKAGE MAX48FAUA+ -4 C to +125 C 8 µmax MAX48FAUA/V+ -4 C to +125 C 8 µmax MAX48FASA+ -4 C to +125 C 8 SO MAX48TAUA+ -4 C to +125 C 8 µmax MAX48TAUA/V+ -4 C to +125 C 8 µmax +Denotes a lead(pb)-free/rohs-compliant package. /V denotes an automotive qualified part. Ordering Information continued at end of data sheet. Selector Guide appears at end of data sheet. Pin Configurations TOP VIEW N.C. 1 2 3 4 + MAX48 8 7 6 5 N.C. N.C. N.C. 1 2 3 4 + MAX481 8 7 6 5 REF1A REF1B µmax is a registered trademark of Maxim Integrated Products, Inc. µmax/so µmax/so 19-2562; Rev 5; 5/15
Absolute Maximum Ratings to...-.3v to +8V, to...-.3v to +8V to... -.3V to the lesser of +18V or ( +.3V) REF1A, REF1B to (MAX481 Only).-.3V to the lesser of +18V or ( +.3V) Output Short Circuit to...continuous Differential Input Voltage (V - V )...±8V Current into Any Pin...±2mA Continuous Power Dissipation (T A = +7 C) 8-Pin?MAX (derate 4.5mW/ C above +7 C)...362mW 8-Pin SO (derate 5.88mW/ C above +7 C)...471mW Operating Temperature Range... -4 C to +125 C Junction Temperature...+15 C Storage Temperature Range... -65 C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow)...+26 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 ( = V = 4.5V to 76V, V REF1A = V REF1B = 5V (MAX481 only), V SENSE = (V - V ) = V, R LOAD = 1kΩ, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating Voltage Range Inferred from PSRR test 4.5 76 V Common-Mode Range C MVR Inferred from CMRR test (Note 3) 4.5 76 V Supply Current I CC = V = 76V, no load MAX48 75 19 MAX481 13 19 Leakage Current I, I = V, V = 76V.1 2 µa Input Bias Current I, I = V = 76V 5 12 µa Full-Scale Sense Voltage (Note 4) V SENSE MAX48T/MAX481T ±25 MAX48F/MAX481F ±1 MAX48S/MAX481S ±1 Gain A V MAX48T/MAX481T 2 MAX48F/MAX481F 5 Gain Accuracy DA V = V = 48V (Note 5) Input Offset Voltage V OS = V = 48V (Note 6) Common-Mode Rejection Ratio (Note 7) MAX48S/MAX481S 6 T A = +25 C ±.1 ±.6 T A = -4 C to +85 C ±1 T A = T MIN to T MAX ±1.2 T A = +25 C ±.1 ±.6 T A = -4 C to +85 C ±1 T A = T MIN to T MAX ±1.2 CMRR = 48V, V = 4.5V to 76V 1 124 db µa mv V/V % mv Power-Supply Rejection Ratio (Note 7) PSRR V = 48V, = 4.5V to 76V 1 122 db High Voltage ( V OH ) = 4.5V, V = 48V, V REF1A = V REF1B = 2.5V, I (sourcing) = +5µA (Note 8) MAX48F/MAX481F, V SENSE = 1mV MAX48T/MAX481T, V SENSE = 25mV MAX48S/MAX481S, V SENSE = 1mV.15.27 V www.maximintegrated.com Maxim Integrated 2
DC Electrical Characteristics (continued) ( = V = 4.5V to 76V, V REF1A = V REF1B = 5V (MAX481 only), V SENSE = (V - V ) = V, R LOAD = 1kΩ, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Low Voltage V OL = V = 48V, V REF1A = V REF1B = 2.5V, V SENSE = -1mV (for MAX481 only) I (sinking) = 1µA 4 15 I (sinking) = 1µA 23 55 REF1A = REF1B Input Voltage Range (MAX481 Only) REF1A Input Voltage Range (MAX481 Only) (V REF V ) (V REF1A V ) Inferred from REF1A rejection ratio, V REF1A = V REF1B 1.5 6 V Inferred from REF1A rejection ratio, V REF1B = V 3 12 V REF1A Rejection Ratio (MAX481 Only) REF/REF1A Ratio (MAX481 Only) = V = 48V, V SENSE = V, V REF1A = V REF1B = 1.5V to 6V V REF1A = 1V, V REF1B = V, = V = 48V (Note 2) 8 18 db.497.5.53 REF1A Input Impedance (MAX481 Only) V REF1B = V 25 kw www.maximintegrated.com Maxim Integrated 3
AC Electrical Characteristics ( = V = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX481 only), VSENSE = (V - V) = V, RLOAD = 1kΩ, C LOAD = 2pF, T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C.) (Notes 1, 2) Bandwidth PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS Settling Time to 1% of Final Value BW = V = 48V, V = 2.5V MAX48F/T/S 25 MAX481F/T/S 15 V SENSE = 1mV to 1mV 2 V SENSE = 1mV to 1mV 2 Capacitive-Load Stability No sustained oscillations 5 pf Output Resistance R V SENSE = 1mV.1 W Power-Up Time = V = 48V, V SENSE = 1mV (Note 9) 5 µs Saturation Recovery Time (Notes 9,1) 5 µs Note 1: All devices are 1% production tested at T A = +25 C. All temperature limits are guaranteed by design. Note 2: V REF is defined as the average voltage of V REF1A and VREF1B. REF1B is usually connected to REF1A or. V SENSE is defined as V - V. Note 3: The common-mode range at the low end of 4.5V applies to the most positive potential at or. Depending on the polarity of V SENSE and the device s gain, either or can extend below 4.5V by the device s typical full-scale value of V SENSE. Note 4: Negative V SENSE applies to MAX481 only. Note 5: V SENSE is: MAX48F, 1mV to 1mV MAX48T, 1mV to 25mV MAX48S, 1mV to 1mV MAX481F, -5mV to +5mV MAX481T, -125mV to +125mV MAX481S, -5mV to +5mV Note 6: V OS is extrapolated from the gain accuracy test for the MAX48 and measured as (V - V REF )/AV at V SENSE = V, for the MAX481. Note 7: V SENSE is: MAX48F, 5mV MAX48T, 125mV MAX48S, 5mV MAX481F/T/S, V V REF1B = V REF1A = 2.5V Note 8: Output voltage is internally clamped not to exceed 18V. Note 9: Output settles to within 1% of final value. Note 1: The device will not experience phase reversal when overdriven. khz µs www.maximintegrated.com Maxim Integrated 4
Typical Operating Characteristics ( = V = 48V, V SENSE = V, C LOAD = 2pF, R LOAD =, T A = +25 C, unless otherwise noted.) PERCENTAGE (%) 35 3 25 2 15 1 5 OFFSET VOLTAGE HISTOGRAM -125-1 -75-5 -25 25 5 75 1 125 OFFSET VOLTAGE (µv) MAX48 toc1 OFFSET VOLTAGE (V) 3 25 2 15 1 5-5 -1-15 -2 OFFSET VOLTAGE vs. TEMPERATURE -25-3 -5-25 25 5 75 1 125 15 TEMPERATURE ( C) MAX48 toc2 GAIN ACCURACY (%) GAIN ACCURACY vs. TEMPERATURE.5.4.3.2.1 -.1 -.2 -.3 -.4 -.5-5 -25 25 5 75 1 125 TEMPERATURE ( C) MAX48 toc3 GAIN ACCURACY (%) REFERENCE REJECTION RATIO (db) -.5 -.1 -.15-1 -2-3 -4-5 -6-7 -8-9 -1-11 -12 V = 48V GAIN ACCURACY vs. S VERSION T VERSION F VERSION -.2 4 16 28 4 52 64 76 (V) MAX481F/T/S REFERENCE REJECTION RATIO vs. FREQUENCY 1 1 1 1k 1k 1k FREQUENCY (Hz) MAX48 toc4 MAX48 toc7 COMMON-MODE REJECTION RATIO (db) GAIN (db) -1-2 -3-4 -5-6 -7-8 -9-1 -11-12 -13 5 45 4 35 3 25 2 15 1 5 MAX481F/T/S COMMON-MODE REJECTION RATIO vs. FREQUENCY 1 1 1 1k 1k 1k 1M MAX48F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY V SENSE = 1mV FREQUENCY (Hz) MAX48S MAX48T MAX48F.1 1 1 1 1 FREQUENCY (khz) MAX48 toc5 MAX48 toc8 POWER-SUPPLY REJECTION RATIO (db) GAIN (db) -1-2 -3-4 -5-6 -7-8 -9-1 -11-12 -13 5 45 4 35 3 25 2 15 1 5 MAX481F/T/S POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 1 1 1 1k 1k 1k 1M MAX481F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY V = 1mV P-P FREQUENCY (Hz) MAX481S MAX481T MAX481F.1 1 1 1 1 FREQUENCY (khz) MAX48 toc6 MAX48 toc9 www.maximintegrated.com Maxim Integrated 5
Typical Operating Characteristics (continued) ( = V = 48V, V SENSE = V, C LOAD = 2pF, R LOAD =, T A = +25 C, unless otherwise noted.) SUPPLY CURRENT (µa) 85 8 75 7 65 MAX48 SUPPLY CURRENT vs. NO LOAD V SENSE = V MAX48 toc1 SUPPLY CURRENT (µa) 125 12 115 11 15 1 95 9 MAX481 SUPPLY CURRENT vs. V REF = 2.5V NO LOAD V SENSE = V MAX48 toc11 SUPPLY CURRENT (µa) 115 11 15 1 95 9 85 8 75 7 MAX48 SUPPLY CURRENT vs. TEMPERATURE MAX48 toc12 6 4 16 28 4 52 64 76 (V) 85 4 16 28 4 52 64 76 (V) 65-5 -25 25 5 75 1 125 TEMPERATURE ( C) SUPPLY CURRENT (µa) MAX481 SUPPLY CURRENT vs. TEMPERATURE 115 V REF1A = V REF1B = 2.5V 11 15 1 95 9 85 8 75 7 65-5 -25 25 5 75 1 125 TEMPERATURE ( C) MAX48 toc13 V HIGH VOLTAGE (VCC - VOH) (V).5.45.4.35.3.25.2.15.1.5 = 4.5V T A = +25 C V HIGH VOLTAGE vs. I (SOURCING) T A = +85 C T A = C.1.2.3.4.5.6.7.8.9 1. I (SOURCING) (ma) T A = +125 C T A = -4 C MAX48 toc14 V LOW VOLTAGE (mv) 3 25 2 15 1 5 = 4.5V V LOW VOLTAGE vs. I (SINKING) T A = +25 C T A = +85 C T A = +125 C 5 1 15 2 25 3 35 4 45 5 I (SINKING) (µa) T A = C T A = -4 C MAX48 toc15 MAX48F SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc16 MAX48T SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc17 MAX48S SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc18 5mV/div 5mV/div 5mV/div 25mV/div 1mV/div 3mV/div www.maximintegrated.com Maxim Integrated 6
Typical Operating Characteristics (continued) ( = V = 48V, V SENSE = V, C LOAD = 2pF, R LOAD =, T A = +25 C, unless otherwise noted.) MAX481F SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc19 MAX481T SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc2 MAX481S SMALL-SIGNAL TRANSIENT RESPONSE MAX48 toc21 1mV/div 2.5mV/div 1mV/div 5mV/div 5mV/div 5mV/div MAX48F LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc22 MAX48T LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc23 MAX48S LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc24 4mV/div 1mV/div 33mV/div 2V/div 2V/div 2V/div MAX481F LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc25 MAX481T LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc26 MAX481S LARGE-SIGNAL TRANSIENT RESPONSE MAX48 toc27 4mV/div 1mV/div 33mV/div 2V/div 2V/div 2V/div www.maximintegrated.com Maxim Integrated 7
Typical Operating Characteristics (continued) ( = V = 48V, V SENSE = V, C LOAD = 2pF, R LOAD =, T A = +25 C, unless otherwise noted.) -TRANSIENT RESPONSE MAX48 toc28 MAX48F SATURATION RECOVERY RESPONSE ( = 4.5V) MAX48 toc29 MAX48T STARTUP DELAY (V SENSE = 25mV) MAX48 toc3 V = 2V = 4V = 2V STEP V REF1 = V REF2 = 2.5V = 2V 5V/div 5mV/div ( TO 1V) 5V/div V 1V/div 2V/div 2.5V/div 4µs/div 1µs/div www.maximintegrated.com Maxim Integrated 8
Pin Description MAX48 PIN MAX481 NAME FUNCTION 1 1 Power connection to the external-sense resistor. 2 2 Supply Voltage Input. Decouple to with at least a.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 Ground 5 5 Voltage Output. For the unidirectional MAX48, V is proportional to V SENSE. For the bidirectional MAX481, the difference voltage (V - V REF ) is proportional to V SENSE and indicates the correct polarity. 8 8 Load connection to the external sense resistor. 6 REF1B Reference Voltage Input: Connect REF1B to REF1A or to (see the External Reference section). 7 REF1A Reference Voltage Input: Connect REF1A and REF1B to a fixed reference voltage (V REF ). V is equal to V REF when V SENSE is zero (see the External Reference section). Detailed Description The MAX48/MAX481 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 ( ). The MAX48/MAX481 monitors current through a current-sense resistor and amplifies the voltage across the resistor. The MAX48 senses current unidirectionally, while the MAX481 senses current bidirectionally. The 76V input voltage range of the MAX48/MAX481 applies independently to both supply voltage ( ) and common-mode, input-sense voltage (V ). High-side current monitoring does not interfere with the ground path of the load being measured, making the MAX48/ MAX481 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 MAX481 charging current is represented by an output voltage from V REF to, while discharge current is given from V REF to. Measurements of with respect to V REF yield a positive and negative voltage during charge and discharge, as illustrated in Figure 1 for the MAX481T. Current Monitoring The MAX48 operates as follows: current from the source flows through R SENSE to the load (Figure 2), creating a sense voltage, V SENSE. 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 V SOURCE - (I LOAD )(R SENSE ). The amplifier s open-loop gain forces its noninverting input to the same voltage as the inverting input. Therefore, the drop across RG1 equals V SENSE. The internal current mirror multiplies I RG1 by a current gain factor, β, to give I A2 = 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 MAX48F, 2V/V for the MAX48T, and 6V/V for the MAX48S. The MAX481 input stage differs slightly from the MAX48 (Figure 3). Its topology allows for monitoring of bidirectional currents through the sense resistor. When current flows from to, the MAX481 matches the voltage drop across the external sense resistor, R SENSE, 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 MAX481, the output signal of amplifier A2 is level- shifted to the reference voltage (V REF = V REF1A = V REF1B ), resulting in a voltage at the output pin () www.maximintegrated.com Maxim Integrated 9
1V 4.5V TO 76V BATTERY I LOAD V SENSE R SENSE I CHARGE SYSTEM LOAD AND CHARGER 5V V - VREF CHARGE CURRENT V = 1V V SENSE MAX481T REF1A 5V -25mV 25mV REF1B V = V -5V DISCHARGE CURRENT V REF1A = V REF1B = 5V Figure 1. MAX481T Transfer Curve V SENSE I LOAD V SENSE R SENSE R G1 R G2 MAX481 R G1 R G2 MAX48 A1 RF A1 Q1 Q2 A2 Q1 CURRENT MIRROR I A2 A2 A3 CURRENT MIRROR CURRENT MIRROR 125kΩ 125kΩ REF1B REF1A V REF Figure 2. MAX48 Functional Diagram Figure 3. MAX481 Functional Diagram that swings above V REF voltage for positive-sense voltages and below V REF for negative-sense voltages. V is equal to V REF when V SENSE is equal to zero. Note: For Gain = 5 (F), R G1 = R G2 = 16k. For Gain = 2 (T), R G1 = R G2 = 6k. For Gain = 6 (S), R G1 = R G2 = 2k. Set the full-scale output range by selecting R SENSE and the appropriate gain version of the MAX48/ MAX481. www.maximintegrated.com Maxim Integrated 1
Table 1. Typical Component Values FULL-SCALE LOAD CURRENT, ILOAD (A) CURRENT-SENSE RESISTOR (mw) GAIN (V/V) FULL-SCALE VSENSE (mv) MAX481 FULL-SCALE VOLTAGE (V - VREF, V).5 1 5 ±5 ±2.5.125 1 2 ±125 ±2.5.5 1 6 ±5 ±3. 5. 1 5 ±5 ±2.5 1.25 1 2 ±125 ±2.5.5 1 6 ±5 ±3. 5. 1 5 ±5 ±2.5 12.5 1 2 ±125 ±2.5 5. 1 6 ±5 ±3. FULL-SCALE LOAD CURRENT, ILOAD (A) CURRENT-SENSE RESISTOR (mw) GAIN (V/V) FULL-SCALE VSENSE (mv) MAX48 FULL-SCALE VOLTAGE (V) 1. 1 5 1 5..25 1 2 25 5..1 1 6 1 6. 1. 1 5 1 5. 2.5 1 2 25 5. 1. 1 6 1 6. 5. 1 5 5 2.5 25. 1 2 25 5. 1. 1 6 1 6. External References (MAX481) For the bidirectional MAX481, the V reference level is controlled by REF1A and REF1B. V REF is defined as the average voltage of V REF1A and V REF1B. Connect REF1A and REF1B to a low-noise, regulated voltage source to set the output reference level. In this mode, V equals V REF1A when V SENSE 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 (V REF ) is equal to V REF1A divided by two. V equals V REF1A /2 when V SENSE equals zero. In either mode, the output swings above the reference voltage for positive current-sensing (V > V ). The output swings below the reference voltage for negative current-sensing (V < V ). Applications Information Recommended Component Values Ideally, the maximum load current develops the full-scale sense voltage across the current-sense resistor. Choose the gain needed to yield the maximum output voltage required for the application: V = V SENSE 5 A V where V SENSE is the full-scale sense voltage, 1mV for gain of 5V/V, 25mV for gain of 2V/V, 1mV for gain of 6V/V, and A V is the gain of the device. In applications monitoring a high current, ensure that R SENSE 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 MAX48/MAX481 sense a wide variety of currents with different sense-resistor values. Table 1 lists common resistor values for typical operation. www.maximintegrated.com Maxim Integrated 11
I LOAD = I LOAD = LOAD R SENSE R SENSE LOAD REF1A MAX481 5V REF1A MAX481 1V REF1B REF1B 5V 5V Figure 4. MAX481 Reference Inputs The full-scale output voltage is V = R SENSE I LOAD (MAX) A V, for the MAX48 and V = V REF ± R SENSE I LOAD(MAX) A V for the MAX481. V SENSE(MAX) is 1mV for the 5V/V gain version, 25mV for the 2V/V gain version, and 1mV for the 6V/V gain version. Choosing the Sense Resistor Choose R SENSE 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 R SENSE value. Accuracy: A high R SENSE 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 R SENSE to provide approximately 1mV (gain of 5V/V), 25mV (gain of 2V/V), or 1mV (gain of 6V/V) of sense voltage for the full-scale current in each application. Efficiency and Power Dissipation: At high current levels, the I2R losses in R SENSE 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 I SENSE 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 around a core, as in metal-film or wire-wound resistors, they are a straight band of metal and are available in values under 1Ω. Because of the high currents that flow through R SENSE, take care to eliminate parasitic trace resistance from causing errors in the sense voltage. Either use a four-terminal current-sense resistor or use Kelvin (force and sense) PC board layout techniques. Dynamic Range Consideration Although the MAX481 have fully symmetrical bidirectional V SENSE input capability, the output voltage range is usually higher from REF to and lower from REF to (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. Power-Supply Bypassing and Grounding For most applications, bypass to with a.1µf ceramic capacitor. In many applications, can be connected to one of the current monitor terminals ( or ). Because is independent of the monitored voltage, can be connected to a separate regulated supply. If will be subject to fast-line transients, a series resistor can be added to the power-supply line of the MAX48/MAX481 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.1µf bypass capacitor work well. The MAX48/MAX481 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. www.maximintegrated.com Maxim Integrated 12
Power Management The bidirectional capability of the MAX481 makes it an excellent candidate for use in smart battery packs. In the application diagram (Figure 5), the MAX481 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. Typical Operating Circuit SYSTEM LOAD R SENSE I SENSE = 4.5V TO 76V R SENSE MAX48 SYSTEM POWER MANAGEMENT AND CHARGER CIRCUITRY SERIAL INTERFACE Figure 5. MAX481 Used In Smart-Battery Application Selector Guide MAX481 REF1A MAX1243 ADC µc REF1B PART GAIN (V/V) ISENSE MAX48FAUA 5 Unidirectional MAX48FASA 5 Unidirectional MAX48TAUA 2 Unidirectional MAX48TASA 2 Unidirectional MAX48SAUA 6 Unidirectional MAX48SASA 6 Unidirectional MAX481FAUA 5 Bidirectional MAX481FASA 5 Bidirectional MAX481TAUA 2 Bidirectional MAX481TASA 2 Bidirectional MAX481SAUA 6 Bidirectional MAX481SASA 6 Bidirectional 1.8V BATTERY Chip Information PROCESS: Bipolar Ordering Information (continued) PART TEMP RANGE PIN-PACKAGE MAX48TASA+ -4 C to +125 C 8 SO MAX48SAUA+ -4 C to +125 C 8 µmax MAX48SAUA/V+ -4 C to +125 C 8 µmax MAX48SASA+ -4 C to +125 C 8 SO MAX481FAUA+ -4 C to +125 C 8 µmax MAX481FASA+ -4 C to +125 C 8 SO MAX481TAUA+ -4 C to +125 C 8 µmax MAX481TASA+ -4 C to +125 C 8 SO MAX481SAUA+ -4 C to +125 C 8 µmax MAX481SASA+ -4 C to +125 C 8 SO +Denotes a lead(pb)-free/rohs-compliant package. Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 LINE NO. LAND PATTERN NO. 8 µmax U8+1 21-36 9-92 8 SO S8+2 21-41 9-96 www.maximintegrated.com Maxim Integrated 13
Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 1/2 Initial release 1 11/8 Added values for RG1 and RG2 1 2 5/9 Added lead-free and automotive parts to Ordering Information 1 3 5/1 Removed automotive part and added soldering temperature 1, 2 4 7/11 Added automotive part designation 1 5 5/15 Updated Benefits and Features section 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated s website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated 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 and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. 215 Maxim Integrated Products, Inc. 14