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19-5015; Rev 0; 11/09
KIT ATION EVALU BLE AVAILA
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
General Description Features
o -20V to +75V Input Common-Mode Voltage Range o 400V (max) Input Offset Voltage o 0.6% (max) Gain Accuracy Error o Uni- or Bidirectional Current Sensing o Reference Input for Bidirectional OUT o 120kHz, -3dB Bandwidth (MAX9919N) o Single-Supply Operation (4.5V to 5.5V) o 1mA Supply Current o 0.5A (typ) Shutdown Current o Rail-to-Rail Output o -40C to +125C Automotive Temperature Range
MAX9918/MAX9919/MAX9920
The MAX9918/MAX9919/MAX9920 are single-supply, high-accuracy current-sense amplifiers with a high input common-mode range that extends from -20V 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 MAX9918/MAX9920 feature adjustable gain set by an external resistive-divider network. The MAX9919 features fixed gains of 45V/V (MAX9919F) and 90V/V (MAX9919N). The MAX9918/MAX9919/MAX9920 operate as unidirectional amplifiers when VREFIN = GND and as bidirectional amplifiers when VREFIN = VCC/2. The MAX9920 attenuates the input signal by a factor of 4 at the input level-shifting stage allowing the device to sense voltages up to 200mV (unidirectional operation) or 100mV (bidirectional operation). The MAX9918/MAX9919/MAX9920 operate with a single 5V supply voltage, are fully specified over the -40C to +125C automotive temperature range, and are available in an 8-pin SOIC package.
Ordering Information/ Selector Guide
PART MAX9918ASA+ MAX9919FASA+ MAX9919NASA+ MAX9920ASA+ VSENSE (mV) 50 50 50 200 GAIN (V/V) Adjustable 45 90 Adjustable PIN-PACKAGE 8 SOIC-EP* 8 SOIC-EP* 8 SOIC-EP* 8 SOIC-EP*
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
Note: All devices operate over the -40C to +125C temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad.
Typical Operating Circuit
VBATT VCC VCC
1A RSENSE M
2B
MAX9918 MAX9920
A
OUT R2
ADC
RS+ INPUT STAGE LEVEL SHIFTER
FB R1 REFIN ADJUSTABLE GAIN SHDN GND GND REF C
RS2B 1B
________________________________________________________________ Maxim Integrated Products
1
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.
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V RS+, RS- to GND (VCC = 5V) ..................................-30V to +80V RS+, RS- to GND (VCC = 0V) .............-15V to +80V (15 minutes) Differential Input Voltage (VRS+ - VRS-) (MAX9918/MAX9919).................................15V (Continuous) Differential Input Voltage (VRS+ - VRS-) (MAX9920) .............................5V (Continuous) REFIN, FB, OUT to GND.............................-0.3V to (VCC + 0.3V) SHDN to GND.........................................................-0.3V to +20V Output Short Circuit to VCC or GND...........................Continuous Continuous Current into Any Pin (Not to exceed package power dissipation) ................20mA Continuous Power Dissipation (TA = +70C) 8-Pin SOIC-EP (derate 24.4mW/C above +70C) .1951.2mW** SOIC Package Junction-to-Ambient Thermal Resistance (JA) (Note 1)...............................41C/W Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Reflow Soldering Temperature ........................................+260C Lead Temperature (soldering, 10s) .................................+300C
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.
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 www.maxim-ic.com/thermal-tutorial. **As per JEDEC51 Standard (multilayer board).
ELECTRICAL CHARACTERISTICS
(VCC = 5V, VRS+ = VRS- = +14V, VSENSE = (VRS+ - VRS-) = 0V, VSHDN = VGND = 0V, VREFIN = VCC/2, RL = 100k; for MAX9918, AV = 90V/V, R2/R1 = 89k/1k; for MAX9920, AV = 20V/V, R2/R1 = 79k/1k; TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS VRS+ = VRS- = +14V, VREFIN = 0V MAX9918 VRS+ = VRS- = -2V, VREFIN = 0V VRS+ = VRS- = +14V, VREFIN = 0V Input Offset Voltage (Note 2) VOS MAX9919_ VRS+ = VRS- = -2V, VREFIN = 0V VRS+ = VRS- = +14V, VREFIN = 0V MAX9920 VRS+ = VRS- = -2V, VREFIN = 0V TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C 0.10 0.48 0.11 0.18 0.08 MIN TYP 0.14 MAX 0.4 0.7 0.4 1.3 0.4 0.9 0.4 1.0 1.2 3.0 0.9 3.5 mV UNITS
2
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VRS+ = VRS- = +14V, VSENSE = (VRS+ - VRS-) = 0V, VSHDN = VGND = 0V, VREFIN = VCC/2, RL = 100k; for MAX9918, AV = 90V/V, R2/R1 = 89k/1k; for MAX9920, AV = 20V/V, R2/R1 = 79k/1k; TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1
PARAMETER SYMBOL MAX9918 Input Offset Voltage Drift (Note 3) VOSD MAX9919_ MAX9920 Common-Mode Range Common-Mode Rejection Ratio (Note 3) VCM CONDITIONS VRS+ = VRS- = +14V VRS+ = VRS- = -2V VRS+ = VRS- = +14V VRS+ = VRS- = -2V VRS+ = VRS- = +14V VRS+ = VRS- = -2V -20 80 96 72 86 175 250 0 -20V VCM +75V, VSHDN = VCC = 5V VRS+ = VRS- = +14V, +75V, VCC = 0V MAX9918, MAX9919_ Input Resistance MAX9920 Full-Scale Sense Voltage (Note 4) VSENSE Inferred from gain error test MAX9918, MAX9920 Gain (Notes 2, 4) G MAX9919F MAX9919N Minimum Adjustable Gain GADJ MAX9918 MAX9920 Common mode Differential Common mode Differential MAX9918, MAX9919_ MAX9920 300 715 330 224 50 200 Adj 45 90 30 7.5 V/V V/V 8 30 30 A A A A k k mV dB -2V VCM +14V -20V VCM +75V -2V VCM +14V -20V VCM +75V TA = +25C TA = -40C to +125C MIN TYP 1.2 3.3 1.8 1.8 2.4 8.8 +75 V V/C MAX UNITS
MAX9918/MAX9919/MAX9920
Inferred from CMRR tests MAX9918, MAX9919
CMRR MAX9920
Input Bias Current Input Offset Current Input Leakage Current in Shutdown Input Leakage Current
IRS+, IRS(IRS+ - IRS-)
-20V VCM +75V
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3
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VRS+ = VRS- = +14V, VSENSE = (VRS+ - VRS-) = 0V, VSHDN = VGND = 0V, VREFIN = VCC/2, RL = 100k; for MAX9918, AV = 90V/V, R2/R1 = 89k/1k; for MAX9920, AV = 20V/V, R2/R1 = 79k/1k; TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1
PARAMETER SYMBOL CONDITIONS TA = +25C, VREFIN = 0V TA = -40C to +125C, VREFIN = 0V TA = +25C TA = -40C to +125C 0.13 0.02 MIN TYP 0.08 MAX 0.6 UNITS
VRS+ = VRS- = +14V MAX9918 VRS+ = VRS- = -2V, VREFIN = 0V
1.2 0.6 1.0 0.45 1.2 0.10 0.45 0.9 0.16 0.6 1.2 0.11 0.6 1.0 0.29 1.0 1.7 0.24 1.0 1.7 5 15 10 mV 40 10 mV 40 mA VCC 1.9 V VCC 2.4 nA %
MAX9919F Gain Error (Note 2) GE
VRS+ = VRS- = TA = +25C +14V, VREFIN = TA = -40C to 0V +125C VRS+ = VRS- = -2V, VREFIN = 0V TA = +25C TA = -40C to +125C
MAX9919N
VRS+ = VRS- = TA = +25C +14V, VREFIN = TA = -40C to 0V +125C VRS+ = VRS- = -2V, VREFIN = 0V TA = +25C TA = -40C to +125C
MAX9920
VRS+ = VRS- = TA = +25C +14V, VREFIN = TA = -40C to 0V +125C VRS+ = VRS- = -2V, VREFIN = 0V TA = +25C TA = -40C to +125C
FB Input Bias Current Output-Voltage High (Note 4)
IFB
MAX9918, MAX9920 RL = 100k to GND RL = 10k to GND RL = 100k to VCC RL = 10k to VCC
Output-Voltage Low (Note 4)
Short-Circuit Current Output Resistance
VSENSE = 200mV for MAX9918, MAX9919_, VCC - VOH VSENSE = 400mV for MAX9920 VSENSE = -200mV for MAX9918, MAX9919_, VOL VSENSE = -400mV for MAX9920 OUT shorted to VCC ISC OUT shorted to GND ROUT
3 12 3 10 44 41 0.1 VCC /2 VCC /2
MAX9918, MAX9919_ REFIN Voltage Range Inferred from REFIN CMRR test MAX9920
0 0
4
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VRS+ = VRS- = +14V, VSENSE = (VRS+ - VRS-) = 0V, VSHDN = VGND = 0V, VREFIN = VCC/2, RL = 100k; for MAX9918, AV = 90V/V, R2/R1 = 89k/1k; for MAX9920, AV = 20V/V, R2/R1 = 79k/1k; TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1
PARAMETER REFIN Common-Mode Rejection Ratio SYMBOL CONDITIONS MAX9918, MAX9919_ REFINCMRR MAX9920 REFIN Current SHDN Logic-High SHDN Logic-Low SHDN Logic-Input Current Supply Voltage Range Power-Supply Rejection Ratio (Note 3) VCC PSRR IREFIN VIH VIL 0V VSHDN VCC Inferred from PSRR test MAX9918, MAX9919_ MAX9920 VRS+ = VRS- = +14V Supply Current ICC VRS+ = VRS- = -2V Shutdown Supply Current ICC_SHDN VSHDN = VCC = 5V MAX9918, VSENSE = 50mV Small-Signal -3dB Bandwidth BW MAX9919F, VSENSE = 50mV MAX9919N, VSENSE = 50mV MAX9920, VSENSE = 200mV MAX9918 Slew Rate SR MAX9919F MAX9919N MAX9920 MAX9918 MAX9919F 1% Settling Time from VSENSE Step MAX9919N MAX9920 VSENSE = 5mV to 50mV step VSENSE = 50mV to 5mV step VSENSE = 5mV to 50mV step VSENSE = 50mV to 5mV step VSENSE = 5mV to 50mV step VSENSE = 50mV to 5mV step VSENSE = 20mV to 200mV step VSENSE = 200mV to 20mV step 4.5V VCC 5.5V 4.5V VCC 5.5V TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C 0.5 75 250 120 230 0.6 0.9 3.0 1.5 12 7 3.5 2.5 3.5 3 5 3 s V/s kHz 1.0 4.5 74 68 103 100 0.7 1.2 1.5 1.6 2.2 10 A mA 0V VREFIN (VCC - 1.9V) 0V VREFIN (VCC - 2.4V) MIN 82 75 TYP 103 dB 90 100 100 2.0 0.8 5 5.5 A V V A V dB MAX UNITS
MAX9918/MAX9919/MAX9920
MAX9918, MAX9919_, VRS+ = VRS- = 50mV MAX9920, VRS+ = VRS- = 200mV
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5
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, VRS+ = VRS- = +14V, VSENSE = (VRS+ - VRS-) = 0V, VSHDN = VGND = 0V, VREFIN = VCC/2, RL = 100k; for MAX9918, AV = 90V/V, R2/R1 = 89k/1k; for MAX9920, AV = 20V/V, R2/R1 = 79k/1k; TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1
PARAMETER SYMBOL CONDITIONS MAX9918, VSENSE = 50mV MAX9919F, VSENSE = 50mV MAX9919N, VSENSE = 50mV MAX9920, VSENSE = 200mV VCM = -2V to +14V step VCM = +14V to -2V step VCM = -2V to +14V step VCM = +14V to -2V step VCM = -2V to +14V step VCM = +14V to -2V step VCM = -2V to +14V step VCM = +14V to -2V step MIN TYP 2.5 0.5 2.5 0.5 3.5 3.5 0.25 2.5 4.5 5 6 5 50 60 174 pF nV/Hz s s MAX UNITS
1% Settling Time from VCM Step
MAX9918, VSENSE = 50mV, 1% settling Power-Up Time MAX9919F, VSENSE = 50mV, 1% settling MAX9919N, VSENSE = 50mV, 1% settling MAX9920, VSENSE = 200mV, 1% settling Maximum Capacitive Load Stability Input Referred Noise Voltage Density en No sustained oscillations (Note 5) 10kHz MAX9918, MAX9919_ MAX9920
Note 1: All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Note 2: VOS is extrapolated from two point gain error tests. Measurements are made at VSENSE = 5mV and 50mV for MAX9918/MAX9919N/MAX9919F, and VSENSE = 20mV and 200mV for MAX9920. Note 3: Extrapolated VOS as described above in Note 2 is used to calculate VOS drift, CMRR, and PSRR. Note 4: OUT should be 100mV away from either rail to achieve rated accuracy, or limited by a VSENSE of 50mV for the MAX9918/MAX9919N/MAX9919F and 200mV for the MAX9920. Note 5: Not production tested. Guaranteed by design.
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Typical Operating Characteristics
(VCC = 5V, TA = +25C, unless otherwise noted.)
VOS (VRS+ = +14V)
0.45 0.40 0.35 N (%) N (%) 0.30 0.25 0.20 0.15 0.10 0.05 0 -400 -320 -240-160 -80 0 80 160 240 320 400 OFFSET VOLTAGE (FV) 0 -4 -3 -2 -1 0 1 2 3 4 0.10 0.05
MAX9918 toc01
MAX9918/MAX9919/MAX9920
VOS DRIFT (VRS+ = +14V)
MAX9918 toc02
VOS (VRS+ = -2V)
0.30 0.25 N (%) 0.20 0.15 0.10 0.05 0 -400 -320 -240-160 -80 0 80 160 240 320 400
MAX9918 toc03
0.50
0.30 0.25 0.20 0.15
0.35
OFFSET VOLTAGE (FV/C)
OFFSET VOLTAGE (FV)
VOS DRIFT (VRS+ = -2V)
MAX9918 toc04
VOS vs. VCM
400 300 200
MAX9918 toc05
VOS vs. VCC
100 75 50 VOS (FV) 25 0 -25 -50 -75 -100 MAX9918ASA VCC = 5V VREF = GND VCM = -2V VCM = 14V
MAX9918 toc06
0.45 0.40 0.35 0.30 N (%) 0.25 0.20 0.15 0.10 0.05 0 -10 -8 -6 -4 -2 0 2 4 6 8 10 OFFSET VOLTAGE (FV/C)
500 TA = -40C TA = +25C
125
VOS (uV)
100 0 -100 -200 -300 -400 -500 -20 -10 0 10 20 30 40 50 60 70 80 VCM (V) MAX9918ASA VCC = 5V VREF = GND TA = +125C
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 VCC (V)
GAIN ERROR (VRS+ = +14V, MAX9919F, AV = +45V/V)
MAX9918 toc07
GAIN ERROR (VRS+ = +14V, MAX9919N, AV = +90V/V)
0.7 0.6
MAX9918 toc08
GAIN ERROR (VRS+ = -2V, MAX9919F, AV = +45V/V)
MAX9918 toc09
0.6 0.5 0.4 N (%)
0.8
0.6 0.5 0.4 N (%) 0.3 0.2 0.1 0
0.5 N (%) 0.4 0.3 0.2
0.3 0.2 0.1 0
0.1 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 GAIN ERROR (%) 0 0.4 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 GAIN ERROR (%) 0.4
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 GAIN ERROR (%)
0.3
0.4
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
Typical Operating Characteristics (continued)
(VCC = 5V, TA = +25C, unless otherwise noted.)
GAIN ERROR (VRS+ = -2V, MAX9919N, AV = +90V/V)
MAX9918 toc10
GAIN ERROR vs. VCM
1.6 1.2 0.8 GE (%) 0.4 0 -0.4 -0.8 -1.2 -1.6 -2.0 MAX9918ASA VCC = 5V VREF = GND -20 -10 0 TA = -40NC TA = +125NC TA = +25NC
MAX9918 toc11
0.6 0.5 0.4 N (%) 0.3 0.2 0.1 0
2.0
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 GAIN ERROR (%)
0.3
0.4
10 20 30 40 50 60 70 80 VCM (V)
GAIN ERROR vs. VCC
MAX9918 toc12
0.4 0.3 GAIN ERROR (%) 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 4.5 4.7 4.9 5.1 VCC (V) 5.3 VCM = 14V VCM = -2V
0.20 0.15 LINEARITY (%) 0.10 0.05 0 TA = +125C TA = +25C TA = -40C
VCM = -2V VCC = 5V VREFIN = VCC/2 AV = 90V/V BIDIRECTIONAL
-0.05 -0.10 -0.15 -0.20
-0.25
5.5
-30
-20
-10
0 10 VSENSE (mV)
20
30
LINEARITY vs. VSENSE
0.08 0.06 LINEARITY (%) 0.04 0.02 0 TA = +125C TA = +25C TA = -40C VCM = +14V VCC = 5V VREFIN = VCC/2 AV = 90V/V BIDIRECTIONAL
MAX9918 toc14
LINEARITY vs. VSENSE
0.08 0.06 LINEARITY (%) 0.04 0.02 0 TA = +125C TA = +25C VCM = -2V VCC = 5V VREFIN = GND TA = -40C AV = 90V/V UNIDIRECTIONAL
MAX9918 toc15
0.10
0.10
-0.02 -0.04 -0.06 -0.08
-0.02 -0.04 -0.06 -0.08 -0.10
-0.10 -30 -20 -10 0 VSENSE (mV) 10 20 30
0
10
20
30 40 50 VSENSE (mV)
60
70
80
8
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MAX9918 toc13
0.5
LINEARITY vs. VSENSE
0.25
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Typical Operating Characteristics (continued)
(VCC = 5V, TA = +25C, unless otherwise noted.)
MAX9918/MAX9919/MAX9920
LINEARITY vs. VSENSE
0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0 -0.02 -0.04 -0.06 -0.08 -0.10
MAX9918 toc16
LINEARITY vs. VSENSE
0.20 0.15 LINEARITY (%) 0.10 0.05 0 TA = +125C TA = -40C TA = +25C VCM = -2V VCC = 5V VREFIN = VCC/2 AV = 30V/V BIDIRECTIONAL
MAX9918 toc17
0.25
LINEARITY (%)
VCM = +14V VCC = 5V VREFIN = GND AV = 90V/V UNIDIRECTIONAL TA = +25C TA = -40C
-0.05 -0.10 -0.15 -0.20
TA = +125C
-0.25 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 VSENSE (mV) -100 -80 -60 -40 -20 0 20 40 60 80 100 VSENSE (mV)
LINEARITY vs. VSENSE
MAX9918 toc18
VOUT - VREFIN vs. VSENSE
6 6 5 5 4 4 3 3 2 2 1 1 0 -1 -1 -2V VCM: SOLID LINE 14V VCM: DASHED LINE
MAX9918 toc19
0.10 0.08 0.06 LINEARITY (%) 0.04 0.02 0 TA = +25C TA = -40C TA = +125C VCM = +14V VCC = 5V VREFIN = VCC/2 AV = 30V/V BIDIRECTIONAL
-0.02 -0.04 -0.06 -0.08 -0.10
VOUT - VREFIN (V)
MAX9918, VREFIN = 0V UNIDIRECTIONAL, GAIN = 90V/V -20 -10 0 10 20 30 40 50 60 70 80
VSENSE (mV)
-100 -80 -60 -40 -20 0 20 40 60 80 100 VSENSE (mV)
VOUT - VREFIN vs. VSENSE
3 3 2 2 1 1 0 -1 -1 -2 -2 -3 -3
MAX9918 toc20
VOH/VOL vs. IOH
VCM = +14V 300 VOH AND VOL (mV) 250 200 150 100 VOL 50 0 VCC - VOH
MAX9918 toc21
-2V VCM: SOLID LINE 14V VCM: DASHED LINE
350
VOUT - VREFIN (V)
MAX9918, VREFIN = VCC/2 BIDIRECTIONAL, GAIN = 90V/V 10 -40 -30 -20 -10 0 VSENSE (mV) 20 30 40
0
1
2
3
456 IOH (mA)
7
8
9
10
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
Typical Operating Characteristics (continued)
(VCC = 5V, TA = +25C, unless otherwise noted.)
ICC vs. VCC
MAX9918 toc22
ICC vs.VCM
1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 TA = +125NC VSENSE = 0V (DASH) VSENSE + 50mV (SOLID
MAX9918 toc23
IBIAS vs. VCM
80 60 40 20 0 -20 -40 -60 -80 -100 MAX9918 VCC = 5V -20 -10 0 10 20 30 40 50 60 70 80 VCM (V)
MAX9918 toc24
1.0 0.9 0.8 0.7 ICC (mA) 0.6 0.5 0.4 0.3 0.2 0.1 0 VSENSE = 0V VCM = 14V VCM = -2V
100
TA = +25NC
TA = -40NC
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 VCC (V)
-20 -10 0
10 20 30 40 50 60 70 80 VCM (V)
INPUT LEAKAGE CURRENT vs. VCM
20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50
MAX9918 toc25
DIFFERENTIAL RIN vs. VCM
MAX9918 toc26
IBAIS (FA)
ICC (mA)
GAIN vs. FREQUENCY
40 30 20 GAIN (dB) 10 0 -10 -20 -30 MAX9918 VCM = 14V GAIN = 90V/V 0.01 0.1 1 FREQUENCY (MHz) 10
MAX9918 toc27
1000 900 800 DIFFERENTIAL RIN (I) 700 600 500 400 300 200 100 0
50
INPUT LEAKAGE CURRENT (FA)
TA = +25NC TA = -40NC
TA = +125NC IN+ - IN- = 50mV VCC = VSHDN = 0V VREFIN = 0V -20 0 20 40 VCM (V) 60 80
-20
-5
10
25 VCM (V)
40
55
70
-40 0.001
GAIN vs. FREQUENCY
MAX9918 toc28
GAIN vs. FREQUENCY
MAX9918 toc29
PSRR vs. FREQUENCY
-20 -40 PSRR (dB) -60 -80 -100 MAX9918 VCM = 14V VSENSE = 50mV
MAX9918 toc30
40 30 20 10
10 0 -10 -20 GAIN (dB) -30 -40 -50 -60 -70
MAX9918 VCM = 14V GAIN = 90V/V
0
GAIN (dB)
0 -10 -20 -30 -40 -50 MAX9920 VCM = 14V GAIN = 20V/V 0.01 0.1 FREQUENCY (MHz) 1 10
VCM = -2V
-80 -90 -100 0.001 0.01 VCM = 14V 0.1 1 FREQUENCY (MHz) 10 100
-120 -140 10 100 0.0001 0.001 0.01 0.1 1 FREQUENCY (kHz)
-60 0.001
1k
10k
10
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-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Typical Operating Characteristics (continued)
(VCC = 5V, TA = +25C, unless otherwise noted.)
SMALL-SIGNAL TRANSIENT (GAIN = 45V/V) SMALL-SIGNAL TRANSIENT (GAIN = 90V/V)
MAX9918/MAX9919/MAX9920
MAX9918 toc31
MAX9918 toc32
5mV/div
5mV/div
50mV/div
MAX9918, VCM = 14V VSENSE = 10mV TO 15mV 10Fs/div
100mV/div
MAX9918, VCM = 14V VSENSE = 10mV TO 15mV 10Fs/div
LARGE-SIGNAL TRANSIENT (GAIN = 45V/V)
MAX9918 toc33
LARGE-SIGNAL TRANSIENT (GAIN = 90V/V)
MAX9918 toc34
50mV/div
50mV/div
500mV/div
MAX9918, VCM = 14V VSENSE = 0V TO 50mV 10Fs/div
1V/div
MAX9918, VCM = 14V VSENSE = 0 TO 50mV 10Fs/div
COMMON-MODE STEP RESPONSE
MAX9918 toc35
OUTPUT RESPONSE TO COMMON-MODE TRANSIENT
MAX9918 toc36
MAX9918, VCM = 14V SSENSE = PS (50mV)
VCM 50V/div
10V/div 1V/div
0
OUTPUT AC-COUPLED FULL SCALE AT THE INPUT
VOUT 100mV/div
10Fs/div
4s/div
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11
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
Typical Operating Characteristics (continued)
(VCC = 5V, TA = +25C, unless otherwise noted.)
SHUTDOWN ON/OFF DELAY
5V/div
MAX9918 toc37
POWER-UP TIME
MAX9918 toc38
5V/div
2V/div 1V/div MAX9918, VCM = 14V VSENSE = PS (50mV) 4Fs/div MAX9918, VCM = 14V VSENSE = PS (50mV) 4Fs/div
OUTPUT OVERDRIVE RECOVERY (30V/V)
MAX9918 toc39
OUTPUT OVERDRIVE RECOVERY (90V/V)
MAX9918 toc40
MAX9918, VCM = 14V VSENSE = 2 x PS
200mV/div
50mV/div
2V/div 4Fs/div
2V/div
MAX9918, VCM = 14V VSENSE = 2 x PS 4Fs/div
12
______________________________________________________________________________________
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Pin Configuration
TOP VIEW
+ RS+ 1 RS- 2 SHDN 3 MAX9918 MAX9919 MAX9920 EP* 8 VCC 7 REFIN 6 FB
MAX9918/MAX9919/MAX9920
GND 4
5 OUT
8 SOIC-EP
*EXPOSED PAD. CONNECT EP TO SOLID GROUND FOR PROPER THERMAL AND ELECTRICAL PERFORMANCE.
Pin Description
PIN 1 2 3 4 5 6 NAME RS+ RSSHDN GND OUT FB FUNCTION Positive Current-Sensing Input. Power side connects to external sense resistor. Negative Current-Sensing Input. Load side connects to external sense resistor. Active-High Shutdown Input. Connect to GND for normal operation. Ground Current-Sense Output. VOUT is proportional to VSENSE. Feedback Input. Connect FB to a resistive-divider network to set the gain for the MAX9918 and MAX9920. See the Adjustable Gain (MAX9918/MAX9920) section for more information. Leave FB unconnected for the MAX9919 for proper operation. Reference Input. Set REFIN to VCC/2 for bidirectional operation. Set REFIN to GND for unidirectional operation. 5V Supply Voltage Input. Bypass VCC to GND with 0.1F capacitor. 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.
7 8 --
REFIN VCC EP
Detailed Description
The MAX9918/MAX9919/MAX9920 are single-supply, high-accuracy uni-/bidirectional current-sense amplifiers with a high common-mode input range that extends from -20V to +75V. The MAX9918/MAX9919/MAX9920's input stage utilizes a pair of level shifters allowing a wide common-mode operating range when measuring the voltage drop (VSENSE) 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 -20V.
The level shifters translate VSENSE 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 400V (max). Indirect feedback of the instrumentation amplifier allows the gain to be adjusted with an external resistive-divider network on the MAX9918/MAX9920. The MAX9919 is a fixed gain device available with laser-trimmed resistors for gains of 45V/V (MAX9919F) and 90V/V (MAX9919N). The MAX9918/MAX9919 operate with a full-scale sense voltage of 50mV. The input stage of the MAX9920 provides an attenuation factor of 4, enabling a full-scale sense voltage of 200mV.
______________________________________________________________________________________
13
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
Uni-/Bidirectional Operation
The MAX9918/MAX9919/MAX9920 support both unidirectional and bidirectional operation. The devices operate in unidirectional mode with V REFIN = GND. The output is then referenced to ground and the output voltage VOUT is proportional to the positive voltage drop (VSENSE) from RS+ to RS- (Figure 1). The MAX9918/MAX9919 operate in bidirectional mode by application of a low-source impedance reference voltage in the 0V to VCC - 1.9V range, (typically VCC/2), to REFIN. For the MAX9920, the reference voltage range is 0V to VCC - 2.4V (typically VCC/2). The output voltage V OUT relative to V REFIN is then proportional to the VSENSE voltage drop from RS+ to RS- (Figure 2).
VOUT
3.6V IDISCHARGE RSENSE 2.7V RS+ RSLOAD
G = 90V/V
MAX9919N
5V VCC OUT TO ADC
1.8V
DISCHARGE CURRENT
SHDN GND
REFIN
0.9V
0
10mV
20mV
20mV
30mV
VSENSE
Figure 1. Unidirectional Operation
VOUT - VREFIN G = 90V/V 1.8V IDISCHARGE RSENSE ICHARGE DISCHARGE CURRENT 0.9V RS+ RSLOAD
MAX9919N
5V VCC OUT TO ADC -20mV -10mV 0 10mV 20mV VSENSE
SHDN GND
REFIN
2.5V
CHARGE CURRENT
-0.9V
-1.8V
Figure 2. Bidirectional Operation
14 ______________________________________________________________________________________
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Shutdown Mode
Drive SHDN high to enter low-power shutdown mode. In shutdown mode, the MAX9918/MAX9919/MAX9920 draw 0.5A (typ) of quiescent current.
Adjustable Gain (MAX9918/MAX9920)
The MAX9918/MAX9920 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 30V/V for the MAX9918 and 7.5V/V for the MAX9920. The gain G for the MAX9918/MAX9920 is given by the following equation: R2 G = 1+ (for MAX9918) R1 and R2 1 + R1 G= (for MAX9920) 4
Sense Resistor, RSENSE Choose RSENSE based on the following criteria: Accuracy: A high RSENSE 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 (100mV < V OUT < V CC - 100mV), there are two components to accuracy: input offset voltage (VOS) and gain error (GE). Use the linear equation to calculate total error:
VOUT = (G GE) x (VSENSE VOS) For best performance, select R SENSE to provide approximately 50mV (MAX9918/MAX9919) or 200mV (MAX9920) of sense voltage for the full-scale current in each application. Sense resistors of 5m to 100m are available with 1% accuracy or better.
MAX9918/MAX9919/MAX9920
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 MAX9918/MAX9919/MAX9920 allows the use of small sense resistors to reduce power dissipation and reduce hot spots. Inductance: Keep inductance low if ISENSE has a large high-frequency component by using resistors with low inductance value.
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: VOUT = VSENSE x G where VSENSE is the full-scale sense voltage, 50mV for the MAX9918/MAX9919, or 200mV for the MAX9920 and G is the gain of the device. G is externally adjustable for the MAX9918/MAX9920. The MAX9919 has a fixed gain version of 45V/V (MAX9919F) or 90V/V (MAX9919N). In unidirectional applications (VREFIN = 0V), select the gain of the MAX9918/MAX9920 to utilize the full output range between GND and VCC. In bidirectional applications (VREFIN = VCC/2), select the gain to allow an output voltage range of VCC/2. VOUT must be at least 100mV from either rail to achieve the rated gain accuracy.
Power-Supply Bypassing and Grounding
Bypass the MAX9918/MAX9919/MAX9920's V CC to ground with a 0.1F 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 VOUT. Using a differential measurement between VOUT 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.
______________________________________________________________________________________
15
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers MAX9918/MAX9919/MAX9920
Functional Diagram
VCC
MAX9919F
A R2 RS+ 50mV (typ) RSENSE RSILOAD INPUT INPUT STAGE/ LEVEL SHIFTER R1
OUT
FB
REFIN FIXED GAIN G = 45V/V OR 90V/V
SHDN
GND VCC
MAX9918 MAX9920
A
OUT R2
MAX9918 50mV (typ) MAX9920 200mV (typ)
RS+ RSENSE RSILOAD ADJUSTABLE GAIN SHDN GND INPUT INPUT STAGE/ LEVEL SHIFTER
FB R1 REFIN
GAIN IS SET BY EXTERNAL RESISTORS, R1 AND R2 G = [1+(R2/R1)] FOR MAX9918 G = [1+(R2/R1)]/4 FOR MAX9920
Chip Information
PROCESS: BiCMOS
16
______________________________________________________________________________________
-20V to +75V Input Range, Precision Uni-/Bidirectional, Current-Sense Amplifiers
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 8 SOIC-EP PACKAGE CODE S8E+14 DOCUMENT NO. 21-0111
8L, SOIC EXP. PAD.EPS
MAX9918/MAX9919/MAX9920
PACKAGE OUTLINE 8L SOIC, .150" EXPOSED PAD
21-0111
C
1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17
(c) 2009 Maxim Integrated Products Maaxim is a registered trademark of Maxim Integrated Products, Inc.

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