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LMP8481MMX-H/NOPB

LMP8481MMX-H/NOPB

  • 厂商:

    BURR-BROWN(德州仪器)

  • 封装:

    VSSOP8

  • 描述:

    ICOPAMPCURRSENS270KHZ8VSSOP

  • 数据手册
  • 价格&库存
LMP8481MMX-H/NOPB 数据手册
Product Folder Order Now Technical Documents Support & Community Tools & Software LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 LMP848x Precision 76-V High-Side Current Sense Amplifiers With Voltage Output 1 Features 3 Description • • • • • • • • • • • • • • The LMP8480 and LMP8481 are precision high-side current sense amplifiers that amplify a small differential voltage developed across a current sense resistor in the presence of high input common-mode voltages. These amplifiers are designed for bidirectional (LMP8481) or unidirectional (LMP8480) current applications and accept input signals with common-mode voltage range from 4 V to 76 V with a bandwidth of 270 kHz. Because the operating power supply range overlaps the input common-mode voltage range, the LMP848x can be powered by the same voltage that is being monitored. This benefit eliminates the need for an intermediate supply voltage to be routed to the point of load where the current is being monitored, resulting in reduced component count and board space. 1 Typical Values: TA = 25°C Bidirectional or Unidirectional Sensing Common Mode Voltage Range: 4.0 V to 76 V Supply Voltage Range: 4.5 V to 76 V Fixed Gains: 20, 60, and 100 V/V Gain Accuracy: ±0.1% Offset: ±80 µV Bandwidth (–3 dB): 270 kHz Quiescent Current: < 100 µA Buffered High-Current Output: > 5 mA Input Bias Current: 7 µA PSRR (DC): 122 dB CMRR (DC): 124 dB Temperature Range: –40°C to 125°C 2 Applications • • • • • • • High-Side Current Sense Vehicle Current Measurement Telecommunications Motor Controls Laser or LED Drivers Energy Management Solar Panel Monitoring The LMP848x family consists of fixed gains of 20, 60, and 100 for applications that demand high accuracy over temperature. The low-input offset voltage allows the use of smaller sense resistors without sacrificing system error. The wide operating temperature range of –40°C to 125°C makes the LMP848x an ideal choice for automotive, telecommunications, industrial, and consumer applications. The LMP8480 and LMP8481 are pin-for-pin replacements for the MAX4080 and MAX4081, offering improved offset voltage, wider reference adjust range and higher output drive capabilities. The LMP8480 and LMP8481 are available in a 8-pin VSSOP package. Device Information(1) PART NUMBER Typical Application Schematic PACKAGE BODY SIZE (NOM) LMP8480 VSSOP (8) 3.00 mm x 3.00 mm LMP8481 VSSOP (8) 3.00 mm x 3.00 mm (1) For all available packages, see the orderable addendum at the end of the datasheet. RSP RSN Copyright © 2016, Texas Instruments Incorporated 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Table of Contents 1 2 3 4 5 6 7 8 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Device Comparison Table..................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 3 4 7.1 7.2 7.3 7.4 7.5 7.6 4 4 4 4 5 7 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description ............................................ 10 8.1 8.2 8.3 8.4 Overview ................................................................. Functional Block Diagrams ..................................... Feature Description................................................. Device Functional Modes........................................ 10 11 12 17 9 Application and Implementation ........................ 18 9.1 Application Information............................................ 18 9.2 Typical Applications ................................................ 18 10 Power Supply Recommendations ..................... 21 10.1 Power Supply Decoupling ..................................... 21 11 Layout................................................................... 21 11.1 Layout Guidelines ................................................. 21 11.2 Layout Example .................................................... 21 12 Device and Documentation Support ................. 22 12.1 12.2 12.3 12.4 12.5 12.6 12.7 Device Support .................................................... Related Links ........................................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 22 22 22 22 22 22 22 13 Mechanical, Packaging, and Orderable Information ........................................................... 23 4 Revision History Changes from Revision D (April 2016) to Revision E Page • Deleted last Features bullet ................................................................................................................................................... 1 • Deleted LMP8480-H row from Device Comparison Table ..................................................................................................... 3 • Changed REFA to REFB and REFB to REFA for pins 6 and 7, respectively, in Pin Functions table ................................... 3 • Deleted NCQ column from Thermal Information table ........................................................................................................... 4 • Changed bidirectional to unidirectional is description of Figure 22 in Basic Connections section ...................................... 13 Changes from Revision C (September 2015) to Revision D Page • Changed Typical Application Schematic: swapped RSN and RSP labels ............................................................................. 1 • Changed conditions of Electrical Characteristics table ......................................................................................................... 5 • Added unit to ROUT parameter in Electrical Characteristics table .......................................................................................... 5 • Changed first paragraph of Overview section ..................................................................................................................... 10 Changes from Revision B (December 2014) to Revision C Page • Deleted WSON package option for LMP8480 and LMP8481 ............................................................................................... 1 • Deleted -F version (50x gain) for LMP8480 and LMP8481.................................................................................................... 3 • Deleted WSON package options for LMP8480 and LMP8481 ............................................................................................. 3 Changes from Revision A (August 2012) to Revision B • 2 Page Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 5 Device Comparison Table DEVICE NAME GAIN POLARITY LMP8480-T x20 Unidirectional LMP8480-S x60 Unidirectional LMP8481-T x20 Bidirectional or unidirectional LMP8481-S x60 Bidirectional or unidirectional LMP8481-H x100 Bidirectional or unidirectional 6 Pin Configuration and Functions LMP8480 VSSOP Package 8 Pins Top View LMP8481 VSSOP Package 8 Pins Top View Pin Functions PIN NO. NAME I/O DESCRIPTION 1 RSP I Positive current sense input 2 VCC P Positive supply voltage 3 NC — No connection – not internally connected 4 GND P Ground 5 VOUT O Output 6 NC or REFB I LMP8480: no connection LMP8481: reference voltage “B” input 7 NC or REFA I LMP8480: no connection LMP8481: reference voltage “A” input 8 RSN I Negative current sense input Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 3 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com 7 Specifications 7.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) (3) Supply voltage (VCC to GND) RSP or RSN to GND VOUT to GND MIN MAX UNIT –0.3 85 V –0.3 85 V –0.3 to the lesser of (VCC + 0.3) or +20 VREF pins (LMP8481 only) Other VREF pin tied to ground –0.3 12 Applied to both VREF pins tied together –0.3 6 Differential input voltage V V –85 85 V Current into output pin –20 (4) 20 mA Current into any other pins –5 (4) 5 mA Operating temperature –40 125 °C Junction temperature -40 150 °C Storage temperature –65 150 °C (1) (2) (3) (4) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJ(MAX), θJA, and the ambient temperature, TA. The maximum allowable power dissipation PDMAX = (TJ(MAX) –TA)/ θJA or the number given in Absolute Maximum Ratings, whichever is lower. If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/Distributors for availability and specifications. 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 under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. When the input voltage (VIN) at any pin exceeds power supplies (VIN < GND or VIN > VS ), the current at that pin must not exceed 5 mA, and the voltage (VIN) has to be within the Absolute Maximum Ratings for that pin. The 20-mA package input current rating limits the number of pins that can safely exceed the power supplies with current flow to four pins. 7.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) ±2000 Charged-device model (CDM), per JEDEC specification JESD22C101 (2) ±750 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 7.3 Recommended Operating Conditions Expected normal operating conditions over free-air temperature range (unless otherwise noted) (1) Supply voltage (VCC) Common mode voltage Reference input (LMP8481 only) (1) MIN MAX 4.5 76 V 4.0 76 V VREFA and VREFB tied together –0.3 to the lesser of (VCC – 1.5) or +6 Single VREF pin with other VREF pin grounded –0.3 or +12 where the average of the two VREF pins is less than the lesser of (VCC – 1.5) or +6 UNIT V Exceeding the Recommended Operating Conditions for extended periods of time may effect device reliability or cause parametric shifts. 7.4 Thermal Information LMP8480, LMP8481 THERMAL METRIC (1) DGK (VSSOP) UNIT 8 PINS RθJA (1) 4 Junction-to-ambient thermal resistance 185 °C/W For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 7.5 Electrical Characteristics unless otherwise specified, all limits specified for at TA = 25°C, VCC = 4.5 V to 76 V, 4.5 V ≤ VCM ≤ 76 V, RL = 100 kΩ, VSENSE = (VRSP – VRSN) = 0 V (1) PARAMETER VOS Input offset voltage (RTI) TCVOS Input offset voltage drift (4) TEST CONDITIONS VCC = VRSP = 48 V, ΔV = 100 mV MIN (2) TA = 25°C TYP (3) MAX (2) ±80 ±265 –40°C ≤ TA ≤ 125°C ±900 ±6 Input bias current (5) VCC = VRSP = 76 V, per input IB Input leakage current VSENSE (MAX) 2 -T version, –40°C ≤ TA ≤ 125°C 667 -F version, –40°C ≤ TA ≤ 125°C 267 -S version, –40°C ≤ TA ≤ 125°C 222 -H version, –40°C ≤ TA ≤ 125°C 133 20 -T version, –40°C ≤ TA ≤ 125°C 19.8 -S version Gain 59.5 -H version 99.2 DC power supply rejection ratio ±0.6% –40°C ≤ TA ≤ 125°C VRSP = 48 V, VCC = 4.5 V to 76 V, –40°C ≤ TA ≤ 125°C ±0.8% 122 VCC = 48 V, VRSP = 4.5 V to 76 V, –40°C ≤ TA ≤ 125°C dB 100 VCC = 48 V, VRSP = 4.5 V to 76 V DC CMRR DC common mode rejection ratio 124 100 VCC = 48 V, VRSP = 4 V to 76 V dB 124 CMVR Input common mode voltage range CMRR > 100 dB, –40°C ≤ TA ≤ 125°C ROUT Output resistance / load regulation VSENSE = 100 mV 0.1 VOMAX Maximum output voltage (headroom) (VOMAX = VCC – VOUT) VCC = 4.5 V, VRSP = 48 V, VSENSE = +1 V, IOUT (sourcing) 500 μA 230 (1) (2) (3) (4) (5) (6) V/V 100.8 TA = 25°C VRSP = 48 V, VCC = 4.5 V to 76 V DC PSRR 60.5 100 -H version, –40°C ≤ TA ≤ 125°C VCC = VRSP = 48 V 20.2 60 -S version, –40°C ≤ TA ≤ 125°C Gain error μA mV -T version AV μA 0.01 VCC = 0, VRSP = 86 V, both inputs together, –40°C ≤ TA ≤ 125°C VCC = 16 µV°C 12 VCC = 0, VRSP = 86 V, both inputs together Differential input voltage across sense resistor (6) µV 6.3 VCC = VRSP = 76 V, per input, –40°C ≤ TA ≤ 125°C ILEAK UNIT 4 76 V Ω 500 mV Electrical Characteristics table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA. All limits are specified by testing, design, or statistical analysis. Typical values represent the most likely parametric norm at the time of characterization. Actual typical values can vary over time and also depend on the application and configuration. The typical values are not tested and are not ensured on shipped production material. Offset voltage temperature drift is determined by dividing the change in VOS at the temperature extremes by the total temperature change. Positive bias current corresponds to current flowing into the device. This parameter is specified by design and/or characterization and is not tested in production. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 5 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Electrical Characteristics (continued) unless otherwise specified, all limits specified for at TA = 25°C, VCC = 4.5 V to 76 V, 4.5 V ≤ VCM ≤ 76 V, RL = 100 kΩ, VSENSE = (VRSP – VRSN) = 0 V(1) PARAMETER MIN (2) TEST CONDITIONS VCC = VRSP = 48 V, VSENSE = –1 V, IOUT (sinking) = 10 µA TYP (3) Minimum output voltage UNIT 3 VCC = VRSP = 48 V, VSENSE = –1 V, IOUT (sinking) = 10 µA, –40°C ≤ TA ≤ 125°C VOMIN MAX (2) 15 VCC = VRSP = 4.5 V, VSENSE = –1 V, IOUT (sinking) = 10 µA 3 VCC = VRSP = 48 V, VSENSE = –1 V, IOUT (sinking) = 100 µA 18 mV VCC = VRSP = 48 V, VSENSE = –1 V, IOUT (sinking) = 100 µA, –40°C ≤ TA ≤ 125°C 55 VCC = VRSP = 4.5 V, VSENSE = –1 V, IOUT (sinking) = 100 µA 18 12 VOLOAD Output voltage with load VCC = 28 V, VRSP = 28 V, VSENSE = 600 mV, I OUT (sourcing) = 500 µA VOLREG Output load regulation VCC = 20, VRSP = 16 V, VOUT = 12, ΔIL = 200 nA to 8 mA ICC Supply current VOUT = 2 V, RL = 10 MΩ, VCC = VRSP = 76 V, –40°C ≤ TA ≤ 125°C BW –3-dB bandwidth RL = 10 MΩ, CL = 20 pF SR Slew rate (7) VSENSE from 10 mV to 80 mV, RL = 10 MΩ, CL = 20 pF eni Input referred voltage noise tSETTLE Output settling time to 1% of final value tPU V 0.001% VOUT = 2 V, RL = 10 MΩ, VCC = VRSP = 76 V 88 155 µA 270 kHz 1 V/µs f = 1 kHz 95 nV/√Hz VSENSE = 10 mV to 100 mV and 100 mV to 10 mV 20 µs Power-up time VCC = VRSP = 48 V, VSENSE = 100 mV, output to 1% of final value 50 µs tRECOVERY Saturation recovery time Output settles to 1% of final value, the device does not experience phase reversal when overdriven 50 µs CLOAD Max output capacitance load No sustained oscillations 500 pF (7) 6 The number specified is the average of rising and falling slew rates and measured at 90% to 10%. Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 7.6 Typical Characteristics unless otherwise specified, TA = 25°C, VCC = 4.5 V to 76 V, 4.5 V < VCM < 76 V, RL = 100 kΩ, VSENSE = (VRSP – VRSN) = 0 V, for all gain options Figure 1. Offset Voltage Histogram Figure 2. Typical Offset Voltage vs Temperature Figure 3. Typical Gain Accuracy vs Temperature Figure 4. Typical Gain Accuracy vs Supply Voltage Figure 5. Typical Offset Voltage vs Supply Voltage Figure 6. AC Common-Mode Rejection Ratio vs Frequency Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 7 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Typical Characteristics (continued) unless otherwise specified, TA = 25°C, VCC = 4.5 V to 76 V, 4.5 V < VCM < 76 V, RL = 100 kΩ, VSENSE = (VRSP – VRSN) = 0 V, for all gain options 8 Figure 7. AC Power Supply Rejection Ratio vs Frequency Figure 8. Small Signal Gain vs Frequency Figure 9. Large Signal Pulse Response Figure 10. Small Signal Pulse Response Figure 11. Supply Current vs Supply Voltage Figure 12. Supply Current vs Temperature Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 Typical Characteristics (continued) unless otherwise specified, TA = 25°C, VCC = 4.5 V to 76 V, 4.5 V < VCM < 76 V, RL = 100 kΩ, VSENSE = (VRSP – VRSN) = 0 V, for all gain options Figure 13. Saturated Output Sourcing Current at 4.5 V Figure 14. Saturated Output Sinking Current at 4.5 V Figure 15. Saturated Output Sourcing Current at 12 V Figure 16. Saturated Output Current Sinking at 12 V Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 9 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com 8 Detailed Description 8.1 Overview The LMP8480 and LMP8481 are single-supply, high-side current sense amplifiers with available fixed gains of x20, x60 and x100. The power supply range is 4.5 V to 76 V, and the common-mode input voltage range is capable of 4.0-V to 76-V operation. The supply voltage and common-mode range are completely independent of each other, which causes the LMP848x supply voltage to be extremely flexible because the LMP848x supply voltage can be greater than, equal to, or less than the load source voltage, and allows the device to be powered from the system supply or the load supply voltage. The LMP8480 and LMP8481 supply voltage does not have to be larger than the load source voltage. A 76-V load source voltage with a 5-V supply voltage is perfectly acceptable. 8.1.1 Theory of Operation The LMP8480 and LMP8481 are comprised of two main stages. The first stage is a differential input current to voltage converter, followed by a differential voltage amplifier and level-shifting output stage. Also present is an internal 14-V low-dropout regulator (LDO) to power the amplifiers and output stage, as well as a reference divider resistor string to allow the setting of the reference level. As Figure 18 illustrates, the current flowing through RSENSE develops a voltage drop called VSENSE. The voltage across the sense resistor, VSENSE, is then applied to the input RSP and RSN pins of the amplifier. Internally, the voltage on each input pin is converted to a current by the internal precision thin-film input resistors RGP and RGN. A second set of much higher value VCM sense resistors between the inputs provide a sample of the input common-mode voltage for internal use by the differential amplifier. VSENSE is applied to the differential amplifier through RGP and RGN. These resistors change the input voltage to a differential current. The differential amplifier then servos the resistor currents through the MOSFETs to maintain a zero balance across the differential amplifier inputs. With no input signal present, the currents in RGP and RGN are equal. When a signal is applied to VSENSE, the current through RGP and RGN are imbalanced and are no longer equal. The amplifier then servos the MOSFETS to correct this current imbalance, and the extra current required to balance the input currents is then reflected down into the two lower 400-kΩ tail resistors. The difference in the currents into the tail resistors is therefore proportional to the amplitude and polarity of VSENSE. The tail resistors, being larger than the input resistors for the same current, then provide voltage gain by changing the current into a proportionally larger voltage. The gain of the first stage is then set by the tail resistor value divided by RG value. The differential amplifier stage then samples the voltage difference across the two 400-kΩ tail resistors and also applies a further gain-of-five and output level-shifting according to the applied reference voltage (VREF). The resulting output of the amplifier will be equal to the differential input voltage times the gain of the device, plus any voltage value applied to the two VREF pins. The resistor values in the schematic are ideal values for clarity and understanding. Table 1 shows the actual values used that account for parallel combinations and loading. This table can be used for calculating the effects of any additional external resistance. The LMP8480 is identical to the LMP8481, except that both the VREF pins are grounded internally. Table 1. Actual Internal Resistor Values GAIN OPTION 10 RGP AND RGN (Each) RVCMSENSE (Each) RTAIL (Each) DIFFERENTIAL AMP FB (Each) VREFx RESISTORS (Each) 20x 98.38 k 491.9 k 393.52 k 1967.6 k 98.38 k 60x 32.793 k 172.165 k 393.52 k 1967.6 k 98.38 k 100x 19.676 k 98.38 k 393.52 k 1967.6 k 98.38 k Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 8.2 Functional Block Diagrams RSN RSP LMP8480 VSENSE VCM SENSE RGP VCC Difference Amplifier (x5) Internal 14V LDO Regulator + RGN 2 M: - + VOUT 100 k: V to I Converter 1.95 M: 100 k: 400 k: 400 k: Copyright © 2016, Texas Instruments Incorporated GND Figure 17. LMP8480 Block Diagram RSN RSP LMP8481 VSENSE RGP VCC Internal 14V LDO Regulator VCM SENSE + Difference Amplifier (x5) RGN 2 M: - + VOUT 100 k: V to I Converter VREFA 1.95 M: 100 k: 400 k: 400 k: GND VREFB Copyright © 2016, Texas Instruments Incorporated Figure 18. LMP8481 Block Diagram Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 11 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com 8.3 Feature Description 8.3.1 Basic Connections Figure 19 through Figure 22 show the basic connections for several different configurations. Figure 19 shows the basic connections for the LMP8480 for unidirectional applications. The output is at zero with zero sense voltage. +4.0V to +76V ISENSE VCC = +4.5V to +76V To Load RSENSE CBYPASS 0.1PF VCC RSN VSENSE OUTPUT LMP8480 VOUT RSP GND Figure 19. LMP8480 Basic Connections (Unidirectional) Figure 20 shows the basic connections for the LMP8481 for bidirectional applications using an external reference input. At zero input voltage, the output is at the applied reference voltage (VREF), moving positive or negative from the zero reference point. +4.0V to +76V ISENSE VCC = +4.5V to +76V To Load RSENSE CBYPASS 0.1PF VCC RSN VSENSE OUTPUT LMP8481 VOUT REFA RSP REFB GND VREF INPUT Figure 20. LMP8481 Basic Connections for External 1:1 VREF Input (Bidirectional) Figure 21 shows the basic connections for the LMP8481 for bidirectional applications centering the output at onehalf the applied VREF or VCC voltage. If VREFA is connected to VCC, then the output zero point is VCC / 2. If VREFA is connected to the ADC VREF line, then the zero output is at mid-scale for the ADC. +4.0V to +76V ISENSE VCC = +4.5V to +76V To Load RSENSE CBYPASS 0.1PF VCC RSN VSENSE OUTPUT LMP8481 VOUT REFA RSP REFB GND VREF or VCC Figure 21. LMP8481 Basic Connections for Mid-Bias (VREF / 2) Input (Bidirectional) 12 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 Feature Description (continued) Figure 22 shows the how to connect the LMP8481 for unidirectional applications, thus making the LMP8481 equivalent to the LMP8480 in Figure 19. ISENSE +4.0V to +76V VCC = +4.5V to +76V To Load RSENSE CBYPASS 0.1PF VCC RSN VSENSE LMP8481 VOUT OUTPUT REFA RSP REFB GND Figure 22. LMP8481 Connections for Unidirectional Configuration (Equivalent to LMP8480 Unidirectional) 8.3.2 Selection of the Sense Resistor The accuracy of the current measurement depends heavily on the accuracy of the shunt resistor RSENSE. The value of RSHUNT depends on the application and is a compromise between small-signal accuracy, maximum permissible voltage drop, and allowable power dissipation in the current measurement circuit. The use of a 4-terminal or Kelvin sense resistor is highly recommended; see the Layout Guidelines section. For best results, the value of the resistor is calculated from the maximum expected load current ILMAX and the expected maximum output swing VOUTMAX, plus a few percent of headroom. See the Maximum Output Voltage section for details about the maximum output voltage limits. High values of RSENSE provide better accuracy at lower currents by minimizing the effects of amplifier offset. Low values of RSENSE minimize load voltage loss, but at the expense of accuracy at low currents. A compromise between low current accuracy and load circuit losses must generally be made. The maximum VSENSE voltage that must be generated across the RSENSE resistor is shown in Equation 1: VSENSE = VOUTMAX / AV (1) NOTE The maximum VSENSE voltage must be no more than 667 mV. From this maximum VSENSE voltage, the RSENSE value can be calculated from Equation 2: RSENSE = VSENSE / ILMAX (2) Take care not exceed the maximum power dissipation of the resistor. The maximum sense resistor power dissipation is shown in Equation 3: PRSENSE = VSENSE × ILMAX (3) Using a 2-3x minimum safety margin is recommended in selecting the power rating of the resistor. 8.3.3 Using PCB Traces as Sense Resistors While it may be tempting to use a known length of PCB trace resistance as a sense resistor, it is not recommended. The temperature coefficient of copper is typically 3300-4000 ppm/°K, and can vary over PCB process variations and require measurement correction (possibly requiring ambient temperature measurements). A typical surface mount sense resistor tempco is in the 50 ppm to 500 ppm/°C range offering more measurement consistency and accuracy over the copper trace. Special low-tempco resistors are available in the 0.1 to 50 ppm range, but at a higher cost. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 13 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Feature Description (continued) 8.3.4 VREFA and VREFB Pins (LMP8481 Only) The voltage applied to the VREFA and VREFB pins controls the output zero reference level. Depending on how the pins are configured, the output reference level can be set to GND, or VCC / 2, or external VREF / 2, or the average of two different input references. The reference inputs consist of a pair of divider resistors with equal values to a common summing point, VREF', as shown in Figure 23. Assuming VSENSE is zero, the output is at the same value as VREF'. Figure 23. VREF Input Resistor Network VREF' is the voltage at the resistor tap-point that is directly applied to the output as an offset. With the two VREF inputs tied together, the output zero voltage has a 1:1 ratio relationship with VREF. VOUT = ( (VRSP – VRSN) ×Av ) + VREF’ (4) Where: VREF’ = VREFA = VREFB (Equal Inputs) (5) VREF’ = ( VREFA + VREFB ) / 2 (Different Inputs) (6) or: 8.3.4.1 One-to-One (1:1) Reference Input To directly set the reference level, the two inputs are connected to the external reference voltage. The applied VREF is reflected 1:1 on the output, as shown in Figure 24. Figure 24. Applying 1:1 Direct Reference Voltage 14 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 Feature Description (continued) 8.3.4.2 Setting Output to One-Half VCC or external VREF For mid-range operation, VREFB must be tied to ground and VREFA can be tied to VCC or an external A/D reference voltage. The output is set to one-half the reference voltage. For example, a 5-V reference results in a 2.5-V output zero reference. Figure 25. Applying a Divided Reference Voltage VREF’ = (VREFA – VREFB) / 2 (7) When the reference pins are biased at different voltages, the output is referenced to the average of the two applied voltages. The reference pins must always be driven from clean, stable sources, such as A/D reference lines or clean supply lines. Any noise or drifts on the reference inputs are directly reflected in the output. Take care if the power supply is used as the reference source so as to not introduce supply noise, drift or sags into the measurement. Different resistor divider ratios can be set by adding external resistors in series with the internal 100-kΩ resistors, though the temperature coefficient (tempco) of the external resistors may not tightly track the internal resistors and there are slight errors over temperature. The LMP8480 is identical to the LMP8481, except that both the VREF pins are grounded internally. The LMP8481 can replace the LMP8480 if both VREF pins are grounded. 8.3.5 Reference Input Voltage Limits (LMP8481 Only) The maximum voltage on either reference input pin is limited to VCC or 12 V, whichever is less. The average voltage on the two VREF pins, and thus the actual output reference voltage level, is limited to a maximum of 1.5 V below VCC, or 6 V, whichever is less. Beware that supply voltages of less than 7.5 V have a diminishing VREF maximum. Both VREFA and VREFB can both be grounded to provide a ground referenced output (thus functionally duplicating the LMP8480). Note that there can be a dynamic error in the VREF to output level matching of up to 100 µV/V. Normally this error is not an issue for fixed references, but if the reference voltage is dynamically adjusted during operation, this error must be taken into account during calibration routines. This error varies in both amplitude and polarity partto-part, but the slope is generally linear. 8.3.6 Low-Side Current Sensing The LMP8480 and LMP8481 are not recommended for low-side current sensing at ground level. The voltage on either input pin must be a minimum of 4.0 V above the ground pin for proper operation. The output level may not be valid for common-mode voltages below 4 V. This minimum voltage requirement must be taken into consideration for monitoring or feedback applications where the load-supply voltage can dip below 4 V or be switched completely off. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 15 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Feature Description (continued) 8.3.7 Input Series Resistance Because the input stage uses precision resistors to convert the voltage on the input pin to a current, any resistance added in series with the input pins changes the gain. If a resistance is added in series with an input, the gain of that input does not track that of the other input, causing a constant gain error. TI does not recommend using external resistances to alter the gain because external resistors do not have the same thermal matching as the internal thin film resistors. If resistors are purposely added for filtering, resistance must be added equally to both inputs and the user must be aware that the gain changes slightly. See the end of the Theory of Operation section for the internal resistor values. External resistances must be kept below 10 Ω. 8.3.8 Minimum Output Voltage The amplifier output cannot swing to exactly 0 V. There is always a minimum output voltage set by the output transistor saturation and input offset errors. This voltage creates a minimum output swing around the zero current reading resulting from the output saturation. The user must be aware of this output swing when designing any servo loops or data acquisition systems that may assume 0 V = 0 A. If a true zero is required, use the LMP8481 with a VREF set slightly above ground (> 50 mV); see the Swinging Output Below Ground section for a possible solution to this issue. 8.3.9 Swinging Output Below Ground If a negative supply is available, a pulldown resistor can be added from the output to the negative voltage to allow the output to swing a few millivolts below ground. Adding a pulldown resistor allows the ADC to resolve true zero and recover codes that normally are lost to the negative output saturation limit. Figure 26. Output Pulldown Resistor Example A minimum of 50 µA must be sourced (pulled) from the output to a negative voltage. The pulldown resistor can be calculated from: RPD = –VS / 50 µA (8) For example, if a –5-V supply is available, use a pulldown resistor of 5 V / 50 µA = 100 kΩ. Adding this resistor allows the output to swing to approximately 10 mV below ground. This technique can also reduce the maximum positive swing voltage. Do not forget to include the parallel loading effects of the pulldown any output load. Exceeding –100 mV on the output is not recommended. Source currents greater than 100 µA must be avoided to prevent self-heating at high-supply voltages. Pulldown resistor values must not be so low as to heavily load the output during positive output excursions. This mode of operation is not directly specified and is not ensured. 16 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 Feature Description (continued) 8.3.10 Maximum Output Voltage The LMP8481 has an internal precision 14-V low-dropout regulator that limits the maximum amplifier output swing to approximately 250 mV below VCC or 13.7 V (whichever is less). This regulator effectively clamps the maximum output to slightly less than 13.7 V even with a VCC greater than 14 V; see Typical Application With a Resistive Divider section for more information. 8.4 Device Functional Modes 8.4.1 Unidirectional vs Bidirectional Operation Unidirectional operation is where the load current only flows in one direction (VSENSE is always positive). Application examples are PA monitoring, non-inductive load monitoring, and laser or LED drivers. Unidirectional operation allows the output zero reference to be true zero volts on the output. The LMP8480 is designed for unidirectional applications where the setting of VREF is not required; see the Unidirectional Application With the LMP8480 section for more details. Bidirectional operation is where the load current can flow in both directions (VSENSE can be positive or negative). Application examples are battery-charging or regenerative motor monitoring. The LMP8481 is designed for bidirectional applications and has a pair of VREF pins to allow the setting of the output zero reference level (VREF); see the Unidirectional Application With the LMP8480 section for more details. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 17 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 9.1 Application Information The LMP848x amplifies the voltage developed across a current-sensing resistor when current passes through it. Flexible offset inputs allow adjusting the functionality of the output for multiple configurations, as discussed throughout this section. 9.1.1 Input Common-Mode and Differential Voltage Range The input common-mode range, where common-mode range is defined as the voltage from ground to the voltage on RSP input, must be in the range of 4.0 V to 76 V. Operation below 4.0 V on either input pin introduces severe gain error and nonlinearities. The maximum differential voltage (defined as the voltage difference between RSP and RSN) must be 667 mV or less. The theoretical maximum input is 700 mV (14 V / 20). Taking the inputs below 4 V does not damage the device, but the output conditions during this time are not predictable and are not ensured. If the load voltage (Vcm) is expected to fall below 4 V as part of normal operation, preparations must be made for invalid output levels during this time. 9.2 Typical Applications 9.2.1 Unidirectional Application With the LMP8480 Copyright © 2016, Texas Instruments Incorporated Figure 27. Unidirectional Application with the LMP8480 9.2.1.1 Design Requirements The LMP8480 is designed for unidirectional current sense applications. The output of the amplifier is equal to the differential input voltage times the fixed device gain. 9.2.1.2 Detailed Design Procedure The output voltage can be calculated from Equation 9: VOUT = ( (VRSP – VRSN) × Av ) 18 Submit Documentation Feedback (9) Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 Typical Applications (continued) Note that the minimum zero reading is limited by the lower output swing and input offset. The LMP8480 is functionally identical to the LMP8481, but with the VREFA and VREFB nodes grounded internally. The LMP8481 can replace the LMP8480 if both the VREF inputs (pins 6 and 7) are grounded. 9.2.1.3 Application Curve Figure 28. Unidirectional Transfer Function for Gain-of-20 Option 9.2.2 Bidirectional Current Sensing Using the LMP8481 RSP RSN Copyright © 2016, Texas Instruments Incorporated Figure 29. Bidirectional Current Sensing Using the LMP8481 9.2.2.1 Design Requirements Bidirectional operation is required where the measured load current can be positive or negative. Because VSENSE can be positive or negative, and the output cannot swing negative, the zero output level must be level-shifted above ground to a known zero reference point. The LMP8481 allows for the setting this reference point. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 19 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com Typical Applications (continued) 9.2.2.2 Detailed Design Procedure The VREFA and VREFB pins set the zero reference point. The output zero reference point is set by applying a voltage to the REFA and REFB pins; see the Unidirectional Application With the LMP8480 section. The VREFA and VREFB Pins (LMP8481 Only) section describes the output transfer function with a 1.2-V reference applied to the gain-of-20 option. 9.2.2.3 Application Curve Figure 30. Bidirectional Transfer Function Using a 1.2-V Reference Voltage 9.2.3 Typical Application With a Resistive Divider Take care if the output is driving an A/D input with a maximum A/D maximum input voltage lower than the amplifier supply voltage because the output can swing higher than the planned load maximum resulting from input transients or shorts on the load and overload or possibly damage the A/D input. A resistive attenuator, as shown in Figure 31, can be used to match the maximum swing to the input range of the A/D converter. Copyright © 2016, Texas Instruments Incorporated Figure 31. Typical Application With Resistive Divider Example 20 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 10 Power Supply Recommendations 10.1 Power Supply Decoupling In order to decouple the LMP848x from ac noise on the power supply, TI recommends using a 0.1-μF bypass capacitor between the VCC and GND pins. This capacitor must be placed as close as possible to the supply pins. In some cases, an additional 10-μF bypass capacitor can further reduce the supply noise. Do not forget that these bypass capacitors must be rated for the full supply and load source voltage. TI recommends that the working voltage of the capacitor (WVDC) be at least two times the maximum expected circuit voltage. 11 Layout 11.1 Layout Guidelines The traces leading to and from the sense resistor can be significant error sources. With small value sense resistors (< 100 mΩ), any trace resistance shared with the load current can cause significant errors. The amplifier inputs must be directly connected to the sense resistor pads using Kelvin or 4-wire connection techniques. The traces must be one continuous piece of copper from the sense resistor pad to the amplifier input pin pad, and ideally on the same copper layer with minimal vias or connectors. These recommendations can be important around the sense resistor if any significant heat gradients are being generated. To minimize noise pickup and thermal errors, the input traces must be treated as a differential signal pair and routed tightly together with a direct path to the input pins. The input traces must be run away from noise sources, such as digital lines, switching supplies or motor drive lines. Remember that these traces can contain high voltage, and must have the appropriate trace routing clearances. Because the sense traces only carry the amplifier bias current (approximately 7 µA at room temperature), the connecting input traces can be thinner, signal level traces. Excessive resistance in the trace must also be avoided. The paths of the traces must be identical, including connectors and vias, so that these errors are equal and cancel. The sense resistor heats up when the load increases. When the resistor heats up, the resistance generally goes up, which causes a change in the readings. The sense resistor must have as much heatsinking as possible to remove this heat through the use of heatsinks or large copper areas coupled to the resistor pads. A reading drifting over time after turn-on can usually be traced back to sense resistor heating. 11.2 Layout Example Figure 32. Kelvin or 4–Wire Connection to the Sense Resistor Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 21 LMP8480, LMP8481 SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 www.ti.com 12 Device and Documentation Support 12.1 Device Support 12.1.1 Development Support LMP8480/1 PSPICE Model LMP8480/1 TINA Reference Design TINA-TI SPICE-Based Analog Simulation Program LMP8480/1 Evaluation Boards product pages LMP8480/1 Evaluation Board Manual 12.2 Related Links The table below lists quick access links. Categories include technical documents, support and community resources, tools and software, and quick access to order now. Table 2. Related Links PARTS PRODUCT FOLDER ORDER NOW TECHNICAL DOCUMENTS TOOLS & SOFTWARE SUPPORT & COMMUNITY LMP8480 Click here Click here Click here Click here Click here LMP8481 Click here Click here Click here Click here Click here 12.3 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 12.4 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 12.5 Trademarks E2E is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. 12.6 Electrostatic Discharge Caution This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. 12.7 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 22 Submit Documentation Feedback Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 LMP8480, LMP8481 www.ti.com SNVS829E – MARCH 1999 – REVISED FEBRUARY 2017 13 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Copyright © 1999–2017, Texas Instruments Incorporated Product Folder Links: LMP8480 LMP8481 Submit Documentation Feedback 23 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LMP8480MM-T/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AV8A LMP8480MME-S/NOPB ACTIVE VSSOP DGK 8 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AY8A LMP8480MME-T/NOPB ACTIVE VSSOP DGK 8 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AV8A LMP8480MMX-S/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AY8A LMP8480MMX-T/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AV8A LMP8481MM-H/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AH9A LMP8481MM-S/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AA9A LMP8481MM-T/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AT9A LMP8481MME-H/NOPB ACTIVE VSSOP DGK 8 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AH9A LMP8481MME-S/NOPB ACTIVE VSSOP DGK 8 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AA9A LMP8481MME-T/NOPB ACTIVE VSSOP DGK 8 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AT9A LMP8481MMX-H/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AH9A LMP8481MMX-S/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AA9A LMP8481MMX-T/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 AT9A (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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