EVALUATION KIT AVAILABLE MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier General Description The MAX9938 high-side current-sense amplifier offers precision accuracy specifications of VOS less than 500V (max) and gain error less than 0.5% (max). Quiescent supply current is an ultra-low 1A. The MAX9938 fits in a tiny, 1mm x 1mm UCSPTM package size or a 5-pin SOT23 package, making the part ideal for applications in notebook computers, cell phones, PDAs, and all batteryoperated 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). The four gain selections offer flexibility in the choice of the external current-sense resistor. The very low 500V (max) input offset voltage allows small 25mV to 50mV full-scale VSENSE voltage for very low voltage drop at full-current measurement. Features Ultra-Low Supply Current of 1A (max) Low 500V (max) Input Offset Voltage Low < 0.5% (max) Gain Error Input Common Mode: +1.6V to +28V Voltage Output Four Gain Versions Available * +25V/V (MAX9938T) * 50V/V (MAX9938F) * 100V/V (MAX9938H) * 200V/V (MAX9938W) Tiny 1mm x 1mm x 0.6mm, 4-Bump UCSP, 5-Pin SOT23, or 2mm x 2mm x 0.8mm, 6-Pin DFN Packages Ordering Information The MAX9938 is offered in tiny 4-bump, UCSP (1mm x 1mm x 0.6mm footprint), 5-pin SOT23, and 6-pin DFN (2mm x 2mm x 0.8mm) packages specified for operation over the -40C to +85C extended temperature range. Applications Cell Phones PDAs Power Management Systems Portable/Battery-Powered Systems Notebook Computers PINPACKAGE PART GAIN (V/V) TOP MARK 25 +AGD MAX9938TEBS+G45 4 UCSP MAX9938FEBS+G45 4 UCSP 50 +AGE MAX9938HEBS+G45 4 UCSP 100 +AGF MAX9938WEBS+G45 4 UCSP 200 +AGI MAX9938TEUK+ 5 SOT23 25 +AFFB MAX9938FEUK+ 5 SOT23 50 +AFFC MAX9938HEUK+ 5 SOT23 100 +AFFD MAX9938WEUK+ 5 SOT23 200 +AFGZ MAX9938FELT+ 6 DFN 50 +ACM +Denotes a lead(Pb)-free/RoHS-compliant package. G45 indicates protective die coating. Note: All devices are specified over the -40C to +85C extended temperature range. UCSP is a trademark of Maxim Integrated Products, Inc. Pin Configurations TOP VIEW (BUMPS ON BOTTOM) RS+ RS+ 5 A1 A2 RS- B2 OUT MAX9938T MAX9938F MAX9938H MAX9938W MAX9938T MAX9938F MAX9938H MAX9938W GND B1 UCSP DRAWINGS NOT TO SCALE 19-4110; Rev 7; 4/17 1 GND TOP VIEW (PADS ON BOTTOM) RS4 2 GND SOT23 3 OUT OUT 1 6 RS- N.C. 2 MAX9938FELT 5 N.C. GND 3 4 RS+ DFN MAX9938 nanoPower, 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 = +70C) 4-Bump UCSP (derate 3.0mW/C above +70C).........238mW 5-Pin SOT23 (derate 3.9mW/C above +70C)...........312mW 6-Pin DFN (derate 4.5mW/C above +70C).............358mW Operating Temperature Range............................ -40C to +85C Junction Temperature.......................................................+150C Storage Temperature Range............................. -65C to +150C Lead Temperature (excluding UCSP, soldering, 10s)...... +300C Soldering Temperature (reflow)........................................+260C 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 = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN VRS+ = 5V, TA = +25C Supply Current (Note 2) ICC TYP MAX 0.5 0.85 VRS+ = 5V, -40C < TA < +85C 1.1 VRS+ = 28V, TA = +25C 1.1 1.8 VRS+ = 28V, -40C < TA < +85C Common-Mode Input Range Common-Mode Rejection Ratio Input Offset Voltage (Note 3) VCM CMRR VOS Gain Error (Note 4) G Guaranteed by CMRR , -40C < TA < +85C 1.6 1.6V < VRS+ < 28V, -40C < TA < +85C 94 TA = +25C GE OUT Low Voltage OUT High Voltage Small-Signal Bandwidth (Note 5) Output Settling Time www.maximintegrated.com ROUT VOL VOH BW tS 500 600 V 25 50 MAX9938H 100 MAX9938W 200 V/V TA = +25C -40C < TA < +85C 0.1 TA = +25C 0.1 0.5 0.6 -40C < TA < +85C 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 VSENSE = 50mV, gain = 200 15 1% final value, VSENSE = 50mV 100 (Note 5) V dB 100 MAX9938F MAX9938W Output Resistance 28 130 -40C < TA < +85C MAX9938T/MAX9938F/ MAX9938H A 2.5 MAX9938T Gain UNITS k mV V V kHz s Maxim Integrated 2 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Electrical Characteristics (continued) (VRS+ = VRS- = 3.6V, VSENSE = (VRS+ - VRS-) = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) Note Note Note Note 1: 2: 3: 4: All devices are 100% production tested at TA = +25C. 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. Typical Operating Characteristics (VRS+ = VRS- = 3.6V, TA = +25C, unless otherwise noted.) 25 20 N (%) 15 10 10 5 5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.4 1.8V -0.4 -0.3 -0.2 -0.1 0 0 0.1 0.2 0.3 0.4 -40 -15 10 35 60 TEMPERATURE (C) INPUT OFFSET vs. COMMON-MODE VOLTAGE INPUT OFFSET vs. TEMPERATURE SUPPLY CURRENT vs. COMMON-MODE VOLTAGE -45 -50 50 40 30 20 10 5 10 15 20 SUPPLY VOLTAGE (V) www.maximintegrated.com 25 30 0 1.4 85 MAX9938 toc06 60 INPUT OFFSET (V) -40 0 3.6V 0.6 GAIN ERROR (%) -35 -55 0.8 INPUT OFFSET VOLTAGE (mV) MAX9938 toc04 -30 0 28V 1.0 0.2 1.2 SUPPLY CURRENT (A) 0 INPUT OFFSET (V) 15 MAX9938 toc05 N (%) 20 1.2 SUPPLY CURRENT (A) 25 1.4 MAX9938 toc02 30 MAX9938 toc01 30 SUPPLY CURRENT vs. TEMPERATURE MAX9938 toc03 GAIN ERROR HISTOGRAM INPUT OFFSET VOLTAGE HISTOGRAM 1.0 0.8 0.6 0.4 0.2 -40 -15 10 35 TEMPERATURE (C) 60 85 0 0 5 10 15 20 25 30 SUPPLY VOLTAGE (V) Maxim Integrated 3 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Typical Operating Characteristics (continued) (VRS+ = VRS- = 3.6V, TA = +25C, unless otherwise noted.) 0.06 -0.2 -0.3 -0.4 5 10 15 20 25 0.04 0.02 1.0 0.01 0.5 0 -40 VOUT vs. VSENSE (SUPPLY = 1.6V) 1.4 0 G = 100 GAIN (dB) VOUT (V) 1.2 G = 50 G = 25 0.6 0.2 20 40 60 MAX9938 toc09 50 0 80 100 AV = 50V/V -15 -30 150 CMRR vs. FREQUENCY 0 -20 G = 25 -40 AV = 100V/V -10 100 VSENSE (mV) G = 50 -60 -80 G = 100 -100 -120 -25 0 0 85 -20 0.4 0 60 AV = 25V/V -5 0.8 35 SMALL SIGNAL GAIN vs. FREQUENCY 5 MAX9938 toc10 1.6 1.0 10 G = 25 TEMPERATURE (C) VOLTAGE (V) 1.8 -15 G = 50 2.0 1.5 30 G = 100 2.5 0.03 CMRR (dB) 0 3.0 MAX9938 toc11 -0.5 0.05 3.5 VOUT (V) GAIN ERROR (%) -0.1 0.07 VOUT vs. VSENSE (SUPPLY = 3.6V) 4.0 MAX9938 toc08 0 GAIN ERROR (%) 0.08 MAX9938 toc07 0.1 GAIN ERROR vs. TEMPERATURE MAX9938 toc12 GAIN ERROR vs. COMMON-MODE VOLTAGE -140 1Hz VSENSE (mV) 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz -160 1Hz 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz FREQUENCY (kHz) FREQUENCY (kHz) SMALL-SIGNAL PULSE RESPONSE (GAIN = 100) SMALL-SIGNAL PULSE RESPONSE (GAIN = 50) MAX9938 toc13a MAX9938 toc13b 30mV 15mV VSENSE 10mV VSENSE 20mV 1.5V 1.5V VOUT 1V 20s/div www.maximintegrated.com VOUT 1V 25s/div Maxim Integrated 4 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Typical Operating Characteristics (continued) (VRS+ = VRS- = 3.6V, TA = +25C, unless otherwise noted.) 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 25s/div 20s/div LARGE-SIGNAL PULSE RESPONSE (GAIN = 50) LARGE-SIGNAL PULSE RESPONSE (GAIN = 25) MAX9938 toc14b MAX9938 toc14c 120mV 60mV VSENSE VSENSE 10mV 20mV 3V 3V VOUT VOUT 0.5V 0.5V 25s/div 25s/div Pin Description PIN NAME FUNCTION UCSP SOT23 DFN 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. www.maximintegrated.com Maxim Integrated 5 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Typical Operating Circuit ILOAD RSENSE VBATT = 1.6V TO 28V RS+ R1 RSR1 VDD = 3.3V LOAD C P MAX9938 ROUT OUT ADC 10k 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 ILOAD x RSENSE x ROUT/R1. The gain accuracy is based on the matching of the two gain resistors R1 and ROUT (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) GAIN (V/V) R1 () ROUT (k) 200 100 20 100 100 10 50 200 10 25 400 10 www.maximintegrated.com Maxim Integrated 6 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Applications Information 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 R SENSE = VOUT (max) G x 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 = 500V (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. www.maximintegrated.com 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, highfrequency 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 high-frequency differential sense voltages may result in a voltage offset at the MAX9938 output. Maxim Integrated 7 MAX9938 nanoPower, 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. 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+. 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. 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 = 10 and CIN = 1F is built, then depending upon the gain selection, the gain error is affected by either 2.5% (G = 25V/V, R1 = 400) or 5% (G = 50V/V, R1 = 200) or 10% (G = 100V/V, R1 = 100) or 10% (G = 200V/V, R1 = 100). 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 0.2A. Figure 2 shows the input common-mode filter. RSENSE RSENSE RIN RIN RIN LOAD LOAD CIN CIN RS+ RS- MAX9938 GND Figure 1. Differential Input Filter www.maximintegrated.com OUT CIN RS+ RS- MAX9938 OUT GND Figure 2. Input Common-Mode Filter Maxim Integrated 8 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier 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). 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.maximintegrated. com/ucsp. RSENSE TO WALL-CUBE/ CHARGER VBATT = 1.6V TO 28V RS+ RS- RS+ RSLOAD R1 R1 R1 P P MAX9938 ROUT R1 10k GND MAX9938 OUT ROUT 10k OUT VDD = 3.3V C GND ADC ADC Figure 3. Bidirectional Application Chip Information PROCESS: BiCMOS www.maximintegrated.com Maxim Integrated 9 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier 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 OUTLINE NO. LAND PATTERN NO. 2 x 2 UCSP B4+1 21-0117 -- 5 SOT23 U5-2 21-0057 90-0174 6 DFN L622+1 21-0164 90-0004 www.maximintegrated.com Maxim Integrated 10 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Package Information (continued) SOT-23 5L .EPS 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. www.maximintegrated.com Maxim Integrated 11 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Package Information (continued) 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. www.maximintegrated.com Maxim Integrated 12 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Package Information (continued) 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. www.maximintegrated.com Maxim Integrated 13 MAX9938 nanoPower, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 4/08 Initial release 1 9/08 Added DFN 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 7 4/17 Updated title of data sheet to include "nanoPower" DESCRIPTION -- 1, 2, 4, 5, 9 1 1, 2, 6-9 2, 8 1-14 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. (c) 2017 Maxim Integrated Products, Inc. 14 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX9938FELT+T MAX9938FEUK+T MAX9938HEBS+T MAX9938HEUK+T MAX9938TEBS+T MAX9938TEUK+T MAX9938FEBS+TG45 MAX9938HEBS+TG45 MAX9938TEBS+TG45 MAX9938WEUK+T MAX9938WEBS+TG45