19-4110; Rev 6; 1/11 KIT ATION EVALU E L B AVAILA 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Features o Ultra-Low Supply Current of 1µA (max) o Low 500µV (max) Input Offset Voltage o Low < 0.5% (max) Gain Error The MAX9938 high-side current-sense amplifier offers precision accuracy specifications of V OS less than 500μV (max) and gain error less than 0.5% (max). Quiescent supply current is an ultra-low 1μA. The MAX9938 fits in a tiny, 1mm x 1mm UCSP™ package size or a 5-pin SOT23 package, making the part ideal for applications in notebook computers, cell phones, PDAs, and all battery-operated portable devices where accuracy, low quiescent current, and small size are critical. The MAX9938 features an input common-mode voltage range from 1.6V to 28V. These current-sense amplifiers have a voltage output and are offered in four gain versions: 25V/V (MAX9938T), 50V/V (MAX9938F), 100V/V (MAX9938H), and 200V/V (MAX9938W). o Input Common Mode: +1.6V to +28V o Voltage Output o Four Gain Versions Available 25V/V (MAX9938T) 50V/V (MAX9938F) 100V/V (MAX9938H) 200V/V (MAX9938W) o Tiny 1mm x 1mm x 0.6mm, 4-Bump UCSP, 5-Pin SOT23, or 2mm x 2mm x 0.8mm, 6-Pin µDFN Packages The four gain selections offer flexibility in the choice of the external current-sense resistor. The very low 500μV (max) input offset voltage allows small 25mV to 50mV full-scale VSENSE voltage for very low voltage drop at full-current measurement. The MAX9938 is offered in tiny 4-bump, UCSP (1mm x 1mm x 0.6mm footprint), 5-pin SOT23, and 6-pin μDFN (2mm x 2mm x 0.8mm) packages specified for operation over the -40°C to +85°C extended temperature range. Ordering Information PINPACKAGE PART GAIN (V/V) TOP MARK MAX9938TEBS+G45 4 UCSP 25 +AGD MAX9938FEBS+G45 4 UCSP 50 +AGE MAX9938HEBS+G45 4 UCSP 100 +AGF MAX9938WEBS+G45 4 UCSP 200 +AGI MAX9938TEUK+ 5 SOT23 25 +AFFB Cell Phones MAX9938FEUK+ 5 SOT23 50 +AFFC PDAs MAX9938HEUK+ 5 SOT23 100 +AFFD MAX9938WEUK+ 5 SOT23 200 +AFGZ MAX9938FELT+ 6 μDFN 50 +ACM Applications Power Management Systems Portable/Battery-Powered Systems +Denotes a lead(Pb)-free/RoHS-compliant package. G45 indicates protective die coating. Note: All devices are specified over the -40°C to +85°C extended temperature range. Notebook Computers UCSP is a trademark of Maxim Integrated Products, Inc. Pin Configurations TOP VIEW (BUMPS ON BOTTOM) RS+ A1 A2 RS+ 5 RS- MAX9938T/F/H/W MAX9938T/F/H/W GND B1 B2 UCSP DRAWINGS NOT TO SCALE TOP VIEW (PADS ON BOTTOM) RS4 OUT 1 N.C. 2 GND 3 MAX9938FELT 6 RS- 5 N.C. 4 RS+ OUT 1 GND 2 GND SOT23 3 OUT μDFN ________________________________________________________________ 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 MAX9938 General Description MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ABSOLUTE MAXIMUM RATINGS RS+, RS- to GND....................................................-0.3V to +30V OUT to GND .............................................................-0.3V to +6V RS+ to RS- ...........................................................................±30V Short-Circuit Duration: OUT to GND ..........................Continuous Continuous Input Current (Any Pin)..................................±20mA Continuous Power Dissipation (TA = +70°C) 4-Bump UCSP (derate 3.0mW/°C above +70°C).........238mW 5-Pin SOT23 (derate 3.9mW/°C above +70°C)............312mW 6-Pin μDFN (derate 4.5mW/°C above +70°C) .............358mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range ............................-65°C to +150°C Lead Temperature (excluding UCSP, 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. ELECTRICAL CHARACTERISTICS (VRS+ = VRS- = 3.6V, VSENSE = (VRS+ - VRS-) = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN VRS+ = 5V, TA = +25°C Supply Current (Note 2) ICC Common-Mode Input Range VCM TYP MAX 0.5 0.85 VRS+ = 5V, -40°C < TA < +85°C 1.1 VRS+ = 28V, TA = +25°C 1.1 VRS+ = 28V, -40°C < TA < +85°C Common-Mode Rejection Ratio Input Offset Voltage (Note 3) CMRR VOS G 1.6 1.6V < VRS+ < 28V, -40°C < TA < +85°C 94 TA = +25°C OUT Low Voltage OUT High Voltage Small-Signal Bandwidth (Note 5) Output Settling Time 2 ROUT 50 100 VOL VOH BW tS V/V 200 TA = +25°C ±0.1 -40°C < TA < +85°C ±0.5 ±0.6 TA = +25°C ±0.1 -40°C < TA < +85°C ±0.7 % ±0.8 MAX9938T/F/H 7.0 10 13.2 MAX9938W 14.0 20 26.4 Gain = 25 1.5 15 Gain = 50 3 30 Gain = 100 6 60 Gain = 200 12 120 VOH = VRS- - VOUT (Note 6) 0.1 0.2 VSENSE = 50mV, gain = 25 125 VSENSE = 50mV, gain = 50 60 VSENSE = 50mV, gain = 100 30 (Note 5) μV 25 MAX9938H GE V dB ±500 ±600 MAX9938F MAX9938W Output Resistance 130 ±100 MAX9938W Gain Error (Note 4) 28 -40°C < TA < +85°C MAX9938T/MAX9938F/ MAX9938H μA 2.5 Guaranteed by CMRR , -40°C < TA < +85°C MAX9938T Gain 1.8 UNITS VSENSE = 50mV, gain = 200 15 1% final value, VSENSE = 50mV 100 _______________________________________________________________________________________ kΩ mV V kHz μs 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier (VRS+ = VRS- = 3.6V, VSENSE = (VRS+ - VRS-) = 0V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design. VOUT = 0. ICC is the total current into RS+ plus RS- pins. VOS is extrapolated from measurements for the gain-error test. Gain error is calculated by applying two values of VSENSE and calculating the error of the slope vs. the ideal: Gain = 25, VSENSE is 20mV and 120mV. Gain = 50, VSENSE is 10mV and 60mV. Gain = 100, VSENSE is 5mV and 30mV. Gain = 200, VSENSE is 2.5mV and 15mV. Note 5: The device is stable for any external capacitance value. Note 6: VOH is the voltage from VRS- to VOUT with VSENSE = 3.6V/gain. Note 1: Note 2: Note 3: Note 4: Typical Operating Characteristics (VRS+ = VRS- = 3.6V, TA = +25°C, unless otherwise noted.) 20 N (%) 15 15 10 10 5 5 0 0 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 -0.4 -0.3 -0.2 -0.1 0.3 0.4 0.8 3.6V 0.6 0.4 1.8V 0 0.1 0.2 0 0.3 0.4 -40 -15 10 35 60 INPUT OFFSET VOLTAGE (mV) GAIN ERROR (%) TEMPERATURE (°C) INPUT OFFSET vs. COMMON-MODE VOLTAGE INPUT OFFSET vs. TEMPERATURE SUPPLY CURRENT vs. COMMON-MODE VOLTAGE -40 -45 -50 40 30 20 10 5 10 15 20 SUPPLY VOLTAGE (V) 25 30 1.0 0.8 0.6 0.4 0.2 0 -55 1.2 SUPPLY CURRENT (μA) 50 INPUT OFFSET (μV) -35 1.4 85 MAX9938 toc06 60 MAX9938 toc04 -30 0 28V 1.0 0.2 MAX9938 toc05 N (%) 20 1.2 MAX9938 toc03 25 SUPPLY CURRENT (μA) 25 1.4 MAX9938 toc02 30 MAX9938 toc01 30 INPUT OFFSET (μV) SUPPLY CURRENT vs. TEMPERATURE GAIN ERROR HISTOGRAM INPUT OFFSET VOLTAGE HISTOGRAM 0 -40 -15 10 35 TEMPERATURE (°C) 60 85 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 3 MAX9938 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VRS+ = VRS- = 3.6V, TA = +25°C, unless otherwise noted.) GAIN ERROR vs. TEMPERATURE -0.2 -0.3 -0.4 3.5 0.06 3.0 0.05 2.5 G = 100 VOUT (V) -0.1 4.0 MAX9938 toc08 0.07 GAIN ERROR (%) 0 0.04 1.5 0.02 1.0 0.01 0.5 0 -0.5 5 10 15 20 25 -15 10 35 60 85 0 50 TEMPERATURE (°C) VSENSE (mV) VOUT vs. VSENSE (SUPPLY = 1.6V) SMALL SIGNAL GAIN vs. FREQUENCY CMRR vs. FREQUENCY 1.4 AV = 25V/V 0 GAIN (dB) G = 100 1.0 G = 50 0.8 AV = 50V/V -10 -15 -25 40 60 80 -160 1Hz 100 G = 100 -140 -30 20 -80 -120 0.4 0 G = 50 -60 -100 -20 0.2 G = 25 -40 G = 25 0.6 -20 AV = 100V/V -5 1.2 0 MAX9938 toc12 5 MAX9938 toc10 1.6 150 100 VOLTAGE (V) 1.8 0 G = 25 0 -40 30 CMRR (dB) 0 G = 50 2.0 0.03 MAX9938 toc11 GAIN ERROR (%) 0.08 MAX9938 toc07 0.1 VOUT vs. VSENSE (SUPPLY = 3.6V) MAX9938 toc09 GAIN ERROR vs. COMMON-MODE VOLTAGE VOUT (V) MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz 1Hz 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz FREQUENCY (kHz) FREQUENCY (kHz) VSENSE (mV) SMALL-SIGNAL PULSE RESPONSE (GAIN = 50) SMALL-SIGNAL PULSE RESPONSE (GAIN = 100) MAX9938 toc13b MAX9938 toc13a 30mV 15mV VSENSE 10mV VSENSE 20mV 1.5V 1.5V VOUT 1V 20μs/div 4 VOUT 1V 25μs/div _______________________________________________________________________________________ 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier SMALL-SIGNAL PULSE RESPONSE (GAIN = 25) LARGE-SIGNAL PULSE RESPONSE (GAIN = 100) MAX9938 toc13c MAX9938 toc14a 30mV 60mV VSENSE VSENSE 10mV 40mV 1.5V 3V VOUT VOUT 1V 1V 25μs/div 20μs/div LARGE-SIGNAL PULSE RESPONSE (GAIN = 50) LARGE-SIGNAL PULSE RESPONSE (GAIN = 25) MAX9938 toc14c MAX9938 toc14b 120mV 60mV VSENSE VSENSE 10mV 20mV 3V 3V VOUT VOUT 0.5V 0.5V 25μs/div 25μs/div Pin Description PIN NAME FUNCTION UCSP SOT23 µDFN A1 5 4 RS+ External Sense Resistor Power-Side Connection A2 4 6 RS- External Sense Resistor Load-Side Connection B1 1, 2 3 GND Ground B2 3 1 OUT Output Voltage. VOUT is proportional to VSENSE = VRS+ - VRS-. — — 2, 5 N.C. No Connection. Not internally connected. _______________________________________________________________________________________ 5 MAX9938 Typical Operating Characteristics (continued) (VRS+ = VRS- = 3.6V, TA = +25°C, unless otherwise noted.) 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier MAX9938 Typical Operating Circuit ILOAD RSENSE VBATT = 1.6V TO 28V RS+ R1 RSR1 VDD = 3.3V LOAD μC P MAX9938 ROUT OUT ADC 10kΩ GND Detailed Description same value as R1 to minimize offset voltage. The current through R1 is sourced by a high-voltage p-channel FET. Its source current is the same as its drain current, which flows through a second gain resistor, ROUT. This produces an output voltage, VOUT, whose magnitude is I LOAD x R SENSE x R OUT /R 1 . The gain accuracy is based on the matching of the two gain resistors R1 and R OUT (see Table 1). Total gain = 25V/V for the MAX9938T, 50V/V for the MAX9938F, 100V/V for the MAX9938H, and 200V/V for the MAX9938W. The output is protected from input overdrive by use of an output current limiting circuit of 7mA (typical) and a 6V clamp protection circuit. The MAX9938 unidirectional high-side, current-sense amplifier features a 1.6V to 28V input common-mode range. This feature allows the monitoring of current out of a battery with a voltage as low as 1.6V. The MAX9938 monitors current through a current-sense resistor and amplifies the voltage across that resistor. The MAX9938 is a unidirectional current-sense amplifier that has a well-established history. An op amp is used to force the current through an internal gain resistor at RS+, which has a value of R1, such that its voltage drop equals the voltage drop across an external sense resistor, RSENSE. There is an internal resistor at RS- with the Table 1. Internal Gain Setting Resistors (Typical Values) 6 GAIN (V/V) R1 (Ω) ROUT (kΩ) 200 100 20 100 100 10 50 200 10 25 400 10 _______________________________________________________________________________________ 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Choosing the Sense Resistor Choose RSENSE based on the following criteria: Voltage Loss A high RSENSE value causes the power-source voltage to drop due to IR loss. For minimal voltage loss, use the lowest RSENSE value. OUT Swing vs. VRS+ and VSENSE The MAX9938 is unique since the supply voltage is the input common-mode voltage (the average voltage at RS+ and RS-). There is no separate VCC supply voltage pin. Therefore, the OUT voltage swing is limited by the minimum voltage at RS+. VOUT(max) = VRS+ (min) - VSENSE (max) - VOH and RSENSE = VOUT (max) G × I LOAD (max) VSENSE full scale should be less than VOUT/gain at the minimum RS+ voltage. For best performance with a 3.6V supply voltage, select RSENSE to provide approximately 120mV (gain of 25V/V), 60mV (gain of 50V/V), 30mV (gain of 100V/V), or 15mV (gain of 200V/V) of sense voltage for the full-scale current in each application. These can be increased by use of a higher minimum input voltage. Accuracy In the linear region (VOUT < VOUT(max)), there are two components to accuracy: input offset voltage (VOS) and gain error (GE). For the MAX9938, VOS = 500μV (max) and gain error is 0.5% (max). Use the linear equation: VOUT = (gain ± GE) x VSENSE ± (gain x VOS) to calculate total error. A high RSENSE value allows lower currents to be measured more accurately because offsets are less significant when the sense voltage is larger. 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. The precision VOS of the MAX9938 allows the use of small sense resistors to reduce power dissipation and reduce hot spots. Kelvin Connections 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) PCB layout techniques. Optional Output Filter Capacitor When designing a system that uses a sample-and-hold stage in the ADC, the sampling capacitor momentarily loads OUT and causes a drop in the output voltage. If sampling time is very short (less than a microsecond), consider using a ceramic capacitor across OUT and GND to hold VOUT constant during sampling. This also decreases the small-signal bandwidth of the currentsense amplifier and reduces noise at OUT. Input Filters Some applications of current-sense amplifiers need to measure currents accurately even in the presence of both differential and common-mode ripple, as well as a wide variety of input transient conditions. For example, high-frequency ripple at the output of a switching buck or boost regulator results in a common-mode voltage at the inputs of the MAX9938. Alternatively, fast load-current transients, when measuring at the input of a switching buck or boost regulator, can cause high-frequency differential sense voltages to occur at the inputs of the MAX9938, although the signal of interest is the average DC value. Such highfrequency differential sense voltages may result in a voltage offset at the MAX9938 output. _______________________________________________________________________________________ 7 MAX9938 Applications Information MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier The MAX9938 allows two methods of filtering to help improve performance in the presence of input commonmode voltage and input differential voltage transients. Figure 1 shows a differential input filter. The capacitor CIN between RS+ and RS- along with the resistor RIN between the sense resistor and RS- helps filter against input differential voltages and prevents them from reaching the MAX9938. The corner frequency of this filter is determined by the choice of RIN, CIN, and the value of the input resistance at RS- (R1). See Table 1 for R1 values at the different gain options. The value of RIN should be chosen to minimize its effect on the input offset voltage due to the bias current at RS-. RIN x IBIAS contributes to the input voltage offset. IBIAS is typically 0.2μA. Placing RIN at the RS- input does not affect the gain error of the device because the gain is given by the ratio between ROUT and R1 at RS+. Figure 2 shows the input common-mode filter. Again, the corner frequency of the filter is determined by the choice of RIN, CIN and is affected by R1. In this case RIN affects both gain error and input offset voltage. RIN should be smaller than R1 so that it has negligible effect on the device gain. If, for example, a filter with RIN = 10Ω and CIN = 1μF is built, then depending upon the gain selection, the gain error is affected by either 2.5% (G = 25V/V, R1 = 400Ω) or 5% (G = 50V/V, R1 = 200Ω) or 10% (G = 100V/V, R1 = 100Ω) or 10% (G = 200V/V, R1 = 100Ω). RSENSE RSENSE RIN RIN RIN LOAD LOAD CIN CIN RS+ RSMAX9938 8 RS+ RS- OUT MAX9938 GND Figure 1. Differential Input Filter OUT CIN GND Figure 2. Input Common-Mode Filter _______________________________________________________________________________________ 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ILOAD For the latest application details on UCSP construction, dimensions, tape carrier information, PCB techniques, bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability testing results, refer to the Application Note 1891: Wafer-Level Packaging (WLP) and Its Applications available on Maxim’s website at www.maximic.com/ucsp. RSENSE TO WALL-CUBE/ CHARGER VBATT = 1.6V TO 28V RS+ RS- RS+ RSLOAD R1 R1 R1 P P MAX9938 ROUT R1 10kΩ GND MAX9938 OUT ROUT OUT VDD = 3.3V 10kΩ μC GND ADC ADC Figure 3. Bidirectional Application Chip Information PROCESS: BiCMOS _______________________________________________________________________________________ 9 MAX9938 UCSP Applications Information Bidirectional Application Battery-powered systems may require a precise bidirectional current-sense amplifier to accurately monitor the battery’s charge and discharge currents. Measurements of the two separate outputs with respect to GND yields an accurate measure of the charge and discharge currents respectively (Figure 3). MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Package Information 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. 10 LAND PATTERN NO. PACKAGE TYPE PACKAGE CODE OUTLINE NO. 2 x 2 UCSP B4+1 21-0117 — 5 SOT23 U5-2 21-0057 90-0174 6 μDFN L622+1 21-0164 90-0004 ______________________________________________________________________________________ 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier SOT-23 5L .EPS ______________________________________________________________________________________ 11 MAX9938 Package Information (continued) 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. MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Package Information (continued) 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. 12 ______________________________________________________________________________________ 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier ______________________________________________________________________________________ 13 MAX9938 Package Information (continued) 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. MAX9938 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 4/08 Initial release 1 9/08 Added μDFN package information 2 2/09 Added G45 designation to part number 3 10/09 Added Input Filters section and MAX9938W to the data sheet 4 2/10 Updated EC table and Input Filters section 5 8/10 Removed Power-Up Time parameter 2 6 1/11 Corrected error on Figure 2 8 DESCRIPTION — 1, 2, 4, 5, 9 1 1, 2, 6–9 2, 8 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 © 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.