HCPL-7510

Isolated Linear Sensing IC

Data Sheet

Description

The HCPL-7510 isolated linearcurrent sensing IC family isdesigned for current sensing inlow-power electronic motordrives. In a typical

implementation, motor currentflows through an externalresistor and the resulting

analog voltage drop is sensedby the HCPL-7510. An outputvoltage is created on the otherside of the HCPL-7510 opticalisolation barrier. This single-ended output voltage isproportional to the motorcurrent. Since common-modevoltage swings of severalhundred volts in tens ofnanoseconds are common inmodern switching invertermotor drives, the HCPL-7510was designed to ignore veryhigh common-mode transientslew rates (of at least 10kV/µs).

The high CMR capability of theHCPL-7510 isolation amplifierprovides the precision andstability needed to accuratelymonitor motor current in highnoise motor control environ-ments, providing for smoothercontrol (less “torque ripple”)in various types of motorcontrol applications.

Functional Diagram

VDD1VIN+VIN–GND1IDD11234+–+–IDD28765VDD2VOUTVREFGND2SHIELDThe product can also be usedfor general analog signalisolation applications. Forgeneral applications, werecommend the HCPL-7510(gain tolerance of ±5%). TheHCPL-7510 utilizes sigma delta(S-D) analog-to-digitalconverter technology todelivery offset and gainaccuracy and stability overtime and temperature. Thisperformance is delivered in acompact, auto-insert, 8-pinDIP package that meets world-wide regulatory safetystandards. (A gull-wing

surface mount option #300 isalso available).

Features

•15 kV/µs common-mode rejectionat Vcm = 1000 V

•Compact, auto-insertable 8-pinDIP package

•60 ppm/°C gain drift vs.temperature

•–0.6 mV input offset voltage•8 µV/°C input offset voltage vs.temperature

•100 kHz bandwidth

•0.06% nonlinearity, single-endedamplifier output for low powerapplication.

•Worldwide safety approval:

UL 1577 (3750 Vrms/1 min.), CSAand IEC/EN/DIN EN 60747-5-2(Option 060 only)

•Advanced sigma-delta (Σ-∆)A/D converter technologyApplications

•Low-power inverter currentsensing

•Motor phase and rail currentsensing

•Switched mode power supplysignal isolation

•General purpose low-powercurrent sensing and monitoring•General purpose analog signalisolation

CAUTION: It is advised that normal static precautions be taken in handling and assembly ofthis component to prevent damage and /or degradation which may be induced by ESD.

Ordering Information

Specify part number followed by option number (if desired).Example:HCPL-7510-XXXXNo option = Standard DIP package, 50 per tube.300 = Gull Wing Surface Mount Option, 50 per tube.500 = Tape and Reel Packaging Option.060 = IEC/EN/DIN EN 60747-5-2 Option.XXXE = Lead Free Option

Package Outline DrawingsHCPL-7510 Standard DIP Package

9.80 ± 0.25(0.386 ± 0.010)8765A 7510DATE CODEYYWW12341.19 (0.047) MAX.1.78 (0.070) MAX.3.56 ± 0.13(0.140 ± 0.005)4.70 (0.185) MAX.0.51 (0.020) MIN.2.92 (0.115) MIN.1.080 ± 0.3200.65 (0.025) MAX.(0.043 ± 0.013)2.54 ± 0.25(0.100 ± 0.010)DIMENSIONS IN MILLIMETERS AND (INCHES).NOTE: FLOATING LEAD PROTUSION IS 0.5 mm (20 mils) MAX.2

7.62 ± 0.25(0.300 ± 0.010)6.35 ± 0.25(0.250 ± 0.010)5 TYP.0.20 (0.008)0.33 (0.013)HCPL-7510 Gull Wing Surface Mount Option 300 Outline Drawing

Land Pattern Recommendation9.80 ± 0.25(0.386 ± 0.010)87A 7510YYWW651.016 (0.040)6.350 ± 0.25(0.250 ± 0.010)10.9 (0.430)12342.0 (0.080)1.27 (0.050)1.780(0.070)MAX.9.65 ± 0.25(0.380 ± 0.010)7.62 ± 0.25(0.300 ± 0.010)1.19(0.047)MAX.3.56 ± 0.13(0.140 ± 0.005)0.20 (0.008)0.33 (0.013)1.080 ± 0.320(0.043 ± 0.013)2.54(0.100)BSCDIMENSIONS IN MILLIMETERS (INCHES).TOLERANCES (UNLESS OTHERWISE SPECIFIED):0.635 ± 0.130(0.025 ± 0.005)0.635 ± 0.25(0.025 ± 0.010)12 NOM.NOTE: FLOATING LEAD PROTUSION IS 0.5 mm (20 mils) MAX.xx.xx = 0.01xx.xxx = 0.005LEAD COPLANARITY MAXIMUM: 0.102 (0.004)3

Solder Reflow Temperature Profile

300PREHEATING RATE 3˚C + 1˚C/–0.5˚C/SEC.REFLOW HEATING RATE 2.5˚C ± 0.5˚C/SEC.PEAKTEMP.245˚CPEAKTEMP.240˚C200TEMPERATURE (˚C)PEAKTEMP.230˚C2.5˚C ± 0.5˚C/SEC.160˚C150˚C140˚C3˚C + 1˚C/–0.5˚C30SEC.30SEC.SOLDERINGTIME200˚C100PREHEATING TIME150˚C, 90 + 30 SEC.50 SEC.TIGHTTYPICALLOOSE050ROOM TEMPERATURE0100TIME (SECONDS)150200250Recommended Pb-Free IR Profile

TIME WITHIN 5 ˚C of ACTUALPEAK TEMPERATURE20-40 SEC.tpTp217 ˚CTLTsmaxTsmin260 +0/-5 ˚CTEMPERATURE (˚C)RAMP-UP3 ˚C/SEC. MAX.150 - 200 ˚CRAMP-DOWN6 ˚C/SEC. MAX.tsPREHEAT60 to 180 SEC.25t 25 ˚C to PEAKtL60 to 150 SEC.TIME (SECONDS)NOTES:THE TIME FROM 25 ˚C to PEAK TEMPERATURE = 8 MINUTES MAX.Tsmax = 200 ˚C, Tsmin = 150 ˚C4

Regulatory Information

The HCPL-7510 has been approved by the following organizations:IEC/EN/DIN EN 60747-5-2Approved under:

IEC 60747-5-2:1997 + A1:2002EN 60747-5-2:2001 + A1:2002

DIN EN 60747-5-2 (VDE 0884 Teil 2):2003-01.

UL

Approved under UL 1577, component recognitionprogram up to VISO = 3750 VRMS. File E55361.CSA

Approved under CSA Component AcceptanceNotice #5, File CA 88324.

IEC/EN/DIN EN 60747-5-2 Insulation Characteristics[1]Description

Installation classification per DIN EN 0110-1/1997-04, Table 1for rated mains voltage - 150 Vrmsfor rated mains voltage - 300 Vrmsfor rated mains voltage - 600 VrmsClimatic Classification

Pollution Degree (DIN EN 0110-1/1997-04)Maximum Working Insulation Voltage

Input to Output Test Voltage, Method b[2]

VIORM x 1.875 = VPR, 100% production test with tm = 1 sec, partial discharge <5 pCInput to Output Test Voltage, Method a[2]

VIORM x 1.5 = VPR, type and sample test, tm = 60 sec, partial discharge <5 pCHighest Allowable Overvoltage (transient overvoltage tini = 10 sec)Safety-limiting values – maximum values allowed in the event of a failure.Case TemperatureInput Current[3]Output Power[3]Insulation Resistance at TS, VIO = 500 V

Notes:

1. Insulation characteristics are guaranteed only within the safety maximum ratings which must beensured by protective circuits within the application. Surface Mount Classifications is Class A inaccordance with CECC00802.

2. Refer to the optocoupler section of the Isolation and Control Components Designer’s Catalog,under Product Safety Regulations section,

(IEC/EN/DIN EN 60747-5-2) for a detailed description of Method a and Method b partialdischarge test profiles.

3. Refer to the following figure for dependence of PS and IS on ambient temperature.

SymbolCharacteristicUnitI – IVI – IIII – II55/100/212

VIORMVPRVPRVIOTM

891167013366000

VpeakVpeakVpeakVpeak°CmAmWΩ

TS175IS, INPUT400PS, OUTPUT600RS

800>109

OUTPUT POWER – PS, INPUT CURRENT – IS70060050040030020010000255075PS (mW)IS (mA)100125150175200TS – CASE TEMPERATURE – C5

Insulation and Safety Related SpecificationsParameter

Minimum External Air Gap(clearance)

Minimum External Tracking(creepage)

Minimum Internal Plastic Gap(internal clearance)Tracking Resistance

(comparative tracking index)Isolation Group

CTISymbolL(101)L(102)

Value7.48.00.5

Unitmmmmmm

Conditions

Measured from input terminals to output terminals,shortest distance through air.

Measured from input terminals to output terminals,shortest distance path along body.

Through insulation distance conductor to conductor,usually the straight line distance thickness between theemitter and detector.DIN IEC 112 Part 1

Material Group (DIN EN 0110-1/1997-04)

>175IIIa

V

Absolute Maximum RatingsParameter

Storage TemperatureOperating TemperatureSupply Voltage

Steady-State Input VoltageTwo Second Transient Input VoltageOutput VoltageReference Input VoltageReference Input CurrentLead Solder TemperatureSolder Reflow Temperature Profile

SymbolTSTA

VDD1_max, VDD1_maxVIN+, VIN-VIN+, VIN-VOUTVREFIREF

See Package Outline Drawings section

Min.–55–400–2.0–6.0–0.50.0

Max.1251006VDD1 + 0.5-VDD1 + 0.5-VDD2 + 0.5-VDD2 + 0.5-20-Units°C°CVVVVVmA

Note

260°C for 10 sec., 1.6 mm below seating plane

Recommended Operating ConditionsParameter

Operating TemperatureSupply Voltage

Input Voltage (accurate and linear)Input Voltage (functional)Reference Input Voltage

SymbolTA

VDD1, VDD2VIN+, VIN-VIN+, VIN-VREF

Min.–404.5–200–2.04.0

Max.855.52002.0VDD2

Units°CVmVVV

Note

6

Electrical Specifications (DC)

Unless otherwise noted, all typicals and figures are at the nominal operation conditions of VIN+ = 0V, VIN- = 0V,VREF = 4.0V, VDD1 = VDD2 = 5.0 V and TA = 25°C; all Minimum/Maximum specifications are within the RecommendedOperating Conditions.ParameterInput Offset VoltageMagnitude of Input OffsetChange vs. TemperatureGain

SymbolVOS∆Vos/∆TG

VREF/0.512– 3%

600.060.0004Min.–6Typ.–18Max.620VREF/0.512+ 3%3000.55

UnitsmVµV/°CV/V

Test

ConditionsVIN+ = 0VFig.67-0.2 V < VIN+8< 0.2 VTA = 25°C-0.2 V < VIN+9< 0.2 V-0.2 V < VIN+10< 0.2 V-0.2 V < VIN+11< 0.2 V-0.1 V < VIN+< 0.1 V

1,2,31,2,3

3,53,42Note1Magnitude of Gain Changevs. TemperatureVOUT 200 mV NonlinearityMagnitude of VOUT 200 mVNonlinearity Changevs. TemperatureVOUT 100 mV NonlinearityInput Supply CurrentOutput Supply CurrentReference Voltage InputCurrentInput CurrentMagnitude of Input BiasCurrent vs. TermperatureCoefficient

Maximum Input Voltagebefore VOUT ClippingEquivalent Input ImpedanceVOUT Output ImpedanceInput DC Common-ModeRejection Ratio

∆G/∆TNL200

|dNL200/dT|ppm/°C%%/°CNL100IDD1IDD2IREFIIN+|dIIN/dT|0.0411.79.90.26–0.60.450.4161615%mAmAmAµAnA/°CVIN+ = 0 V4|VIN+|MAXRINROUTCMRRIN

2567001563

mVkΩΩdB

5

7

7

Switching Specifications (AC)

Over recommended operating conditions unless otherwise specified.Parameter

VIN to VOUT Signal Delay (50 – 10%)VIN to VOUT Signal Delay (50 – 50%)VIN to VOUT Signal Delay (50 – 90%)VOUT Rise Time (10 – 90%)VOUT Fall Time (10 – 90%)VOUT Bandwidth (-3 dB)VOUT Noise

Common Mode TransientImmunity

SymbolMin.tPD10tPD50tPD90tRtFBWNOUTCMTI

1050

Typ.2.23.45.23.03.210031.515

Max.459.977

UnitsµsµsµsµsµskHzkV/µs

VIN+ = 200 mVpk-pkTA = 25°C, VCM = 1000 V

1415

mVrmsVIN+ = 0 V

Test Conditions

VIN+ = 0 mV to 200 mV step

Fig.Note13

Package CharacteristicsParameter

Input-Output MomentaryWithstand VoltageInput-Output ResistanceInput-Output Capacitance

SymbolVISORI-OCI-O

Min.3750

>1091.4Typ.

Max.

UnitsVrmsΩpF

Test ConditionsTA = 25°C, RH < 50%VI-O = 500 VFreq = 1 MHz

Fig.

Note6

Notes:

General Note: Typical values were taken from a sample of nominal units operating at nominal conditions (VDD1 = VDD2 = 5 V, VREF = 4.0 V, Temperature =25°C) unless otherwise stated. Nominal plots shown from Figure 1 to 11 represented the drift of these nominal units from their nominal operatingconditions.

1.Input Offset Voltage is defined as the DC Input Voltage required to obtain an output voltage of VREF/2.

2.Gain is defined as the slope of the best-fit line of the output voltage vs. the differential input voltage (VIN+ - VIN-) over the specified input range. Gainis derived from VREF/512 mV; e.g. VREF = 5.0, gain will be 9.77 V/V.

3.Nonlinearity is defined as half of the peak-to-peak output deviation from the best-fit gain line, expressed as a percentage of the full-scale outputvoltage range.

4.NL200 is the nonlinearity specified over an input voltage range of ±200 mV.5.NL100 is the nonlinearity specified over an input voltage range of ±100 mV.

6.In accordance with UL1577, each optocoupler is proof tested by applying an insulation test voltage •4500 Vrms for 1 second (leakage detection currentlimit, II-O < 5 µA). This test is performed before the 100% production test for the partial discharge (method b) shown inIEC/EN/DIN EN 60747-5-2 Insulation Characteristic Table, if applicable.

7. CMRR is defined as the ratio of the differential signal gain (signal applied differentially between pins 2 and 3) to the common-mode gain (input pinstied together and the signal applied to both inputs at the same time), expressed in dB.

8

13

Am12

– TNERR11

UC YLPP10

US – DI9DD1 DIIDD2 84.54.74.95.15.35.5VDD – SUPPLY VOLTAGE – V

Figure 1. Supply current vs. supply voltage.0.20Aµ -0.2– TNE-0.4RRUC-0.6 TUPN-0.8I – N-1.0II-1.2-1.4-0.3-0.2-0.100.10.20.3VIN – INPUT VOLTAGE – VFigure 4. Input current vs. input voltage.2.0VTYPICALm1.5 –MAXIMUM EG1.0NAHC0.5 TESF0FO TU-0.5PNI –-1.0 SOV∆-1.5-2.0-40-20020406080100TA – TEMPERATURE – C

Figure 7. Input offset change vs. temperature.9

11.010.5

Am –10.0 TNE9.5RRUC 9.0YLPP8.5US I–DD1 D8.0DIIDD2 7.5

7.0-40-20020406080100TA – TEMPERATURE – C

Figure 2. Supply current vs. temperature.4.03.5V –3.0 EGAT2.5LOV T2.0UPTU1.5O – O1.0V0.50-0.3-0.2-0.100.10.20.3VIN – INPUT VOLTAGE – VFigure 5. Output voltage vs. input voltage.

0.020V0.015DD1 % –VDD2 EGN0.010AHC N0.005IAG – N0IAG∆-0.005-0.0104.54.74.95.15.35.5VDD – SUPPLY VOLTAGE – VFigure 8. Gain change vs. supply voltage.12.011.0Am –10.0 TNE9.0RRUC 8.0YLPP7.0US I– D6.0DD1 DIIDD2 5.04.0-0.3-0.2-0.100.10.20.3VIN – INPUT VOLTAGE – VFigure 3. Supply current vs. input voltage.

2.5Vµ2.0 –V EG1.5DD1 NVAH1.0DD2 C TE0.5SFFO 0TUPN-0.5I – S-1.0OVD-1.5-2.04.54.74.95.15.35.5VDD – SUPPLY VOLTAGE – VFigure 6. Input offset change vs. supplyvoltage.

0.70.6%0.5 – EG0.4NA0.3HC N0.2IAG 0.1– NIA0G∆-0.1-0.2

-0.3-40

-20

0

20

40

60

80

100

TA – TEMPERATURE – C

Figure 9. Gain change vs. temperature.

0.0500.09NL – NONLINEARITY – %0.048NL – NONLINEARITY – %0.080.0460.070.044VDD1 VDD2 4.74.95.15.35.50.0420.0404.50.060.05-40-20020406080100VDD – SUPPLY VOLTAGE – VTA – TEMPERATURE – CFigure 10. Nonlinearity vs. supply voltage.Figure 11. Nonlinearity vs. temperature.

VDD1VDD2TPD – PROPAGATION DELAY – µs6543210-40Tp5010 Tp5050 Tp5090 Trise -20020406080100TA – TEMPERATURE – C180.1 µFVIN2HCPL-751070.1 µFVOUT0.1 µF36VREF45Figure 12. Propagation delay test circuit.Figure 13. Propagation delay vs. temperature.

78L05IN OUT10-1VDD20.1µF0.1µF180.1 µF27HCPL-751036VOUTGAIN – dB-2-3-4-5-60.19 VVREF45PULSE GEN.1.010.0100.01000.0FREQUENCY – kHz+–VCMFigure 14. Bandwidth.Figure 15. CMTI test circuit.

10

Application Information

Power Supplies and BypassingThe recommended supplyconnections are shown inFigure 16. A floating powersupply (which in many

applications could be the samesupply that is used to drivethe high-side power transistor)is regulated to 5 V using asimple zener diode (D1); thevalue of resistor R4 should bechosen to supply sufficientcurrent from the existingfloating supply. The voltagefrom the current sensing

resistor (Rsense) is applied to

the input of the HCPL-7510through an RC anti-aliasingfilter (R2 and C2). Althoughthe application circuit isrelatively simple, a few

recommendations should befollowed to ensure optimalperformance.

The power supply for theHCPL-7510 is most often

obtained from the same supplyused to power the power

transistor gate drive circuit. Ifa dedicated supply is required,in many cases it is possible toadd an additional winding onan existing transformer.

Otherwise, some sort of simpleisolated supply can be used,such as a line poweredtransformer or a high-frequency DC-DC converter.An inexpensive 78L05 three-terminal regulator can also beused to reduce the floatingsupply voltage to 5 V. To helpattenuate high- frequencypower supply noise or ripple,a resistor or inductor can beused in series with the inputof the regulator to form alow-pass filter with theregulator’s input bypasscapacitor.

HV+GATE DRIVECIRCUIT+FLOATINGPOSITIVESUPPLY-R4R2MOTOR39 Ω+R1-RSENSED15.1 VC10.1 µF1VDD12VIN+3VIN-4GND1HCPL-7510C20.01 µFHV-Figure 16. Recommended supply and sense resistor connections.

11

As shown in Figure 17, 0.1 µFbypass capacitors (C1, C2)should be located as close aspossible to the pins of theHCPL-7510. The bypasscapacitors are requiredbecause of the high-speeddigital nature of the signalsinside the HCPL-7510. A 0.01µF bypass capacitor (C2) isalso recommended at theinput due to the switched-capacitor nature of the inputcircuit. The input bypasscapacitor also forms part ofthe anti-aliasing filter, whichis recommended to preventhigh frequency noise fromaliasing down to lower

frequencies and interferingwith the input signal. Theinput filter also performs animportant reliability function—itreduces transient spikes fromESD events flowing through thecurrent sensing resistor.PC Board Layout

The design of the printedcircuit board (PCB) shouldfollow good layout practices,such as keeping bypass

capacitors close to the supplypins, keeping output signalsaway from input signals, theuse of ground and powerplanes, etc. In addition, thelayout of the PCB can also

affect the isolation transientimmunity (CMTI) of the

HCPL-7510, due primarily tostray capacitive couplingbetween the input and theoutput circuits. To obtain

optimal CMTI performance, thelayout of the PC board shouldminimize any stray couplingby maintaining the maximumpossible distance between theinput and output sides of thecircuit and ensuring that anyground or power plane on thePC board does not pass

directly below or extend muchwider than the body of theHCPL-7510.

FLOATINGPOSITIVESUPPLYHV+GATE DRIVECIRCUITU178L05IN OUTC10.1 µFMOTORC20.1 µFR568 Ω+R1-RSENSEHCPL-7510C6 = 150 pFC4 = C5 = 0.1 µFC30.01 µF+5 V1VDD12VIN+3VIN-4GND1VDD28VOUT7VREF6GND25C4C5C6A/DVREFGNDµCHV-Figure 17. Recommended HCPL-7510 application circuit.

12

Current Sensing Resistors

The current sensing resistorshould have low resistance (tominimize power dissipation),low inductance (to minimizedi/dt induced voltage spikeswhich could adversely affectoperation), and reasonabletolerance (to maintain overallcircuit accuracy). Choosing aparticular value for theresistor is usually acompromise between

minimizing power dissipationand maximizing accuracy.Smaller sense resistance

decreases power dissipation,while larger sense resistancecan improve circuit accuracyby utilizing the full inputrange of the HCPL-7510.The first step in selecting asense resistor is determininghow much current the resistorwill be sensing. The graph inFigure 18 shows the RMScurrent in each phase of athree-phase induction motoras a function of average motoroutput power (in horsepower,hp) and motor drive supplyvoltage. The maximum valueof the sense resistor isdetermined by the currentbeing measured and the

maximum recommended inputvoltage of the isolation

amplifier. The maximum senseresistance can be calculated bytaking the maximum

recommended input voltageand dividing by the peak

current that the sense resistorshould see during normaloperation. For example, if amotor will have a maximumRMS current of 10 A and canexperience up to 50%overloads during normaloperation, then the peak

current is 21.1 A (=10 x 1.414x 1.5). Assuming a maximuminput voltage of 200 mV, themaximum value of sense

13

resistance in this case wouldbe about 10 mΩ. Themaximum average powerdissipation in the senseresistor can also be easilycalculated by multiplying thesense resistance times thesquare of the maximum RMScurrent, which is about 1 W inthe previous example. If thepower dissipation in the senseresistor is too high, the

resistance can be decreasedbelow the maximum value todecrease power dissipation.The minimum value of thesense resistor is limited byprecision and accuracy

requirements of the design. Asthe resistance value is

reduced, the output voltageacross the resistor is also

reduced, which means that theoffset and noise, which arefixed, become a largerpercentage of the signal

amplitude. The selected valueof the sense resistor will fallsomewhere between theminimum and maximumvalues, depending on theparticular requirements of aspecific design.

When sensing currents largeenough to cause significantheating of the sense resistor,the temperature coefficient(tempco) of the resistor canintroduce nonlinearity due tothe signal dependenttemperature rise of the

resistor. The effect increasesas the resistor-to-ambientthermal resistance increases.This effect can be minimizedby reducing the thermalresistance of the current

sensing resistor or by using aresistor with a lower tempco.Lowering the thermal

resistance can be accomplishedby repositioning the currentsensing resistor on the PCboard, by using larger PCboard traces to carry away

more heat, or by using a heatsink. For a two-terminal

current sensing resistor, as thevalue of resistance decreases,the resistance of the leadsbecome a significantpercentage of the totalresistance. This has twoprimary effects on resistoraccuracy. First, the effectiveresistance of the sense resistorcan become dependent onfactors such as how long theleads are, how they are bent,how far they are inserted intothe board, and how far solderwicks up the leads duringassembly (these issues will bediscussed in more detail

shortly). Second, the leads aretypically made from amaterial, such as copper,which has a much higher

tempco than the material fromwhich the resistive elementitself is made, resulting in ahigher tempco overall. Both ofthese effects are eliminatedwhen a four-terminal currentsensing resistor is used. Afour-terminal resistor has twoadditional terminals that areKelvin-connected directlyacross the resistive elementitself; these two terminals areused to monitor the voltageacross the resistive elementwhile the other two terminalsare used to carry the loadcurrent. Because of the Kelvinconnection, any voltage dropsacross the leads carrying theload current should have noimpact on the measuredvoltage.

40RE440WO35380PE220SR30120OH –25 REW20OP TU15PTUO10 ROTO5M005101520253035MOTOR PHASE CURRENT – A (rms)

Figure 18. Motor output horsepower vs. motorphase current and supply voltage.

When laying out a PC boardfor the current sensing

resistors, a couple of pointsshould be kept in mind. TheKelvin connections to theresistor should be brought

together under the body of theresistor and then run veryclose to each other to theinput of the HCPL-7510; thisminimizes the loop area of theconnection and reduces thepossibility of stray magneticfields from interfering with themeasured signal. If the senseresistor is not located on thesame PC board as the HCPL-7510 circuit, a tightly twistedpair of wires can accomplishthe same thing. Also, multiplelayers of the PC board can be

14

used to increase currentcarrying capacity. Numerousplated-through vias shouldsurround each non-Kelvinterminal of the sense resistorto help distribute the currentbetween the layers of the PCboard. The PC board shoulduse 2 or 4 oz. copper for thelayers, resulting in a currentcarrying capacity in excess of20 A. Making the currentcarrying traces on the PCboard fairly large can alsoimprove the sense resistor’spower dissipation capability byacting as a heat sink. Liberaluse of vias where the loadcurrent enters and exits thePC board is alsorecommended.

Sense Resistor Connections

The recommended method forconnecting the HCPL-7510 tothe current sensing resistor isshown in Figure 17. VIN+ (pin2 of the HPCL-7510) isconnected to the positive

terminal of the sense resistor,while VIN- (pin 3) is shortedto GND1 (pin 4), with thepowersupply return pathfunctioning as the sense lineto the negative terminal of thecurrent sense resistor. Thisallows a single pair of wiresor PC board traces to connect

the HCPL-7510 circuit to thesense resistor. By referencingthe input circuit to thenegative side of the senseresistor, any load currentinduced noise transients onthe resistor are seen as a

common- mode signal and willnot interfere with the current-sense signal. This is importantbecause the large load

currents flowing through themotor drive, along with theparasitic inductances inherentin the wiring of the circuit,can generate both noise spikesand offsets that are relativelylarge compared to the smallvoltages that are being

measured across the currentsensing resistor. If the samepower supply is used both forthe gate drive circuit and forthe current sensing circuit, itis very important that theconnection from GND1 of theHCPL-7510 to the senseresistor be the only returnpath for supply current to thegate drive power supply inorder to eliminate potentialground loop problems. The

only direct connection betweenthe HCPL-7510 circuit and thegate drive circuit should bethe positive power supply line.

FREQUENTLY ASKED QUESTIONS ABOUT THE HCPL-75101. THE BASICS

1.1: Why should I use the HCPL-7510 for sensing current when Hall-effect sensors are available which don’t need anisolated supply voltage?

Available in an auto-insertable, 8-pin DIP package, the HCPL-7510 is smaller than and has betterlinearity, offset vs. temperature and Common Mode Rejection (CMR) performance than most Hall-effect sensors. Additionally, often the required input-side power supply can be derived from thesame supply that powers the gate-drive optocoupler.2. SENSE RESISTOR AND INPUT FILTER

2.1: Where do I get 10 mΩ resistors? I have never seen one that low.

Although less common than values above 10 Ω, there are quite a few manufacturers of resistorssuitable for measuring currents up to 50 A when combined with the HCPL-7510. Example productinformation may be found at Dale’s web site (http://www.vishay.com/vishay/dale) and Isotek’s website (http://www.isotekcorp.com) and Iwaki Musen Kenkyusho’s website (http://www.iwakimusen.co.jp) and Micron Electric’s website (http://www.micron-e.co.jp).2.2: Should I connect both inputs across the sense resistor instead of grounding VIN- directly to pin 4?

This is not necessary, but it will work. If you do, be sure to use an RC filter on both pin 2 (VIN+)and pin 3 (VIN-) to limit the input voltage at both pads.

2.3: Do I really need an RC filter on the input? What is it for? Are other values of R and C okay?

The input anti-aliasing filter (R=39 Ω, C=0.01 µF) shown in the typical application circuit isrecommended for filtering fast switching voltage transients from the input signal.

(This helps to attenuate higher signal frequencies which could otherwise alias with the inputsampling rate and cause higher input offset voltage.)

Some issues to keep in mind using different filter resistors or capacitors are:

1. (Filter resistor:) The equivalent input resistance for HCPL-7510 is around 700 kΩ. It is

therefore best to ensure that the filter resistance is not a significant percentage of this value;otherwise the offset voltage will be increased through the resistor divider effect. [As an

example, if Rfilt = 5.5 kΩ, then VOS = (Vin * 1%) = 2 mV for a maximum 200 mV input andVOS will vary with respect to Vin.]2. The input bandwidth is changed as a result of this different R-C filter configuration. In fact thisis one of the main reasons for changing the input-filter R-C time constant.3. (Filter capacitance:) The input capacitance of the HCPL-7510 is approximately 1.5 pF. Forproperoperation the switching input-side sampling capacitors must be charged from arelatively fixed (low impedance) voltage source. Therefore, if a filter capacitor is used it is bestfor this capacitor to be a few orders of magnitude greater than the CINPUT (A value of at least100 pF works well.)2.4: How do I ensure that the HCPL-7510 is not destroyed as a result of short circuit conditions whichvoltage drops across the sense resistor that exceed the ratings of the HCPL-7510’s inputs?

cause

Select the sense resistor so that it will have less than 5 V drop when short circuits occur. Theonly other requirement is to shut down the drive before the sense resistor is damaged or itssolder joints melt. This ensures that the input of the HCPL-7510 can not be damaged by senseresistors going open-circuit.3. ISOLATION AND INSULATION

3.1: How many volts will the HCPL-7510 withstand?

The momentary (1 minute) withstand voltage is 3750 V rms per UL 1577 and CSA ComponentAcceptance Notice #5.

15

4. ACCURACY

4.1: Does the gain change if the internal LED light output degrades with time?

No. The LED is used only to transmit a digital pattern. Agilent has accounted for LED degradationin the design of the product to ensure long life.5. MISCELLANEOUS

5.1: How does the HCPL-7510 measure negative signals with only a +5 V supply?

The inputs have a series resistor for protection against large negative inputs. Normal signals areno more than 200 mV in amplitude. Such signals do not forward bias any junctions sufficiently tointerfere with accurate operation of the switched capacitor input circuit.

www.agilent.com/semiconductors

For product information and a complete listof distributors, please go to our web site.For technical assistance call:Americas/Canada: +1 (800) 235-0312or (916) 788-6763Europe: +49 (0) 6441 92460China: 10800 650 0017Hong Kong: (+65) 6756 2394

India, Australia, New Zealand: (+65) 6755 1939Japan: (+81 3) 3335-8152(Domestic/Inter-national), or 0120-61-1280(Domestic Only)Korea: (+65) 6755 1989

Singapore, Malaysia, Vietnam, Thailand,Philippines, Indonesia: (+65) 6755 2044Taiwan: (+65) 6755 1843Data subject to change.

Copyright © 2005 Agilent Technologies, Inc.February 2, 2005

obsoletes 5989-0317EN5989-2162EN