EVALUATION KIT AVAILABLE 1µA, 4-Bump UCSP/SOT23, Precision Current-Sense Amplifier

Transcription

1 19-521; Rev 2; 8/1 EVALUATION KIT AVAILABLE 1µA, 4-Bump UCSP/SOT23, General Description The high-side current-sense amplifier offers precision accuracy specifications of V OS less than 25µV (max) and gain error less than.5% (max). Quiescent supply current is an ultra-low 1µA. The 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 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 (T), 5V/V (F), 1V/V (H), and 2V/V (W). The four gain selections offer flexibility in the choice of the external current-sense resistor. The very low 25µV (max) input offset voltage allows small 25mV to 5mV full-scale voltage for very low voltage drop at full-current measurement. The is offered in tiny 4-bump UCSP (1mm x 1mm x.6mm footprint) and 5-pin SOT23 packages specified for operation over the -4 C to +85 C extended temperature range. Cell Phones PDAs Power-Management Systems Portable/Battery-Powered Systems Notebook Computers Applications Features Ultra-Low Supply Current of 1µA (max) Low 25µV (max) Input Offset Voltage Low <.5% (max) Gain Error Input Common Mode: +1.6V to +28V Voltage Output Four Gain Versions Available 25V/V (T) 5V/V (F) 1V/V (H) 2V/V (W) Tiny 1mm x 1mm x.6mm, 4-Bump UCSP or 5-Pin SOT23 Packages PART Ordering Information PIN- PACKAGE GAIN (V/V) TOP MARK TERS+ 4 UCSP 25 +ABX FERS+ 4 UCSP 5 +ABY HERS+ 4 UCSP 1 +ABZ WERS+ 4 UCSP 2 +ACA TEUK+ 5 SOT AFHG FEUK+ 5 SOT23 5 +AFHH HEUK+ 5 SOT23 1 +AFHI WEUK+ 5 SOT23 2 +AFHJ +Denotes a lead(pb)-free/rohs-compliant package. Note: All devices are specified over the -4 C to +85 C extended temperature range. TOP VIEW (BUMPS ON BOTTOM) UCSP is a trademark of Maxim Integrated Products, Inc. RS+ RS- 5 4 Pin Configurations RS+ A1 A2 RS- T/F/H/W T/F/H/W GND B1 B2 OUT DRAWINGS NOT TO SCALE UCSP GND GND OUT SOT23 Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS RS+, RS- to GND...-.3V to +3V OUT to GND...-.3V to +6V RS+ to RS-...±3V Short-Circuit Duration: OUT to GND...Continuous Continuous Input Current (any pin)...±2ma Continuous Power Dissipation (T A = +7 C) 4-Bump UCSP (derate 3.mW/ C above +7 C)...238mW 5-Pin SOT23 (derate 3.9mW/ C above +7 C)...312mW Operating Temperature Range...-4 C to +85 C Junction Temperature C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) 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 (V RS+ = V RS- = 3.6V, = (V RS+ - V RS- ) = V, T A = -4 C to +85 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Current (Note 2) I CC V RS+ = 5V, T A = +25 C.5.85 V RS+ = 5V, -4 C < T A < +85 C 1.1 V RS+ = 28V, T A = +25 C V RS+ = 28V, -4 C < T A < +85 C 2.5 Common-Mode Input Range V CM Guaranteed by CMRR, -4 C < T A < +85 C V Common-Mode Rejection Ratio CMR.6V < V RS+ < 28V, -4 C < T A < +85 C db Input Offset Voltage (Note 3) V OS W Gain Gain Error (Note 4) G GE T/F/ T A = +25 C 1 25 H -4 C < T A < +85 C 3 T A = +25 C C < T A < +85 C 425 T 25 F 5 H 1 W 2 T/F/ T A = +25 C ±.1 ±.5 H -4 C < T A < +85 C ±.6 W T A = +25 C ±.1 ±.7-4 C < T A < +85 C ±.8 T/F/H Output Resistance (Note 5) R OUT W µa µv V/V % kω Gain = OUT Low Voltage V OL Gain = Gain = Gain = mv 2

3 ELECTRICAL CHARACTERISTICS (continued) (V RS+ = V RS- = 3.6V, = (V RS+ - V RS- ) = V, T A = -4 C to +85 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS OUT High Voltage V OH V OH = V RS- - (Note 6).1.2 V Small-Signal Bandwidth (Note 5) BW = 5mV, gain = = 5mV, gain = 5 6 = 5mV, gain = 1 3 = 5mV, gain = 2 15 Output Settling Time t S 1% final value, = 5mV 1 µs Note 1: All devices are 1% production tested at T A = +25 C. All temperature limits are guaranteed by design. Note 2: =. I CC is the total current into RS+ plus RS- pins. Note 3: V OS is extrapolated from measurements for the gain-error test. Note 4: Gain error is calculated by applying two values of and calculating the error of the slope vs. the ideal: Gain = 25, is 2mV and 12mV. Gain = 5, is 1mV and 6mV. Gain = 1, is 5mV and 3mV. Gain = 2, is 2.5mV and 15mV. Note 5: The device is stable for any external capacitance value. Note 6: V OH is the voltage from V RS- to with = 3.6V/gain. khz (V RS+ = V RS- = 3.6V, T A = +25 C, unless otherwise noted.) Typical Operating Characteristics 3 25 INPUT OFFSET VOLTAGE HISTOGRAM toc GAIN ERROR HISTOGRAM toc SUPPLY CURRENT vs. TEMPERATURE 28V toc3 N (%) N (%) SUPPLY CURRENT (µa) V 1.8V INPUT OFFSET VOLTAGE (mv) GAIN ERROR (%) TEMPERATURE ( C) 3

4 Typical Operating Characteristics (continued) (V RS+ = V RS- = 3.6V, T A = +25 C, unless otherwise noted.) INPUT OFFSET (µv) INPUT OFFSET vs. COMMON-MODE VOLTAGE toc4 INPUT OFFSET (µv) INPUT OFFSET vs. TEMPERATURE toc5 SUPPLY CURRENT (µa) SUPPLY CURRENT vs. COMMON-MODE VOLTAGE toc COMMON-MODE VOLTAGE (V) TEMPERATURE ( C) COMMON-MODE VOLTAGE (V) GAIN ERROR (%) GAIN ERROR vs. COMMON-MODE VOLTAGE toc7 GAIN ERROR (%) GAIN ERROR vs. TEMPERATURE toc8 VOUT (V) vs. (SUPPLY = 3.6V) G = 1 G = 5 G = 25 toc VOLTAGE (V) TEMPERATURE ( C) (mv) VOUT (V) vs. (SUPPLY = 1.6V) G = 1 G = 5 G = 25 toc1 GAIN (db) SMALL-SIGNAL GAIN vs. FREQUENCY A V = 25V/V A V = 1V/V A V = 5V/V toc11 CMRR (db) CMRR vs. FREQUENCY G = 25 G = 5 G = 1 toc (mv) k 1k 1k 1M FREQUENCY (Hz) k 1k 1k 1M FREQUENCY (Hz) 4

5 Typical Operating Characteristics (continued) (V RS+ = V RS- = 3.6V, T A = +25 C, unless otherwise noted.) SMALL-SIGNAL PULSE RESPONSE (GAIN = 1) toc13a 15mV SMALL-SIGNAL PULSE RESPONSE (GAIN = 5) toc13b 3mV SMALL-SIGNAL PULSE RESPONSE (GAIN = 25) toc13c 6mV 1mV 2mV 4mV 1.5V 1.5V 1.5V 1V 1V 1V 2µs/div 25µs/div 25µs/div LARGE-SIGNAL PULSE RESPONSE (GAIN = 1) toc14a LARGE-SIGNAL PULSE RESPONSE (GAIN = 5) toc14b LARGE-SIGNAL PULSE RESPONSE (GAIN = 25) toc14c 3mV 6mV 12mV 1mV 1mV 2mV 3V 3V 3V 1V.5V.5V 2µs/div 25µs/div 25µs/div Pin Description PIN UCSP SOT23 NAME FUNCTION A1 5 RS+ External Sense Resistor Power-Side Connection A2 4 RS- External Sense Resistor Load-Side Connection B1 1, 2 GND Ground B2 3 OUT Output Voltage. is proportional to = V RS+ - V RS-. 5

6 V BATT = 1.6V TO 28V I LOAD RS+ R SENSE RS- Typical Operating Circuit V DD = 3.3V LOAD µc P OUT ADC R OUT 1kΩ GND Detailed Description The 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 monitors current through a current-sense resistor and amplifies the voltage across that resistor. The 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, such that its voltage drop equals the voltage drop across an external sense resistor, R SENSE. There is an internal resistor at RS- with the Table 1. Internal Gain-Setting Resistors (Typical Values) GAIN (V/V) (Ω) R OUT (kω) same value as to minimize offset voltage. The current through 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, R OUT. This produces an output voltage,, whose magnitude is I LOAD x R SENSE x R OUT /. The gain accuracy is based on the matching of the two gain resistors and R OUT (see Table 1). Total gain = 25V/V for the T, 5V/V for the F, 1V/V for the H, and 2V/V for the W. The output is protected from input overdrive by use of an output current-limiting circuit of 7mA (typical) and a 6V clamp protection circuit. Applications Information 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 drop due to IR loss. For minimal voltage loss, use the lowest R SENSE value. 6

7 OUT Swing vs. V RS+ and The is unique because the supply voltage is the input common-mode voltage (the average voltage at RS+ and RS-). There is no separate V CC supply voltage pin. Therefore, the OUT voltage swing is limited by the minimum voltage at RS+. (max) = V RS+ (min) - (max) - V OH and: VOUT (max) RSENSE = G ILOAD (max) full scale should be less than /GAIN at the minimum RS+ voltage. For best performance with a 3.6V supply voltage, select R SENSE to provide approximately 12mV (gain of 25V/V), 6mV (gain of 5V/V), 3mV (gain of 1V/V), or 15mV (gain of 2V/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 (max)), there are two components to accuracy: input offset voltage (V OS ) and gain error (GE). For the, V OS = 25µV (max) and gain error is.5% (max). Use the linear equation: = (gain ± GE) x ± (gain x V OS ) to calculate total error. A high R SENSE 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 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. The precision V OS of the 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 R SENSE, 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 constant during sampling. This also decreases the small-signal bandwidth of the currentsense amplifier and reduces noise at OUT. 7

8 V BATT = 1.6V TO 28V I LOAD RS+ R SENSE RS- RS+ RS- LOAD TO WALL-CUBE/ CHARGER P P OUT OUT V DD = 3.3V R OUT 1kΩ R OUT 1kΩ µc GND GND ADC ADC Figure 1. Bidirectional Application 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 1). UCSP Applications Information 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 Application Note 1891: Wafer- Level Packaging (WLP) and Its Applications.. PROCESS: BiCMOS Chip Information 8

9 Package Information For the latest package outline information and land patterns, go to 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 R41A SOT23 U x2 UCSP.EPS 9

10 Package Information (continued) For the latest package outline information and land patterns, go to 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. SOT-23 5L.EPS 1

11 REVISION NUMBER REVISION DATE DESCRIPTION Revision History PAGES CHANGED 1/9 Initial release 1 2/1 Corrected gain error limits in Electrical Characteristics table 2 2 8/1 Removed Power-Up Time parameter 3 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, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.