Bidirectional, High-Side, Current-Sense Amplifiers with Reference

Transcription

1 9-2423; Rev 2; /3 Bidirectional, High-Side, Current-Sense General Description The 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 µa supply current (which drops to only µa in shutdown), and a total output error of less than.5%. The wide.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 5V/V or V/V. A single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX47 contains an internal 2.5V reference. The charging current is represented by an output voltage from 2.5V to V CC, while discharge current is given from 2.5V to GND. The MAX47 is similar, but with a reference voltage of.5v. The MAX469 has an adjustable reference voltage, set by two external resistors. The MAX472 has an input for an external reference. The MAX469/MAX47/MAX472 operate from a 2.7V to 24V single supply. The MAX47 operates from a 3.6V to 24V single supply. All devices are specified over the automotive operating temperature range, -4 C to +25 C. The MAX47/MAX47/MAX472 are available in 8-pin µmax and 8-pin thin QFN packages. The MAX469 is available in a -pin µmax package. Applications Notebook Fuel Gauging Smart-Battery Packs/Chargers Motor Control Power-Management Systems Cell-Phone Battery-Current Monitoring PART REFERENCE Selector Guide SUPPLY VOLTAGE RANGE (V) Pin Configurations appear at end of data sheet. COMMON- MODE RANGE (V) MAX469 ADJUSTABLE 2.7 to to 24 MAX47 2.5V 3.6 to to 24 MAX47.5V 2.7 to to 24 MAX472 EXTERNAL 2.7 to to 24 Features Bidirectional, Compact, Current-Sense Solution Total Output Error Less than.5% Selectable Gain of 5V/V or V/V Wide.35V to 24V Common-Mode Range Independent of Supply Voltage 2.7V to 24V Single-Supply Operation Internal Precision Reference Adjustable (MAX469) 2.5V (MAX47).5V (MAX47) Low µa Supply Current µa Supply Current in Shutdown Available in Space-Saving Packages 8-Pin Thin QFN (MAX47/MAX47/MAX472) 8-Pin µmax (MAX47/MAX47MAX472) -Pin µmax (MAX469) V BATT =.35V TO 24V V CC = 3.6V TO 24V Ordering Information PART TEMP RANGE PIN-PACKAGE TOP MARK MAX469AUB -4 C to +25 C µmax MAX47AUA -4 C to +25 C 8 µmax MAX47ATA -4 C to +25 C 8 Thin QFN-EP* ABN MAX47AUA -4 C to +25 C 8 µmax MAX47ATA -4 C to +25 C 8 Thin QFN-EP* ABO MAX472AUA -4 C to +25 C 8 µmax MAX472ATA -4 C to +25 C 8 Thin QFN-EP* ABP *EP = Exposed paddle. Typical Operating Circuit V CC GSEL SHDN RS- R SENSE MAX47 GND FROM BATTERY CHARGER RS+ OUT REFOUT LOAD TO ADC 2.5V Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS V CC, RS+, RS- to GND...-.3V to +26V OUT to GND...-.3V to Lesser of (V CC +.3V) or 5V Differential Input Voltage (V RS+ - V RS- )...±.3V GSEL, SHDN, REFOUT, REFIN and ADJ to GND...-.3V to (V CC +.3V) OUT Short-Circuit Duration to GND or to Lesser of (V CC or 5V)...Continuous REFOUT Short Circuit to V CC or GND...Continuous Current into Any Pin...±2mA 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 Continuous Power Dissipation (T A = +7 C) 8-Pin µmax (derate 4.5 mw/ C above +7 C)...362mW 8-Pin Thin QFN (derate 24.4mW/ C above +7 C)...95mW -Pin µmax (derate 5.6 mw/ C above +7 C) mW Operating Temperature Range...-4 C to +25 C Junction Temperature...+5 C Storage Temperature Range C to +5 C Lead Temperature (soldering, s)...+3 C (V RS+ = V RS- = V CC = 2.7V to 24V, V SENSE = V RS+ - V RS- = V, I REFOUT =, V SHDN = V CC, V GSEL = GND, V REFIN = 2.5V (MAX472), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C and at V CC = V RS+ = 2V.) (Notes, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Operating Voltage Range (Note 3) Input-Referred Offset Voltage (Note 5) MAX469/MAX47/MAX472 (Note 4) V CC MAX V OS V CC = V RS+ = V RS- = 2V T A = +25 C.8.25 T A = -4 C to +85 C.8 T A = T MIN to T MAX Common-Mode Input Range CMVR Guaranteed by CMRR test V Common-Mode Rejection Ratio CMRR.35V V RS+ = V RS- 24V, V CC = 2V 2 db Supply Current I CC V CC = V RS+ = V RS- = 24V, R L = open, T A = T MIN to T MAX 25 µa V CC = V RS+ = V RS- = 5.5V, SHDN = GND, T A = +25 C Shutdown Supply Current I CC SHDN V CC = V RS+ = V RS- = 24V, SHDN = GND 9 3 Leakage Current V RS+ = V RS- = 24V, V CC = V..5 µa Input Bias Current I RS+, I RS- V CC = V RS+ = V RS- = 24V µa Recommended Full-Scale Sense Voltage (Note 6) Gain = 5V/V 75 V SENSE Gain = V/V 5 V mv µa mv 2

3 ELECTRICAL CHARACTERISTICS (continued) (V RS+ = V RS- = V CC = 2.7V to 24V, V SENSE = V RS+ - V RS- = V, I REFOUT =, V SHDN = V CC, V GSEL = GND, V REFIN = 2.5V (MAX472), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C and at V CC = V RS+ = 2V.) (Notes, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Total OUT Voltage Error (Note 7) V SENSE = 75mV, T A = +25 C ±.25 ±. V CC = V RS+ = 2V, T A = - 4 C to + 85 C ±.5 gain = 5 T A = T MIN to T MAX ±2. V SENSE = 5mV, T A = +25 C ±.25 ±. V CC = V RS+ = 2V, T A = - 4 C to + 85 C ±.5 gain = T A = T MIN to T MAX ±2.5 MAX469/MAX47/ MAX472: T A = +25 C ±.4 ±. V SENSE = -35mV, V CC = V RS+ = 2V, gain = 5 T A = - 4 C to + 85 C T A = T MIN to T MAX ±2. ±3. MAX469/MAX47/ T A = +25 C ±.8 ±2. MAX472: V SENSE = -7.5mV, V CC = V RS+ = 2V, gain = T A = - 4 C to + 85 C T A = T MIN to T MAX ±4. ±6 % MAX47: T A = +25 C ±. ±2.5 V SENSE = -5mV, V CC = V RS+ = 2V, T A = - 4 C to + 85 C ±4. gain = 5 T A = T MIN to T MAX ±6. MAX47: T A = +25 C ±2. ±5 V SENSE = -7.5mV, V CC = V RS+ = 2V, T A = - 4 C to + 85 C ± gain = T A = T MIN to T MAX ±5 V SENSE = 3mV, V C C = 2V, V RS + = 2V T A = +25 C ±3 3

4 ELECTRICAL CHARACTERISTICS (continued) (V RS+ = V RS- = V CC = 2.7V to 24V, V SENSE = V RS+ - V RS- = V, I REFOUT =, V SHDN = V CC, V GSEL = GND, V REFIN = 2.5V (MAX472), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C and at V CC = V RS+ = 2V.) (Notes, 2) OUT Voltage High OUT Voltage Low PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V CC - V OH V OL I OUT = µa, V SENSE = mv, V RS+ = V CC I OUT = 5µA, V SENSE = mv, V RS+ = V CC I OUT = -µa, V SENSE = -mv, V RS+ = V CC I OUT = -5µA, V SENSE = -mv, V RS+ = V CC MAX47, V CC = 2.7V MAX469/MAX47/ MAX472, V CC = 3.6V MAX47, V CC = 2.7V MAX469/MAX47/ MAX472, V CC = 3.6V MAX47, V CC = 2.7V MAX469/MAX47/ MAX472, V CC = 3.6V MAX47, V CC = 2.7V MAX469/MAX47/ MAX472, V CC = 3.6V mv mv -3dB Bandwidth BW V SENSE = 5mV, Gain = 5V/V V CC = 2V, C L = pf Gain = V/V 4 GSEL = GND 5 Gain A V GSEL = V CC khz V/V Capacitive-Load Stability pf Power-Supply Rejection Ratio PSRR V CC = 2.7V to 24V (MAX469/MAX47/MAX472), V CC = 3.6V to 24V (MAX47) 2 db Logic Low Voltage (GSEL, SHDN) V IL V CC = 3.6V or 24V.6 V Logic High Voltage (GSEL, SHDN) V IH V CC = 3.6V or 24V 2 V Gain-Select Input Current I GSEL GSEL = V CC = 24V or GND. µa SHDN = V CC = 24V 3 2 Shutdown Input Current I SHDN SHDN = GND, V CC = 24V. µa 4

5 ELECTRICAL CHARACTERISTICS (continued) (V RS+ = V RS- = V CC = 2.7V to 24V, V SENSE = V RS+ - V RS- = V, I REFOUT =, V SHDN = V CC, V GSEL = GND, V REFIN = 2.5V (MAX472), T A = T MIN to T MAX, unless otherwise noted. Typical values are at T A = +25 C and at V CC = V RS+ = 2V.) (Notes, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS REFOUT (MAX469/MAX47/MAX47) Reference Output Voltage Reference Output Voltage Temperature Coefficient Load Regulation V REF TCV REF MAX469, T A = +25 C V CC = 2V (Note 2) T A = T MIN to T MAX MAX47, T A = +25 C V CC = 2V T A = T MIN to T MAX MAX47, T A = +25 C V CC = 2V T A = T MIN to T MAX V CC = 2V -4 C T A +85 C 5 T A = T MIN to T MAX 2 V REFOUT I REFOUT = to 5µA 2 / I REF IREFOUT = to -µa 4 V ppm/ C mv/ma Line Regulation V REF/ V CC 2.7V V CC 24V 2 µv/v REF Capacitive-Load Stability 5 pf Reference Adjust Voltage Threshold Reference Output Voltage Range V ADJ MAX469, V CC = 2V.23 V MAX469, range adjustable with R and R2, V CC = 2V V ADJ to +4 Reference Adjust Input Current I ADJ MAX469, V CC = 2V, V ADJ =.23V na REFIN (MAX472 only) Input-Voltage Range V CC = 2V 4 V Input Current REFIN = 2.5V, V CC = 2V µa Note : All devices are % tested at T A = +25 C. Limits over temperature are guaranteed by design. Note 2: R = 25kΩ, R2 = 2kΩ for the MAX469 only (see Functional Diagram). This sets REFOUT to 2.49V nominal. Note 3: Guaranteed by the PSRR test. Note 4: The REFOUT voltage for the MAX469 should be set such that it does not exceed V CC -.V. Similarly, the maximum REFIN voltage for the MAX472 should also be less than V CC -.V. Note 5: Input-Referred Offset Voltage is defined as the voltage difference between OUT and REFOUT, divided by the selected gain of either 5 or, when V SENSE = V RS+ - V RS- = V. Note 6: The negative full-scale sense voltage is limited by the voltage range of OUT from V REFOUT 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). V 5

6 Typical Operating Characteristics (V CC = V RS+ = 2V, V SENSE = 5mV for gain of V/V and 75mV for gain of 5V/V, T A = +25 C, unless otherwise noted.) PERCENTAGE OF UNITS (%) TOTAL ERROR (%) INPUT OFFSET VOLTAGE DISTRIBUTION TOTAL ERROR vs. SUPPLY VOLTAGE V SENSE = 75mV A V = 5V/V V OS (µv) V SENSE = 5mV A V = V/V SUPPLY VOLTAGE (V) MAX toc MAX toc4 INPUT OFFSET VOLTAGE (µv) TOTAL ERROR (%) INPUT OFFSET VOLTAGE vs. TEMPERATURE 5 A 25 V = V/V TEMPERATURE ( C) TOTAL ERROR vs. SUPPLY VOLTAGE (V SENSE = 3mV) A V = V/V -.5 A V = 5V/V SUPPLY VOLTAGE (V) MAX toc2 MAX toc5 (VOUT - VREF) (V) TOTAL ERROR (%) A V = V/V (V OUT - V REF ) vs. V SENSE TOTAL ERROR vs. TEMPERATURE V SENSE = 5mV A V = V/V V CC = 2V A V = 5V/V V SENSE (V) V CC = 24V TEMPERATURE ( C) MAX toc3 MAX toc6 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. SUPPLY VOLTAGE A V = V/V MAX47 MAX47 MAX469 MAX472 MAX toc7 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. TEMPERATURE A V = 5V/V V CC = 24V V CC = 2V MAX toc8 REFOUT (V) MAX469 REFOUT vs. TEMPERATURE REFOUT CONNECTED TO ADJ MAX toc SUPPLY VOLTAGE (V) TEMPERATURE ( C) TEMPERATURE ( C) 6

7 Typical Operating Characteristics (continued) (V CC = V RS+ = 2V, V SENSE = 5mV for gain of V/V and 75mV for gain of 5V/V, T A = +25 C, unless otherwise noted.) REFOUT (V) MAX47 REFOUT vs. TEMPERATURE TEMPERATURE ( C) MAX toc REFOUT (V) MAX47 REFOUT vs. TEMPERATURE TEMPERATURE ( C) MAX toc REFOUT (V) MAX469 REFOUT vs. SUPPLY VOLTAGE SUPPLY VOLTAGE (V) MAX toc2 REFOUT (V) MAX47 REFOUT vs. SUPPLY VOLTAGE MAX toc3 REFOUT (V) MAX47 REFOUT vs. SUPPLY VOLTAGE MAX toc4 VOH (mv) V OH vs. TEMPERATURE V OH = V CC - V OUT I L = 5µA MAX toc I L = µa SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) TEMPERATURE ( C) VOL (mv) V OL vs. TEMPERATURE I L = 5µA I L = µa MAX toc6 GAIN (db) SMALL-SIGNAL GAIN vs. FREQUENCY A V = 5V/V A V = V/V MAX toc7 PSRR AND CMRR (db) PSRR AND CMRR vs. FREQUENCY CMRR PSRR MAX toc TEMPERATURE ( C) -2. FREQUENCY (khz) -4.. FREQUENCY (Hz) 7

8 Typical Operating Characteristics (continued) (V CC = V RS+ = 2V, V SENSE = 5mV for gain of V/V and 75mV for gain of 5V/V, T A = +25 C, unless otherwise noted.) SMALL-SIGNAL TRANSIENT RESPONSE µs/div MAX toc9 GAIN = 5 INPUT 5mV/div OUTPUT 2mV/div REF SMALL-SIGNAL TRANSIENT RESPONSE µs/div MAX toc2 GAIN = INPUT 5mV/div OUTPUT 5mV/div REF LARGE-SIGNAL TRANSIENT RESPONSE µs/div MAX toc2 GAIN = 5 INPUT 5mV/div OUTPUT 2V/div REF LARGE-SIGNAL TRANSIENT RESPONSE MAX toc22 STARTUP DELAY MAX toc23 EXITING SHUTDOWN MAX toc24 GAIN = INPUT 2mV/div V CC V/div V OUT 5V/div V SHDN 5V/div V OUT 2V/div OUTPUT 2V/div REF V REFOUT 5V/div V REFOUT 2V/div µs/div 2µs/div µs/div 8

9 MAX469 PIN MAX47/ MAX47 MAX472 NAME FUNCTION Pin Description SHDN Shutdown Input. Drive SHDN low to select shutdown mode. Connect SHDN to V CC for normal operation RS- Negative Connection to the External Sense Resistor RS+ Positive Connection to the External Sense Resistor 4 N.C. No Connection. Not internally connected GND 6 ADJ 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 (MAX469 only, see Functional Diagram). 7 5 REFOUT Reference Output Voltage (MAX469/MAX47/MAX47) OUT Voltage Output. The difference voltage, V OUT - V REF, is proportional to the voltage difference between RS+ and RS- and indicates the correct polarity V CC Supply Voltage Input. Bypass V CC to GND with a.µf capacitor. 8 8 GSEL Gain-Setting Input. Connect GSEL low to select gain = 5V/V, or connect GSEL high to select gain = V/V. 5 REFIN Reference Input Voltage (MAX472) Functional Diagram LOAD 2.7V TO 24V FROM BATTERY CHARGER R SENSE RS+ RS- V CC CSA MAX469 OUT TO ADC GAIN SELECT GSEL SHUTDOWN SHDN V REF.23V OA REFOUT ADJ R GND R2 9

10 Detailed Description The bidirectional, high-side, current-sense amplifiers are ideal for portable equipment. The wide.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 MAX469/MAX47/MAX472 operate from a 2.7V to 24V single supply. Because the MAX47 has a 2.5V internal reference, it operates from 3.6V to 24V. All devices have a low µa supply current that reduces to only µa (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 5V/V or V/V. Drive GSEL low to select gain of 5V/V or drive GSEL high to choose gain of V/V (see Functional Diagram). The MAX469 has an adjustable reference voltage set by two external resistors between REFOUT and ADJ, and GND pins. The MAX47 contains an internal 2.5V reference. The MAX47 is similar to the MAX47 but with a fixed internal reference voltage of.5v. The MAX472 has a reference input pin to allow use of external references. Charging current is represented by an output voltage from the reference voltage to V CC, while discharge current is given from the reference voltage to GND. The direction of V SENSE is totally arbitrary. The input stage of the is shown in Figure. Its unique topology allows for monitoring bidirectional currents through the sense resistor (R SENSE ). If, for instance, current flows from RS+ to RS-, the match for the voltage drop over the external sense resistor (R SENSE ) by increasing the current through the internal Q and RG. At the same time, the current through Q2 and RG2 decreases, however, internal circuitry not shown in Figure prevents Q2 from turning off completely. Likewise, if current flows from RSto RS+, the current through Q2 and RG2 increases and the current through Q decreases. In this way, the voltages at the input terminals of the internal amplifier A are kept constant and an accurate measurement of the sense voltage is achieved. In the following amplifier stages of the, the output signal of amplifier A2 is level-shifted towards the reference voltage (V REF ), resulting in a voltage at the output pin (OUT) that swings above the V REF voltage for positive-sense voltages and below V REF for negative-sense voltages. Q RS+ RG R SENSE A Figure. Detailed Input Stage RS- 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 used as a bidirectional current monitor. In Figure 2, the direction of V SENSE 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 can achieve high-current measurements by using low-value sense resistors, which can be paralleled to further increase the currentsense limit. Adjusting V REF (MAX469) The MAX469 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,.23v (typ). The maximum voltage for REFOUT is 4V (that requires V CC 5.V). The recommended range for the external resistors is: R + R2 should be > 2kΩ and < 5kΩ. RG2 Q2 OUT A2 I OUT

11 2 CELLS I DISCHARGE R SENSE I CHARGE RS- RS+ V CC MAX47 GSEL OUT SHDN REFOUT GND LOAD TO ADC 2.5V V OUT - V REF -25mV 25mV 5mV V SENSE DISCHARGE CURRENT 5V 2.5V -2.5V A V = CHARGE CURRENT Figure 2. Bidirectional Current Monitor External Reference (MAX472) The MAX472 contains REFIN pin for external reference voltage. The allowable voltage range on REFIN is V (min) to 4V (max) with V CC 5.V. Reference Output (MAX469/MAX46/MAX47) The REFOUT of the MAX469/MAX47/MAX47 can sink µa and source 5µA. Keep the total capacitance on REFOUT under 5pF to maintain stability. 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: V OUT = V SENSE x A V where V SENSE is the full-scale sense voltage, 75mV for gain of 5V/V, or 5mV for gain of V/V. A V is the gain of the device. In applications monitoring high current, ensure that R SENSE is able to dissipate its own I 2 R 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. The sense a wide variety of currents with different sense-resistor values. Table lists common resistor values for typical operation of these devices. Listed output voltage is with respect to REF. Sense Resistor, R SENSE Choose R SENSE based on the following criteria: Voltage Loss: A high R SENSE value causes the powersource 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 because offsets become less significant when the sense voltage is larger. For best performance, select R SENSE to provide approximately 75mV (gain of 5V/V) or 5mV (gain of V/V) of sense voltage for the full-scale current in each application. Efficiency and Power Dissipation: At high-current levels, the I 2 R 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 round a

12 Table. Recommended Component Values FULL-SCALE CURRENT (A) CURRENT-SENSE RESISTOR (mω) GAIN (V/V) V SENSE (mv) FULL-SCALE OUTPUT VOLTAGE WITH RESPECT TO REF (V) core, as in metal-film or wire-wound resistors, they are a straight band of metal and are available in values under Ω. Peak Current: The maximum current through R SENSE must be limited to: I PEAK =.3V / (R SENSE + R TRACE ) where R TRACE is the total stray resistance from RS+ and RS- to R SENSE. To prevent forwarding the back-toback diodes between the differential input, the absolute maximum of the differential input voltage is.3v. Dynamic Range Considerations Although the have fully symmetrical, bidirectional, V SENSE input capability, the outputvoltage range is usually higher from REF to V CC 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 are shut down and consume only µa. In shutdown mode, OUT is high impedance and turns off. Connect SHDN to V CC for normal operation. Power-Supply Bypassing and Grounding The 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 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 V OUT. Using differential measurement between V OUT 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. 2

13 TOP VIEW SHDN RS+ N.C. GND MAX469 µmax GSEL 9 V CC 8 OUT 7 REFOUT 6 ADJ 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 R SENSE reasonably higher than the values of the trace s resistance. SHDN RS- RS- RS+ GND MAX47 MAX47 MAX472 Thin QFN/µMAX (REFIN) FOR MAX472 ONLY. TRANSISTOR COUNT: 338 PROCESS: BiCMOS Pin Configurations GSEL V CC OUT REFOUT (REFIN) Chip Information 3

14 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 6, 8, &L, QFN THIN.EPS PACKAGE OUTLINE, 6, 8 & L, QFN THIN (DUAL), EXPOSED PAD, 3x3x.8 mm 2-37 C COMMON DIMENSIONS SYMBOL MIN. MAX. A.7.8 D E A..5 L.2.4 k.25 MIN A2.2 REF. PACKAGE VARIATIONS PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-] x e T ±. 2.3±..95 BSC MO229 / WEEA.4±.5.9 REF T ±. 2.3±..65 BSC MO229 / WEEC.3±.5.95 REF T33-.5±. 2.3±..5 BSC MO229 / WEED-3.25±.5 2. REF PACKAGE OUTLINE, 6, 8 & L, QFN THIN (DUAL), EXPOSED PAD, 3x3x.8 mm 2-37 C 4

15 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 8 ÿ.5±. D TOP VIEW E H 4X S BOTTOM VIEW 8 DIM A A MIN MAX BSC A2.3 b c D e E H L α S INCHES BSC MILLIMETERS MIN MAX BSC BSC 8LUMAXD.EPS A2 A A e b c L α FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L umax/usop APPROVAL DOCUMENT CONTROL NO. REV J 5

16 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 e ÿ.5±..6±. TOP VIEW 4X S H BOTTOM VIEW DIM A MIN - MAX.43 MIN - MAX. A A D D2 E E2 H L L b e c S α INCHES MILLIMETERS REF.94 REF BSC.5 BSC REF.498 REF 6 6 LUMAX.EPS D2 E2 GAGE PLANE A2 A c D b A α E L L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, L umax/usop APPROVAL DOCUMENT CONTROL NO. REV. 2-6 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, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.