View MAX408008_4432960.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-2562; Rev 1; 11/08
KIT ATION EVALU ILABLE AVA
76V, High-Side, Current-Sense Amplifiers with Voltage Output
General Description
The MAX4080/MAX4081 are high-side, current-sense amplifiers with an input voltage range that extends from 4.5V to 76V making them ideal for telecom, automotive, backplane, and other systems where high-voltage current monitoring is critical. The MAX4080 is designed for unidirectional current-sense applications and the MAX4081 allows bidirectional current sensing. The MAX4081 single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. The MAX4081 requires an external reference to set the zero-current output level (VSENSE = 0V). The charging current is represented by an output voltage from VREF to VCC, while discharge current is given from VREF to GND. For maximum versatility, the 76V input voltage range applies independently to both supply voltage (VCC) and common-mode input voltage (V RS+). High-side current monitoring does not interfere with the ground path of the load being measured, making the MAX4080/MAX4081 particularly useful in a wide range of high-voltage systems. The combination of three gain versions (5V/V, 20V/V, 60V/V = F, T, S suffix) and a user-selectable, external sense resistor sets the full-scale current reading and its proportional output voltage. The MAX4080/MAX4081 offer a high level of integration, resulting in a simple, accurate, and compact current-sense solution. The MAX4080/MAX4081 operate from a 4.5V to 76V single supply and draw only 75A of supply current. These devices are specified over the automotive operating temperature range (-40C to +125C) and are available in a space-saving 8-pin MAX(R) or SO package.
Features
Wide 4.5V to 76V Input Common-Mode Range Bidirectional or Unidirectional ISENSE Low-Cost, Compact, Current-Sense Solution Three Gain Versions Available 5V/V (MAX4080F/MAX4081F) 20V/V (MAX4080T/MAX4081T) 60V/V (MAX4080S/MAX4081S) 0.1% Full-Scale Accuracy Low 100V Input Offset Voltage Independent Operating Supply Voltage 75A Supply Current (MAX4080) Reference Input for Bidirectional OUT (MAX4081) Available in a Space-Saving, 8-Pin MAX Package
MAX4080/MAX4081
Ordering Information
PART MAX4080FAUA MAX4080FASA MAX4080TAUA MAX4080TASA MAX4080SAUA MAX4080SASA MAX4081FAUA MAX4081FASA MAX4081TAUA MAX4081TASA MAX4081SAUA MAX4081SASA TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO
Applications
Automotive (12V, 24V, or 42V Batteries) 48V Telecom and Backplane Current Measurement Bidirectional Motor Control Power-Management Systems Avalanche Photodiode and PIN-Diode Current Monitoring General System/Board-Level Current Sensing Precision High-Voltage Current Sources
Selector Guide appears at end of data sheet.
Pin Configurations
TOP VIEW
RS+ VCC N.C.
1 2
8 7
RSN.C. N.C. OUT
RS+ 1 VCC N.C. 2
8 7
RSREF1A REF1B OUT
MAX4080
3 6 5
MAX4081
3 6 5
GND 4
GND 4
MAX is a registered trademark of Maxim Integrated Products, Inc.
MAX/SO
MAX/SO
________________________________________________________________ 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.
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
ABSOLUTE MAXIMUM RATINGS
VCC to GND ............................................................-0.3V to +80V RS+, RS- to GND....................................................-0.3V to +80V OUT to GND.............-0.3V to the lesser of +18V or (VCC + 0.3V) REF1A, REF1B to GND (MAX4081 Only)....-0.3V to the lesser of +18V or (VCC + 0.3V) Output Short Circuit to GND.......................................Continuous Differential Input Voltage (VRS+ - VRS-) ...............................80V Current into Any Pin..........................................................20mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5mW/C above +70C) .............362mW 8-Pin SO (derate 5.88mW/C above +70C)................471mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C 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.
DC ELECTRICAL CHARACTERISTICS
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER Operating Voltage Range Common-Mode Range Supply Current Leakage Current Input Bias Current Full-Scale Sense Voltage (Note 4) SYMBOL VCC CMVR ICC IRS+, IRSIRS+, IRSVSENSE CONDITIONS Inferred from PSRR test Inferred from CMRR test (Note 3) VCC = VRS+ = 76V, no load VCC = VRS+ = 76V MAX4080F/MAX4081F MAX4080T/MAX4081T MAX4080S/MAX4081S MAX4080F/MAX4081F Gain AV MAX4080T/MAX4081T MAX4080S/MAX4081S Gain Accuracy AV VCC = VRS+ = 48V (Note 5) TA = +25C TA = -40C to +85C TA = TMIN to TMAX Input Offset Voltage Common-Mode Rejection Ratio Power-Supply Rejection Ratio VOS CMRR PSRR VCC = VRS+ = 48V (Note 6) TA = +25C TA = -40C to +85C TA = TMIN to TMAX VCC = 48V, VRS+ = 4.5V to 76V VRS+ = 48V, VCC = 4.5V to 76V MAX4080F/MAX4081F, VSENSE = 1000mV MAX4080T/MAX4081T, VSENSE = 250mV MAX4080S/MAX4081S, VSENSE = 100mV 0.15 0.27 V 100 100 124 122 0.1 MAX4080 MAX4081 MIN 4.5 4.5 75 103 0.01 5 1000 250 100 5 20 60 0.1 0.6 1 1.2 0.6 1 1.2 dB dB mV % V/V mV TYP MAX 76 76 190 190 2 12 UNITS V V A A A
VCC = 0V, VRS+ = 76V
OUT High Voltage
(VCC VOH)
VCC = 4.5V, VRS+ = 48V, VREF1A = VREF1B = 2.5V, IOUT (sourcing) = +500A (Note 8)
2
_______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS VCC = VRS+ = 48V, VREF1A = VREF1B = IOUT (sinking) = 10A 2.5V, VSENSE = IOUT (sinking) = -1000mV (for 100A MAX4081 only) Inferred from REF1A rejection ratio, VREF1A = VREF1B Inferred from REF1A rejection ratio, VREF1B = GND VCC = VRS+ = 48V, VSENSE = 0V, VREF1A = VREF1B = 1.5V to 6V VREF1A = 10V, VREF1B = GND, VCC = VRS+ = 48V (Note 2) VREF1B = GND 1.5 3 80 0.497 108 0.500 250 0.503 k MIN TYP 4 MAX 15 mV 23 55 6 12 V V dB UNITS
MAX4080/MAX4081
OUT Low Voltage
VOL
REF1A = REF1B Input Voltage Range (MAX4081 Only) REF1A Input Voltage Range (MAX4081 Only) REF1A Rejection Ratio (MAX4081 Only) REF/REF1A Ratio (MAX4081 Only) REF1A Input Impedance (MAX4081 Only)
(VREF GND) (VREF1A GND)
_______________________________________________________________________________________
3
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
AC ELECTRICAL CHARACTERISTICS
(VCC = VRS+ = 4.5V to 76V, VREF1A = VREF1B = 5V (MAX4081 only), VSENSE = (VRS+ - VRS-) = 0V, RLOAD = 100k, CLOAD = 20pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER Bandwidth OUT Settling Time to 1% of Final Value Capacitive-Load Stability Output Resistance Power-Up Time Saturation Recovery Time ROUT SYMBOL BW CONDITION VCC = VRS+ = 48V, VOUT = 2.5V MAX4080F/T/S MAX4081F/T/S MIN TYP 250 150 20 20 500 0.1 50 50 MAX UNITS kHz s pF s s
VSENSE = 10mV to 100mV VSENSE = 100mV to 10mV No sustained oscillations VSENSE = 100mV VCC = VRS+ = 48V, VSENSE = 100mV (Note 9) (Notes 9,10)
Note 1: All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Note 2: VREF is defined as the average voltage of VREF1A and VREF1B. REF1B is usually connected to REF1A or GND. VSENSE is defined as VRS+ - VRS-. Note 3: The common-mode range at the low end of 4.5V applies to the most positive potential at RS+ or RS-. Depending on the polarity of VSENSE and the device's gain, either RS+ or RS- can extend below 4.5V by the device's typical full-scale value of VSENSE. Note 4: Negative VSENSE applies to MAX4081 only. Note 5: VSENSE is: MAX4080F, 10mV to 1000mV MAX4080T, 10mV to 250mV MAX4080S, 10mV to 100mV MAX4081F, -500mV to +500mV MAX4081T, -125mV to +125mV MAX4081S, -50mV to +50mV Note 6: VOS is extrapolated from the gain accuracy test for the MAX4080 and measured as (VOUT - VREF)/AV at VSENSE = 0V, for the MAX4081. Note 7: VSENSE is: MAX4080F, 500mV MAX4080T, 125mV MAX4080S, 50mV MAX4081F/T/S, 0V VREF1B = VREF1A = 2.5V Note 8: Output voltage is internally clamped not to exceed 18V. Note 9: Output settles to within 1% of final value. Note 10: The device will not experience phase reversal when overdriven.
4
_______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Typical Operating Characteristics
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = , TA = +25C, unless otherwise noted.) INPUT OFFSET VOLTAGE INPUT OFFSET VOLTAGE HISTOGRAM vs. TEMPERATURE GAIN ACCURACY vs. TEMPERATURE
MAX4080 toc01 MAX4080 toc02
MAX4080/MAX4081
30 PERCENTAGE (%) 25 20 15 10 5 0 -125 -100 -75 -50 -25 0 25 50 75 100 125 INPUT OFFSET VOLTAGE (V)
INPUT OFFSET VOLTAGE (V)
GAIN ACCURACY (%)
250 200 150 100 50 0 -50 -100 -150 -200 -250 -300 -50 -25
0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
0
75 100 125 150 TEMPERATURE (C)
25
50
-50
-25
0
25
50
75
100
125
TEMPERATURE (C)
GAIN ACCURACY vs. VCC
MAX4080 toc04
MAX4081F/T/S COMMON-MODE REJECTION RATIO vs. FREQUENCY
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 1 10 100 1k 10k 100k FREQUENCY (Hz) 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 -130 1 COMMON-MODE REJECTION RATIO (dB)
MAX4080 toc05
MAX4081F/T/S POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
POWER-SUPPLY REJECTION RATIO (dB)
MAX4080 toc06
0 VRS+ = 48V S VERSION GAIN ACCURACY (%) -0.05
-0.10
T VERSION
-0.15 F VERSION -0.20 4 16 28 40 VCC (V) 52 64 76
1M
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
MAX4081F/T/S REFERENCE REJECTION RATIO vs. FREQUENCY
MAX4080 toc07
MAX4080F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY
MAX4080 toc08
MAX4081F/T/S SMALL-SIGNAL GAIN vs. FREQUENCY
45 40 35 GAIN (dB) 30 25 20 15 10 5 0 MAX4081F VOUT = 100mVP-P MAX4081S
MAX4080 toc09
0 -10 REFERENCE REJECTION RATIO (dB) -20 -30 -40 -50 -60 -70 -80 -90 -100 -110 -120 1 10 100 1k 10k
50 45 40 35 GAIN (dB) 30 25 20 15 10 5 0 MAX4080F VSENSE = 10mV MAX4080S
50
MAX4080T
MAX4081T
100k
0.1
1
10 FREQUENCY (kHz)
100
1000
0.1
1
10 FREQUENCY (kHz)
100
1000
FREQUENCY (Hz)
_______________________________________________________________________________________
MAX4080 toc03
35
300
0.5
5
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
Typical Operating Characteristics (continued)
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = , TA = +25C, unless otherwise noted.)
MAX4080 SUPPLY CURRENT vs. VCC
MAX4080 toc10
MAX4081 SUPPLY CURRENT vs. VCC
120 SUPPLY CURRENT (A) 115 110 105 100 95 90 VREF = 2.5V NO LOAD VSENSE = 0V
MAX4080 toc11
MAX4080 SUPPLY CURRENT vs. TEMPERATURE
110 105 SUPPLY CURRENT (A) 100 95 90 85 80 75 70 65
MAX4080 toc12
85 NO LOAD VSENSE = 0V 80 SUPPLY CURRENT (A)
125
115
75
70
65
60 4 16 28 40 VCC (V) 52 64 76
85 4 16 28 40 VCC (V) 52 64 76
-50
-25
0
25
50
75
100
125
TEMPERATURE (C)
MAX4081 SUPPLY CURRENT vs. TEMPERATURE
MAX4080 toc13
VOUT HIGH VOLTAGE vs. IOUT (SOURCING)
VOUT HIGH VOLTAGE (VCC - VOH) (V) 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 TA = 0C TA = -40C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 IOUT (SOURCING) (mA) TA = +25C VCC = 4.5V TA = +125C TA = +85C
MAX4080 toc14
VOUT LOW VOLTAGE vs. IOUT (SINKING)
VCC = 4.5V 250 VOUT LOW VOLTAGE (mV) 200 150 100 50 TA = 0C 0 0 TA = -40C 50 100 150 200 250 300 350 400 450 500 IOUT (SINKING) (A)
MAX4080 toc15
115 110 105 SUPPLY CURRENT (A) 100 95 90 85 80 75 70 65
VREF1A = VREF1B = 2.5V
0.50
300
TA = +125C TA = +85C TA = +25C
-50
-25
0
25
50
75
100
125
0
TEMPERATURE (C)
MAX4080F SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc16
MAX4080T SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc17
MAX4080S SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc18
INPUT 5mV/div
INPUT 5mV/div
INPUT 5mV/div
OUTPUT 25mV/div
OUTPUT 100mV/div
OUTPUT 300mV/div
20s/div
20s/div
20s/div
6
_______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Typical Operating Characteristics (continued)
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = , TA = +25C, unless otherwise noted.)
MAX4081F SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc19
MAX4080/MAX4081
MAX4081T SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc20
MAX4081S SMALL-SIGNAL TRANSIENT RESPONSE
MAX4080 toc21
INPUT 10mV/div
INPUT 2.5mV/div
INPUT 1mV/div
OUTPUT 50mV/div
OUTPUT 50mV/div
OUTPUT 50mV/div
20s/div
20s/div
20s/div
MAX4080F LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc22
MAX4080T LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc23
MAX4080S LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc24
INPUT 400mV/div
INPUT 100mV/div
INPUT 33mV/div
OUTPUT 2V/div
OUTPUT 2V/div
OUTPUT 2V/div
20s/div
20s/div
20s/div
MAX4081F LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc25
MAX4081T LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc26
MAX4081S LARGE-SIGNAL TRANSIENT RESPONSE
MAX4080 toc27
INPUT 400mV/div
INPUT 100mV/div
INPUT 33mV/div
OUTPUT 2V/div
OUTPUT 2V/div
OUTPUT 2V/div
20s/div
20s/div
20s/div
_______________________________________________________________________________________
7
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
Typical Operating Characteristics (continued)
(VCC = VRS+ = 48V, VSENSE = 0V, CLOAD = 20pF, RLOAD = , TA = +25C, unless otherwise noted.)
MAX4080F SATURATION RECOVERY RESPONSE (VCC = 4.5V)
VCC 5V/div
VCC-TRANSIENT RESPONSE
VCC = 40V
MAX4080 toc28
MAX4080 toc29
MAX4080T STARTUP DELAY (VSENSE = 250mV)
MAX4080 toc30
VRS+ = 20V VCC = 20V STEP VREF1 = VREF2 = 2.5V
INPUT 500mV/div
VCC = 20V
VCC (0 TO 10V) 5V/div
VOUT 1V/div
OUTPUT 2V/div
OUTPUT 2.5V/div
4s/div
20s/div
100s/div
8
_______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Pin Description
PIN MAX4080 1 2 3, 6, 7 4 5 8 -- MAX4081 1 2 3 4 5 8 6 NAME RS+ VCC N.C. GND OUT RSREF1B FUNCTION Power connection to the external-sense resistor. Supply Voltage Input. Decouple VCC to GND with at least a 0.1F capacitor to bypass line transients. No Connection. No internal connection. Leave open or connect to ground. Ground Voltage Output. For the unidirectional MAX4080, VOUT is proportional to VSENSE. For the bidirectional MAX4081, the difference voltage (VOUT - VREF) is proportional to VSENSE and indicates the correct polarity. Load connection to the external sense resistor. Reference Voltage Input: Connect REF1B to REF1A or to GND (see the External Reference section). Reference Voltage Input: Connect REF1A and REF1B to a fixed reference voltage (VREF). VOUT is equal to VREF when VSENSE is zero (see the External Reference section).
MAX4080/MAX4081
--
7
REF1A
Detailed Description
The MAX4080/MAX4081 unidirectional and bidirectional high-side, current-sense amplifiers feature a 4.5V to 76V input common-mode range that is independent of supply voltage. This feature allows the monitoring of current out of a battery as low as 4.5V and also enables high-side current sensing at voltages greater than the supply voltage (VCC). The MAX4080/MAX4081 monitors current through a current-sense resistor and amplifies the voltage across the resistor. The MAX4080 senses current unidirectionally, while the MAX4081 senses current bidirectionally. The 76V input voltage range of the MAX4080/MAX4081 applies independently to both supply voltage (VCC) and common-mode, input-sense voltage (VRS+). Highside current monitoring does not interfere with the ground path of the load being measured, making the MAX4080/MAX4081 particularly useful in a wide range of high-voltage systems. Battery-powered systems require a precise bidirectional current-sense amplifier to accurately monitor the battery's charge and discharge. The MAX4081 charging current is represented by an output voltage from VREF to VCC, while discharge current is given from VREF to GND. Measurements of OUT with respect to VREF yield a positive and negative voltage during charge and discharge, as illustrated in Figure 1 for the MAX4081T.
Current Monitoring
The MAX4080 operates as follows: current from the source flows through RSENSE to the load (Figure 2), creating a sense voltage, VSENSE. Since the internal-sense amplifier's inverting input has high impedance, negligible current flows through RG2 (neglecting the input bias current). Therefore, the sense amplifier's inverting input voltage equals VSOURCE - (ILOAD)(RSENSE). The amplifier's open-loop gain forces its noninverting input to the same voltage as the inverting input. Therefore, the drop across RG1 equals VSENSE. The internal current mirror multiplies IRG1 by a current gain factor, , to give IA2 = IRG1. Amplifier A2 is used to convert the output current to a voltage and then sent through amplifier A3. Total gain = 5V/V for MAX4080F, 20V/V for the MAX4080T, and 60V/V for the MAX4080S. The MAX4081 input stage differs slightly from the MAX4080 (Figure 3). Its topology allows for monitoring of bidirectional currents through the sense resistor. When current flows from RS+ to RS-, the MAX4081 matches the voltage drop across the external sense resistor, RSENSE, by increasing the current through the Q1 and RG1. In this way, the voltages at the input terminals of the internal amplifier A1 are kept constant and an accurate measurement of the sense voltage is achieved. In the following amplifier stages of the MAX4081, the output signal of amplifier A2 is levelshifted to the reference voltage (V REF = V REF1A = VREF1B), resulting in a voltage at the output pin (OUT)
9
_______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
10V SYSTEM LOAD AND CHARGER 5V RS+ 4.5V TO 76V BATTERY ILOAD VSENSE RSENSE RSVCC ICHARGE CHARGE CURRENT
VOUT - VREF
VOUT = 10V VSENSE
MAX4081T
REF1A 5V REF1B OUT
-250mV VOUT = GND -5V
250mV
VREF1A = VREF1B = 5V DISCHARGE CURRENT
GND
Figure 1. MAX4081T OUT Transfer Curve
VSENSE
VSENSE ILOAD RSENSE RS+ RG1 RSRG2
A1 RF RS+ RG1 RSRG2
MAX4081
MAX4080
A1
Q1 Q2 A2 OUT
Q1
CURRENT MIRROR CURRENT MIRROR 125k REF1B 125k REF1A VREF
CURRENT MIRROR
IA2 A2 A3
OUT
GND
Figure 2. MAX4080 Functional Diagram
Figure 3. MAX4081 Functional Diagram
that swings above VREF voltage for positive-sense voltages and below V REF for negative-sense voltages. VOUT is equal to VREF when VSENSE is equal to zero. Set the full-scale output range by selecting RSENSE and the appropriate gain version of the MAX4080/ MAX4081.
10
Note: For Gain = 5 (F), RG1 = RG2 = 160k. For Gain = 20 (T), RG1 = RG2 = 60k. For Gain = 60 (S), RG1 = RG2 = 20k.
______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Table 1. Typical Component Values
FULL-SCALE LOAD CURRENT, ILOAD (A) 0.500 0.125 0.050 5.000 1.250 0.500 50.000 12.500 5.000 CURRENT-SENSE RESISTOR (m) 1000 1000 1000 100 100 100 10 10 10 GAIN (V/V) 5 20 60 5 20 60 5 20 60 FULL-SCALE VSENSE (mV) 500 125 50 500 125 50 500 125 50 MAX4081 FULL-SCALE OUTPUT VOLTAGE (VOUT - VREF, V) 2.5 2.5 3.0 2.5 2.5 3.0 2.5 2.5 3.0
MAX4080/MAX4081
FULL-SCALE LOAD CURRENT, ILOAD (A) 1.000 0.250 0.100 10.000 2.500 1.000 50.000 25.000 10.000
CURRENT-SENSE RESISTOR (m) 1000 1000 1000 100 100 100 10 10 10
GAIN (V/V) 5 20 60 5 20 60 5 20 60
FULL-SCALE VSENSE (mV) 1000 250 100 1000 250 100 500 250 100
MAX4080 FULL-SCALE OUTPUT VOLTAGE (V) 5.0 5.0 6.0 5.0 5.0 6.0 2.5 5.0 6.0
External References (MAX4081)
For the bidirectional MAX4081, the VOUT reference level is controlled by REF1A and REF1B. VREF is defined as the average voltage of VREF1A and VREF1B. Connect REF1A and REF1B to a low-noise, regulated voltage source to set the output reference level. In this mode, VOUT equals VREF1A when VSENSE equals zero (see Figure 4). Alternatively, connect REF1B to ground, and REF1A to a low-noise, regulated voltage source. In this case, the output reference level (VREF) is equal to VREF1A divided by two. VOUT equals VREF1A/2 when VSENSE equals zero. In either mode, the output swings above the reference voltage for positive current-sensing (VRS+ > VRS-). The output swings below the reference voltage for negative current-sensing (VRS+ < VRS-).
Applications Information
Recommended Component Values
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 AV where VSENSE is the full-scale sense voltage, 1000mV for gain of 5V/V, 250mV for gain of 20V/V, 100mV for gain of 60V/V, and AV is the gain of the device. In applications monitoring a high current, ensure that RSENSE is able to dissipate its own I2R loss. If the resistor's power dissipation is exceeded, its value may drift or it may fail altogether. The MAX4080/MAX4081 sense a wide variety of currents with different sense-resistor values. Table 1 lists common resistor values for typical operation.
______________________________________________________________________________________
11
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
ILOAD = 0 RSENSE LOAD RS+ VCC REF1A RSRS+ VCC REF1A 10V 5V REF1B GND OUT 5V GND RSILOAD = 0 RSENSE LOAD
MAX4081
MAX4081
REF1B OUT 5V
Figure 4. MAX4081 Reference Inputs
The full-scale output voltage is VOUT = RSENSE ILOAD (MAX) A V , for the MAX4080 and V OUT = V REF R SENSE I LOAD(MAX) A V for the MAX4081. V SENSE(MAX) is 1000mV for the 5V/V gain version, 250mV for the 20V/V gain version, and 100mV for the 60V/V gain version.
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) PC board layout techniques.
Dynamic Range Consideration
Although the MAX4081 have fully symmetrical bidirectional VSENSE input capability, the output voltage range is usually higher from REF to VCC and lower from REF to GND (unless the supply voltage is at the lowest end of the operating range). Therefore, the user must consider the dynamic range of current monitored in both directions and choose the supply voltage and the reference voltage (REF) to make sure the output swing above and below REF is adequate to handle the swings without clipping or running out of headroom.
Choosing the Sense Resistor
Choose RSENSE based on the following criteria: * Voltage Loss: A high R SENSE value causes the power-source voltage to degrade through IR loss. For minimal voltage loss, use the lowest RSENSE value. * Accuracy: A high RSENSE value allows lower currents to be measured more accurately. This is due to offsets becoming less significant when the sense voltage is larger. For best performance, select RSENSE to provide approximately 1000mV (gain of 5V/V), 250mV (gain of 20V/V), or 100mV (gain of 60V/V) of sense voltage for the full-scale current in each application. * 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. * Inductance: Keep inductance low if ISENSE has a large high-frequency component. Wire-wound resistors have the highest inductance, while metal film is somewhat better. Low-inductance, metal-film resistors are also available. Instead of being spiralwrapped around a core, as in metal-film or wirewound resistors, they are a straight band of metal and are available in values under 1.
12
Power-Supply Bypassing and Grounding
For most applications, bypass VCC to GND with a 0.1F ceramic capacitor. In many applications, VCC can be connected to one of the current monitor terminals (RS+ or RS-). Because VCC is independent of the monitored voltage, VCC can be connected to a separate regulated supply. If VCC will be subject to fast-line transients, a series resistor can be added to the power-supply line of the MAX4080/MAX4081 to minimize output disturbance. This resistance and the decoupling capacitor reduce the rise time of the transient. For most applications, 1k in conjunction with a 0.1F bypass capacitor work well. The MAX4080/MAX4081 require no special considerations with respect to layout or grounding. Consideration should be given to minimizing errors due to the large charge and discharge currents in the system.
______________________________________________________________________________________
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Power Management
The bidirectional capability of the MAX4081 makes it an excellent candidate for use in smart battery packs. In the application diagram (Figure 5), the MAX4081 monitors the charging current into the battery as well as the discharge current out of the battery. The microcontroller stores this information, allowing the system to query the battery's status as needed to make system power-management decisions.
SYSTEM POWER MANAGEMENT AND CHARGER CIRCUITRY RSENSE
MAX4080/MAX4081
RS+ VCC
RS-
MAX4081 REF1A
GND REF1B 1.8V BATTERY
OUT
PART MAX4080FAUA MAX4080FASA MAX4080TAUA MAX4080TASA MAX4080SAUA MAX4080SASA MAX4081FAUA MAX4081FASA MAX4081TAUA MAX4081TASA MAX4081SAUA MAX4081SASA
GAIN (V/V) 5 5 20 20 60 60 5 5 20 20 60 60
ISENSE Unidirectional Unidirectional Unidirectional Unidirectional Unidirectional Unidirectional Bidirectional Bidirectional Bidirectional Bidirectional Bidirectional Bidirectional
VCC = 4.5V TO 76V
Figure 5. MAX4081 Used In Smart-Battery Application
Typical Operating Circuit
ISENSE RSENSE RS+ VCC RSSYSTEM LOAD
MAX4080
OUT
Chip Information
TRANSISTOR COUNT: 185 PROCESS: Bipolar
______________________________________________________________________________________
MAX1243 ADC
C
Selector Guide
SERIAL INTERFACE
GND
13
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 8 MAX 8 SO PACKAGE CODE U8-2 S8-2 DOCUMENT NO. 21-0036 21-0041
14
______________________________________________________________________________________
8LUMAXD.EPS
76V, High-Side, Current-Sense Amplifiers with Voltage Output
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX4080/MAX4081
INCHES DIM A A1 B C e E H L MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050
MILLIMETERS MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 1.27
N
E
H
VARIATIONS:
1
INCHES
MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC
TOP VIEW
DIM D D D
MIN 0.189 0.337 0.386
MAX 0.197 0.344 0.394
D A e B A1 L C
0-8
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0041
B
1 1
______________________________________________________________________________________
SOICN .EPS
15
76V, High-Side, Current-Sense Amplifiers with Voltage Output MAX4080/MAX4081
Revision History
REVISION NUMBER 0 1 REVISION DATE 10/02 11/08 Initial release Added values for RG1 and RG2 DESCRIPTION PAGES CHANGED -- 10
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.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

▲Up To Search▲

Price & Availability of MAX408008

	To Download MAX408008 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .