MAX9918/MAX9919/MAX9920

Transcription

1 19-515; Rev 4; 7/11 EVALUATION KIT AVAILABLE -2V to +75V Input Range, Precision General Description The /MAX9919/MAX992 are single-supply, high-accuracy current-sense amplifiers with a high input common-mode range that extends from -2V to +75V. These amplifiers are well suited for current monitoring of inductive loads such as motors and solenoids, where common-mode voltages can become negative due to inductive kickback, reverse-battery conditions, or transient events. The /MAX992 feature adjustable gain set by an external resistive-divider network. The MAX9919 features fixed gains of 45V/V (MAX9919F) and 9V/V (MAX9919N). The /MAX9919/MAX992 operate as unidirectional amplifiers when V REFIN = GND and as bidirectional amplifiers when V REFIN = V CC /2. The MAX992 attenuates the input signal by a factor of 4 at the input level-shifting stage allowing the device to sense voltages up to 2mV (unidirectional operation) or ±1mV (bidirectional operation). The /MAX9919/MAX992 operate with a single 5V supply voltage, are fully specified over the -4 C to +125 C automotive temperature range, and are available in an 8-pin SOIC package. Applications H-Bridge Motor Current Sensing Solenoid Current Sensing Current Monitoring of Inductive Loads High- and Low-Side Precision Current Sensing 4x4 Transmission Control Electronic Throttle Control Super-Capacitor Charge/Discharge Monitoring in Hybrid Cars Precision High-Voltage Current Monitoring Features -2V to +75V Input Common-Mode Voltage Range 4µV (max) Input Offset Voltage.6% (max) Gain Accuracy Error Uni- or Bidirectional Current Sensing Reference Input for Bidirectional OUT 12kHz, -3dB Bandwidth (MAX9919N) Single-Supply Operation (4.5V to 5.5V) 1mA Supply Current.5µA (typ) Shutdown Current Rail-to-Rail Output -4 C to +125 C Automotive Temperature Range PART Ordering Information/ Selector Guide V SENSE (mv) GAIN (V/V) PIN- PACKAGE ASA+ ±5 Adjustable 8 SOIC-EP* ASA/V+ ±5 Adjustable 8 SOIC-EP* MAX9919FASA+ ± SOIC-EP* MAX9919NASA+ ±5 9 8 SOIC-EP* MAX9919NASA/V+ ±5 9 8 SOIC-EP* MAX992ASA+ ±2 Adjustable 8 SOIC-EP* MAX992ASA/V+ ±2 Adjustable 8 SOIC-EP* Note: All devices operate over the -4 C to +125 C temperature range. +Denotes a lead(pb)-free/rohs-compliant package. /V denotes an automotive qualified part. *EP = Exposed pad. Typical Operating Circuit /MAX9919/MAX992 V BATT V CC V CC φ1a R SENSE M φ2b RS+ MAX992 A OUT FB R2 ADC φ2b φ1b RS- SHDN INPUT STAGE LEVEL SHIFTER GND ADJUSTABLE GAIN REFIN R1 REF GND μc Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 -2V to +75V Input Range, Precision /MAX9919/MAX992 ABSOLUTE MAXIMUM RATINGS V CC to GND...-.3V to +6V RS+, RS- to GND (V CC = 5V)...-3V to +8V RS+, RS- to GND (V CC = V)...-15V to +8V (15 minutes) Differential Input Voltage (V RS+ - V RS- ) (/MAX9919)...±15V (Continuous) Differential Input Voltage (V RS+ - V RS- ) (MAX992)...±5V (Continuous) REFIN, FB, OUT to GND...-.3V to (V CC +.3V) SHDN to GND...-.3V to +2V **As per JEDEC51 Standard (multilayer board). PACKAGE THERMAL CHARACTERISTICS (Note 1) SOIC-EP Junction-to-Ambient Thermal Resistance (θ JA )...41 C/W 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 Output Short Circuit to V CC or GND...Continuous Continuous Current into Any Pin (Not to exceed package power dissipation)...±2ma Continuous Power Dissipation (T A = +7 C) 8-Pin SOIC-EP (derate 24.4mW/ C above +7 C) mW** Junction Temperature C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s)...+3 C Soldering Temperature (reflow) C Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to (V CC = 5V, +14V, V SENSE = (V RS+ - V RS- ) = V, V SHDN = V GND = V, V REFIN = V CC /2, R L = 1kΩ; for, A V = 9V/V, R2/R1 = 89kΩ/1kΩ; for MAX992, A V = 2V/V, R2/R1 = 79kΩ/1kΩ; T A = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Offset Voltage (Note 2) V OS MAX9919_ MAX V, V REFIN = V -2V, V REFIN = V +14V, V REFIN = V -2V, V REFIN = V +14V, V REFIN = V -2V, V REFIN = V T A = +25 C ±.14 ±.4 T A = -4 C to +125 C ±.7 T A = +25 C ±.8 ±.4 T A = -4 C to +125 C ±1.3 T A = +25 C ±.18 ±.4 T A = -4 C to +125 C ±.9 T A = +25 C ±.11 ±.4 T A = -4 C to +125 C ±1. T A = +25 C ±.48 ±1.2 T A = -4 C to +125 C ±3. T A = +25 C ±.1 ±.9 T A = -4 C to +125 C ±3.5 mv 2

3 -2V to +75V Input Range, Precision ELECTRICAL CHARACTERISTICS (continued) (V CC = 5V, +14V, V SENSE = (V RS+ - V RS- ) = V, V SHDN = V GND = V, V REFIN = V CC /2, R L = 1kΩ; for, A V = 9V/V, R2/R1 = 89kΩ/1kΩ; for MAX992, A V = 2V/V, R2/R1 = 79kΩ/1kΩ; T A = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETERS SYMBOL CONDITIONS MIN TYP MAX UNITS Input Offset Voltage Drift (Note 3) V OSD MAX9919_ MAX V ±1.2-2V ± V ±1.8-2V ± V ±2.4-2V ±8.8 Common-Mode Range V CM Inferred from CMRR tests V Common-Mode Rejection Ratio (Note 3) CMRR -2V V CM +14V 8 M AX 9918, M AX V VCM +75V 96 MAX992-2V V CM +14V 72-2V V CM +75V 86 T A = +25 C ±175 Input Bias Current I RS+, I RS- -2V V CM +75V TA = -4 C to +125 C ±25 Input Offset Current ( I RS + - I RS - ) ±8 μa Input Leakage Current in Shutdown μv/ C -2V V CM +75V, V SHDN = V CC = 5V ±3 μa Input Leakage Current +14V, +75V, V CC = V ±3 μa Input Resistance, Common mode 3 kω MAX9919_ Differential 715 Ω MAX992 Common mode 33 kω Differential 224 Ω Inferred from gain, MAX9919_ 5 Full-Scale Sense Voltage (Note 4) V SENSE error test MAX992 2 Gain (Notes 2, 4) G, MAX992 Adj MAX9919F 45 MAX9919N 9 3 Minimum Adjustable Gain G ADJ MAX db μa mv V/V V/V /MAX9919/MAX992 3

4 -2V to +75V Input Range, Precision /MAX9919/MAX992 ELECTRICAL CHARACTERISTICS (continued) (V CC = 5V, +14V, V SENSE = (V RS+ - V RS- ) = V, V SHDN = V GND = V, V REFIN = V CC /2, R L = 1kΩ; for, A V = 9V/V, R2/R1 = 89kΩ/1kΩ; for MAX992, A V = 2V/V, R2/R1 = 79kΩ/1kΩ; T A = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) Gain Error (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GE MAX9919F +14V -2V, V REFIN = V +14V, V REFIN = V -2V, V REFIN = V +14V, V REFIN = V MAX9919N VRS+ = V RS- = -2V, V REFIN = V MAX V, V REFIN = V -2V, V REFIN = V T A = +25 C, V REFIN = V T A = -4 C to +125 C, V REFIN = V ±.8 ±.6 ±1.2 T A = +25 C ±.2 ±.6 T A = -4 C to +125 C ±1. T A = +25 C ±.13 ±.45 T A = -4 C to +125 C ±1.2 T A = +25 C ±.1 ±.45 T A = -4 C to +125 C ±.9 T A = +25 C ±.16 ±.6 T A = -4 C to +125 C ±1.2 T A = +25 C ±.11 ±.6 T A = -4 C to +125 C ±1. T A = +25 C ±.29 ±1. T A = -4 C to +125 C ±1.7 T A = +25 C ±.24 ±1. T A = -4 C to +125 C FB Input Bias Current I FB, MAX na V SENSE = 2mV for R L = 1kΩ to GND 3 1, MAX9919_, Output-Voltage High (Note 4) V CC - V OH V SENSE = 4mV for R L = 1kΩ to GND 12 4 MAX992 V SENSE = -2mV for R L = 1kΩ to V CC 3 1, MAX9919_, Output-Voltage Low (Note 4) V OL V SENSE = -4mV for R L = 1kΩ to V CC 1 4 MAX992 OUT shorted to V CC 44 Short-Circuit Current I SC OUT shorted to GND 41 ±1.7 % mv mv ma Output Resistance R OUT.1 Ω REFIN Voltage Range Inferred from REFIN CMRR test M AX 9918, M AX9919_ MAX992 4 V CC /2 V CC /2 V CC V CC V

5 -2V to +75V Input Range, Precision ELECTRICAL CHARACTERISTICS (continued) (V CC = 5V, +14V, V SENSE = (V RS+ - V RS- ) = V, V SHDN = V GND = V, V REFIN = V CC /2, R L = 1kΩ; for, A V = 9V/V, R2/R1 = 89kΩ/1kΩ; for MAX992, A V = 2V/V, R2/R1 = 79kΩ/1kΩ; T A = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETERS SYMBOL CONDITIONS MIN TYP MAX UNITS REFIN Common-Mode Rejection Ratio RE FIN C M R R, MAX9919_ MAX992 V V REFIN (V CC - 1.9V) V V REFIN (V CC - 2.4V) M AX 9918, M AX 9919_, V RS + = V RS - = ± 5m V ±1 REFIN Current I REFIN MAX992, ±2mV ±1 SHDN Logic-High V IH 2. V SHDN Logic-Low V IL.8 V SHDN Logic Input Current V SHDN V CC 5 μa Supply Voltage Range V CC Inferred from PSRR test V Power-Supply Rejection Ratio (Note 3) PSRR, MAX9919_ 4.5V V CC 5.5V MAX V V CC 5.5V V Supply Current I CC -2V T A = +25 C T A = - 4 C to C 1.5 T A = +25 C T A = - 4 C to C 2.2 Shutdown Supply Current I CC_SHDN V SHDN = V CC = 5V.5 1 μa Small Signal -3dB Bandwidth Slew Rate 1% Settling Time from V SENSE Step BW SR, V SENSE = 5mV 75 MAX9919F, V SENSE = 5mV 25 MAX9919N, V SENSE = 5mV 12 MAX992, V SENSE = 2mV 23.6 MAX9919F.9 MAX9919N 3. MAX MAX9919F V SENSE = 5mV to 5mV step 12 V SENSE = 5mV to 5mV step 7 V SENSE = 5mV to 5mV step 3.5 V SENSE = 5mV to 5mV step 2.5 V SENSE = 5mV to 5mV step 3.5 MAX9919N VSENSE = 5mV to 5mV step 3 db μa db ma khz V/μs μs /MAX9919/MAX992 MAX992 V S E N S E = 2m V to 2m V step 5 V S E N S E = 2m V to 2m V step 3 5

6 -2V to +75V Input Range, Precision /MAX9919/MAX992 ELECTRICAL CHARACTERISTICS (continued) (V CC = 5V, +14V, V SENSE = (V RS+ - V RS- ) = V, V SHDN = V GND = V, V REFIN = V CC /2, R L = 1kΩ; for, A V = 9V/V, R2/R1 = 89kΩ/1kΩ; for MAX992, A V = 2V/V, R2/R1 = 79kΩ/1kΩ; T A = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETERS SYMBOL CONDITIONS MIN TYP MAX UNITS 1% Settling Time from V CM Step Power-Up Time, V CM = -2V to +14V step 2.5 V SENSE = 5mV V CM = +14V to -2V step.5 MAX9919F, V CM = -2V to +14V step 2.5 V SENSE = 5mV V CM = +14V to -2V step.5 MAX9919N, V CM = -2V to +14V step 3.5 V SENSE = 5mV V CM = +14V to -2V step 3.5 MAX992, V CM = -2V to +14V step.25 V SENSE = 2mV V CM = +14V to -2V step 2.5, V SENSE = 5mV, 1% settling 4.5 MAX9919F, V SENSE = 5mV, 1% settling 5 MAX9919N, V SENSE = 5mV, 1% settling 6 MAX992, V SENSE = 2mV, 1% settling 5 Max Capacitive Load Stability No sustained oscillations (Note 5) 5 pf Input Referred Noise Voltage Density e n 1kHz, MAX9919_ 6 MAX Note 1: All devices are 1% production tested at T A = +25 C. All temperature limits are guaranteed by design. Note 2: V OS is extrapolated from two point gain error tests. Measurements are made at V SENSE = 5mV and 5mV for /MAX9919N/MAX9919F, and V SENSE = 2mV and 2mV for MAX992. Note 3: Extrapolated V OS as described above in Note 2 is used to calculate V OS drift, CMRR, and PSRR. Note 4: OUT should be 1mV away from either rail to achieve rated accuracy, or limited by a V SENSE of 5mV for the /MAX9919N/MAX9919F and 2mV for the MAX992. Note 5: Not production tested. Guaranteed by design. μs μs nv/ Hz 6

7 -2V to +75V Input Range, Precision (V CC = 5V, T A = +25 C, unless otherwise noted.) N (%) N (%) V OS (V RS+ = +14V) OFFSET VOLTAGE (FV) V OS DRIFT (V RS+ = -2V) OFFSET VOLTAGE (FV/ C) toc1 toc4 N (%) VOS (uv) V OS DRIFT (V RS+ = +14V) OFFSET VOLTAGE (FV/ C) ASA V CC = 5V V REF = V GND V OS vs. V CM T A = -4 C V CM (V) Typical Operating Characteristics T A = +25 C T A = +125 C toc2 toc5 N (%) VOS (FV) V OS (V RS+ = -2V) OFFSET VOLTAGE (FV) V OS vs. V CC V CM = 14V -5 ASA V CM = -2V -75 V CC = 5V V REF = V GND V CC (V) toc3 toc6 /MAX9919/MAX GAIN ERROR (V RS+ = +14V, MAX9919F, A V = +45V/V) toc7.8.7 GAIN ERROR (V RS+ = +14V, MAX9919N, A V = +9V/V) toc8.6.5 GAIN ERROR (V RS+ = -2V, MAX9919F, A V = +45V/V) toc N (%).3 N (%).4 N (%) GAIN ERROR (%) GAIN ERROR (%) GAIN ERROR (%) 7

8 -2V to +75V Input Range, Precision /MAX9919/MAX992 Typical Operating Characteristics (continued) (V CC = 5V, T A = +25 C, unless otherwise noted.) N (%) GAIN ERROR (%) GAIN ERROR (V RS+ = -2V, MAX9919N, A V = +9V/V) GAIN ERROR (%) V CM = -2V GAIN ERROR vs. V CC V CM = 14V V CC (V) toc1 toc12 GE (%) LINEARITY (%) T A = +125NC GAIN ERROR vs. V CM T A = +25NC ASA T A = -4NC -1.6 V CC = 5V V REF = V GND V CM (V) LINEARITY vs. V SENSE.25 V CM = -2V.2 V CC = 5V.15 V REFIN = V CC /2.1 T A = -4 C A V = 9V/V BIDIRECTIONAL T A = +125 C -.1 T A = +25 C V SENSE (mv) toc13 toc11 LINEARITY (%) LINEARITY vs. V SENSE T A = +25 C T A = -4 C T A = +125 C V CM = +14V V CC = 5V V REFIN = V CC /2 A V = 9V/V BIDIRECTIONAL V SENSE (mv) toc14 LINEARITY (%) T A = +25 C LINEARITY vs. V SENSE T A = +125 C T A = -4 C V CM = -2V V CC = 5V V REFIN = V GND A V = 9V/V UNIDIRECTIONAL V SENSE (mv) toc15 8

9 -2V to +75V Input Range, Precision Typical Operating Characteristics (continued) (V CC = 5V, T A = +25 C, unless otherwise noted.) LINEARITY (%) LINEARITY (%) LINEARITY vs. V SENSE V CM = +14V V CC = 5V V REFIN = V GND A V = 9V/V UNIDIRECTIONAL T A = +25 C T A = +125 C T A = -4 C V SENSE (mv) LINEARITY vs. V SENSE T A = -4 C T A = +125 C T A = +25 C V CM = +14V V CC = 5V V REFIN = V CC /2 A V = 3V/V BIDIRECTIONAL V SENSE (mv) toc16 toc18 LINEARITY (%) VOUT - VREFIN (V) LINEARITY vs. V SENSE T A = +25 C T A = +125 C V SENSE (mv) V OUT - V REFIN vs. V SENSE -2V V CM : SOLID LINE 14V V CM : DASHED LINE V CM = -2V V CC = 5V V REFIN = V CC /2 A V = 3V/V BIDIRECTIONAL T A = -4 C, V REFIN = V UNIDIRECTIONAL, GAIN = 9V/V V SENSE (mv) toc17 toc19 /MAX9919/MAX992 VOUT - VREFIN (V) V OUT - V REFIN vs. V SENSE 3. -2V V 2.5 CM : SOLID LINE 14V V CM : DASHED LINE , V REFIN = V CC /2-2. BIDIRECTIONAL, -2.5 GAIN = 9V/V V SENSE (mv) toc2 VOH AND VOL (mv) V OH /V OL vs. I OH V CM = +14V V CC - V OH V OL I OH (ma) toc21 9

10 -2V to +75V Input Range, Precision /MAX9919/MAX992 Typical Operating Characteristics (continued) (V CC = 5V, T A = +25 C, unless otherwise noted.) ICC (ma) INPUT LEAKAGE CURRENT (FA) I CC vs. V CC.1 V SENSE = V V CC (V) V CM = -2V V CM = 14V INPUT LEAKAGE CURRENT vs. V CM T A = +25NC T A = +125NC IN+ - IN- = 5mV V CC = V SHDN = V V REFIN = V T A = -4NC V CM (V) toc22 toc25 ICC (ma) DIFFERENTIAL RIN (I) I CC vs.v CM T A = +125NC V SENSE = V (DASH) V SENSE + 5mV (SOLID) T A = +25NC T A = -4NC V CM (V) DIFFERENTIAL R IN vs. V CM V CM (V) toc23 toc26 IBAIS (FA) GAIN (db) I BIAS vs. V CM V CC = 5V V CM (V) GAIN vs. FREQUENCY -2-3 V CM = 14V GAIN = 9V/V FREQUENCY (MHz) toc24 toc27 GAIN (db) GAIN vs. FREQUENCY -4 MAX992-5 V CM = 14V GAIN = 2V/V FREQUENCY (MHz) toc28 GAIN (db) GAIN vs. FREQUENCY 1 V CM = 14V -1 GAIN = 9V/V V CM = -2V V CM = 14V FREQUENCY (MHz) toc29 PSRR (db) V CM = 14V V SENSE = 5mV PSRR vs. FREQUENCY k 1k FREQUENCY (khz) toc3 1

11 -2V to +75V Input Range, Precision Typical Operating Characteristics (continued) (V CC = 5V, T A = +25 C, unless otherwise noted.) 5mV/div 5mV/div 5mV/div SMALL-SIGNAL TRANSIENT (GAIN = 45V/V) toc31, V CM = 14V V SENSE = 1mV TO 15mV 1Fs/div LARGE-SIGNAL TRANSIENT (GAIN = 45V/V) toc33 5mV/div 1mV/div 5mV/div SMALL-SIGNAL TRANSIENT (GAIN = 9V/V) toc32, V CM = 14V V SENSE = 1mV TO 15mV 1Fs/div LARGE-SIGNAL TRANSIENT (GAIN = 9V/V) toc34 /MAX9919/MAX992 5mV/div, V CM = 14V V SENSE = V TO 5mV 1V/div, V CM = 14V V SENSE = TO 5mV 1Fs/div 1Fs/div COMMON-MODE STEP RESPONSE toc35, V CM = 14V S SENSE = PS (5mV) OUTPUT RESPONSE TO COMMON-MODE TRANSIENT toc36 V CM 5V/div 1V/div 1V/div OUTPUT AC-COUPLED FULL SCALE AT THE INPUT V OUT 1mV/div 1Fs/div 4µs/div 11

12 -2V to +75V Input Range, Precision /MAX9919/MAX992 Typical Operating Characteristics (continued) (V CC = 5V, T A = +25 C, unless otherwise noted.) 5V/div 1V/div 2mV/div SHUTDOWN ON/OFF DELAY toc37 4Fs/div, V CM = 14V V SENSE = PS (5mV) OUTPUT OVERDRIVE RECOVERY (3V/V) toc39, V CM = 14V V SENSE = 2 x PS 5V/div 2V/div 5mV/div POWER-UP TIME 4Fs/div toc38, V CM = 14V V SENSE = PS (5mV) OUTPUT OVERDRIVE RECOVERY (9V/V) toc4 2V/div 2V/div, V CM = 14V V SENSE = 2 x PS 4Fs/div 4Fs/div 12

13 -2V to +75V Input Range, Precision PIN NAME FUNCTION 1 RS+ Positive Current-Sensing Input. Power side connects to external sense resistor. 2 RS- Negative Current-Sensing Input. Load side connects to external sense resistor. 3 SHDN Active-High Shutdown Input. Connect to GND for normal operation. 4 GND Ground 5 OUT Current-Sense Output. V OUT is proportional to V SENSE. 6 FB TOP VIEW RS+ RS- SHDN GND MAX9919 MAX992 4 EP* 8 SOIC-EP *EXPOSED PAD. CONNECT EP TO SOLID GROUND FOR PROPER THERMAL AND ELECTRICAL PERFORMANCE V CC REFIN FB OUT Pin Configuration Pin Description Feedback Input. Connect FB to a resistive-divider network to set the gain for the and MAX992. See the Adjustable Gain (/MAX992) section for more information. Leave FB unconnected for the MAX9919 for proper operation. /MAX9919/MAX992 7 REFIN Reference Input. Set REFIN to V CC /2 for bidirectional operation. Set REFIN to GND for unidirectional operation. 8 V CC 5V Supply Voltage Input. Bypass V CC to GND with.1μf capacitor. EP Exposed Pad. Connect to a large-area contiguous ground plane for improved power dissipation. Do not use as the only ground connection for the part. Detailed Description The /MAX9919/MAX992 are single-supply, high-accuracy uni-/bidirectional current-sense amplifiers with a high common-mode input range that extends from -2V to +75V. The /MAX9919/MAX992 s input stage utilizes a pair of level shifters allowing a wide common-mode operating range when measuring the voltage drop (V SENSE ) across the current-sense resistor. The first level shifter accommodates the upper commonmode operating range from +2V to +75V. When the common-mode voltage falls below +2V, the second level shifter is used to accommodate negative voltages down to -2V. The level shifters translate V SENSE to an internal reference voltage where it is then amplified with an instrumentation amplifier. The instrumentation amplifier configuration provides high precision with input offset voltages of 4μV (max). Indirect feedback of the instrumentation amplifier allows the gain to be adjusted with an external resistive-divider network on the /MAX992. The MAX9919 is a fixed gain device available with laser-trimmed resistors for gains of 45V/V (MAX9919F) and 9V/V (MAX9919N). The /MAX9919 operate with a full-scale sense voltage of 5mV. The input stage of the MAX992 provides an attenuation factor of 4, enabling a full-scale sense voltage of 2mV. 13

14 -2V to +75V Input Range, Precision /MAX9919/MAX992 Uni-/Bidirectional Operation The /MAX9919/MAX992 support both unidirectional and bidirectional operation. The devices operate in unidirectional mode with V REFIN = V GND. The output is then referenced to ground and the output voltage V OUT is proportional to the positive voltage drop (V SENSE ) from RS+ to RS- (Figure 1). I DISCHARGE 5V V CC SHDN RS+ R SENSE MAX9919N GND RS- OUT REFIN TO ADC LOAD The /MAX9919 operate in bidirectional mode by application of a low-source impedance reference voltage in the V to V CC - 1.9V range, (typically V CC /2), to REFIN. For the MAX992, the reference voltage range is V to V CC - 2.4V (typically V CC /2). The output voltage V OUT relative to V REFIN is then proportional to the ±V SENSE voltage drop from RS+ to RS- (Figure 2). V OUT 3.6V 2.7V 1.8V.9V 1mV 2mV DISCHARGE CURRENT 2mV G = 9V/V 3mV V SENSE Figure 1. Unidirectional Operation V OUT - V REFIN G = 9V/V 1.8V I DISCHARGE R SENSE I CHARGE RS+ RS- LOAD.9V DISCHARGE CURRENT 5V V CC MAX9919N OUT TO ADC -2mV -1mV 1mV 2mV V SENSE SHDN GND REFIN 2.5V CHARGE CURRENT -.9V -1.8V Figure 2. Bidirectional Operation 14

15 -2V to +75V Input Range, Precision Shutdown Mode Drive SHDN high to enter low-power shutdown mode. In shutdown mode, the /MAX9919/MAX992 draw.5μa (typ) of quiescent current. Adjustable Gain (/MAX992) The /MAX992 feature externally adjustable gain set by a resistive-divider network circuit using resistors R1 and R2 (see the Functional Diagram). The gain frequency compensation is set for a minimum gain of 3V/V for the and 7.5V/V for the MAX992. The gain G for the /MAX992 is given by the following equation: and R2 G = + 1 R 1 R2 1+ R1 G = 4 ( for ) ( for MAX992) Applications Information Component Selection 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 G where V SENSE is the full-scale sense voltage, 5mV for the /MAX9919, or 2mV for the MAX992 and G is the gain of the device. G is externally adjustable for the /MAX992. The MAX9919 has a fixed gain version of 45V/V (MAX9919F) or 9V/V (MAX9919N). In unidirectional applications (V REFIN = V), select the gain of the /MAX992 to utilize the full output range between GND and V CC. In bidirectional applications (V REFIN = V CC /2), select the gain to allow an output voltage range of ±V CC /2. V OUT must be at least 1mV from either rail to achieve the rated gain accuracy. Sense Resistor, R SENSE Choose R SENSE based on the following criteria: 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. In the linear region (1mV < V OUT < V CC - 1mV), there are two components to accuracy: input offset voltage (V OS ) and gain error (GE). Use the linear equation to calculate total error: V OUT = (G ± GE) x (V SENSE ±V OS ) For best performance, select R SENSE to provide approximately 5mV (/MAX9919) or 2mV (MAX992) of sense voltage for the full-scale current in each application. Sense resistors of 5mΩ to 1mΩ are available with 1% accuracy or better. 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 /MAX9919/MAX992 allows the use of small sense resistors to reduce power dissipation and reduce hot spots. Inductance: Keep inductance low if I SENSE has a large high-frequency component by using resistors with low inductance value. Power-Supply Bypassing and Grounding Bypass the /MAX9919/MAX992 s V CC to ground with a.1μf capacitor. Grounding these devices requires no special precautions; follow the same cautionary steps that apply to the rest of the system. High-current systems can experience large voltage drops across a ground plane, and this drop may add to or subtract from V OUT. Using a differential measurement between OUT and REFIN prevents this problem. For highest current-measurement accuracy, use a single-point star ground. Connect the exposed pad to a solid ground to ensure optimal thermal performance. /MAX9919/MAX992 15

16 -2V to +75V Input Range, Precision /MAX9919/MAX992 5mV (typ) 5mV (typ) MAX992 2mV (typ) RS+ R SENSE RS- I LOAD RS+ R SENSE RS- MAX9919F INPUT INPUT STAGE/ LEVEL SHIFTER SHDN MAX992 INPUT INPUT STAGE/ LEVEL SHIFTER V CC GND V CC A R2 R1 FIXED GAIN G = 45V/V OR 9V/V A Functional Diagram OUT FB REFIN OUT R2 FB R1 REFIN I LOAD ADJUSTABLE GAIN SHDN GND GAIN IS SET BY EXTERNAL RESISTORS, R1 AND R2 G = [1+(R2/R1)] FOR G = [1+(R2/R1)]/4 FOR MAX992 PROCESS: BiCMOS Chip Information 16

17 -2V to +75V Input Range, Precision Package Information For the latest package outline information and land patterns (footprints), 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. 8 SOIC-EP S8E L, SOIC EXP. PAD.EPS /MAX9919/MAX992 17

18 -2V to +75V Input Range, Precision /MAX9919/MAX992 REVISION NUMBER REVISION DATE DESCRIPTION Revision History PAGES CHANGED 1/9 Initial release 1 1/1 Updated Functional Diagram /1 Added automotive qualified part 1 3 6/11 Added MAX992ASA/V+ to data sheet 1 4 7/11 Added automotive qualified parts for the MAX9919NASA/V+ and the MAX992ASA/V+ 1 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. 18 Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.