acpl-782t

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ACPL-782TAutomotive Isolation Ampliferwith R2Coupler Isolation

Data Sheet

CAUTION: It is advised that normal static precautions be taken in handling and assembly

of this component to prevent damage and/or degradation which may be induced by ESD.

Description

The ACPL-782T isolation amplifer was designed orvoltage and current sensing in electronic motor drivesand battery system monitoring. In a typical implementa-tion, and motor currents ow through an external resistorand the resulting analog voltage drop is sensed by theACPL-782T. A dierential output voltage is created on theother side o the ACPL-782T optical isolation barrier. Thisdierential output voltage is proportional to the motorcurrent and can be converted to a single-ended signalby using an op-amp as shown in the recommended ap-plication circuit. Since common-mode voltage swingso several hundred volts in tens o nanoseconds arecommon in modern switching inverter motor drives, theACPL-782T was designed to ignore very high common-mode transient slew rates (o at least 10 kV/Ps).

The high CMR capability o the ACPL-782T isolationamplifer provides the precision and stability needed to ac-curately monitor motor current and DC rail voltage in highnoise motor control environments, providing or smoother

control (lesstorque ripple) in various types o motor controlapplications.

The product can also be used or general analog signalisolation applications requiring high accuracy, stability,and linearity under similarly severe noise conditions. TheACPL-782T utilizes sigma delta (6') analog-to-digitalconverter technology, chopper stabilized amplifers, anda ully dierential circuit topology.

Together, these eatures deliver unequaled isolation-mode noise rejection, as well as excellent oset andgain accuracy and stability over time and temperature.

This perormance is delivered in a compact, auto-insert-able, industry standard 8-pin DIP package that meetsworldwide regulatory saety standards. (A gull-wingsurace mount option -300E is also available).

Avago R2Coupler isolation products provide the rein-orced insulation and reliability needed or critical in auto-motive and high temperature industrial applications.

Features

x 2% Gain Tolerance @ 25C

x 15 kV/Ps Common-Mode Rejection at VCM = 1000V

x 30ppm/C Gain Drit vs. Temperature

x 0.3 mV Input Oset Voltage

x 100 kHz Bandwidth

x 0.004% Nonlinearity

x Compact, Auto-Insertable Standard 8-pin DIP Package

x Worldwide Saety Approval: UL 1577 (3750 VRMS/1 min.) and CSA IEC 60747-5-5, DIN EN 60747-5-2(VDE 0884 Teil 2)

x Qualifed to AEC-Q100 Test Guidelines

x Automotive Operating Temperature -40 to 125C

x Advanced Sigma-Delta (6') A/D Converter Technology

x Fully Dierential Circuit Topology

Applications

x Automotive Motor Inverter Current/Voltage Sensingx Automotive AC/DC and DC/DC converter Current/

Voltage sensing

x Automotive Battery ECU

x Automotive Motor Phase Current Sensing

x Isolation Interace or Temperature Sensing

x General Purpose Current Sensing and Monitoring

Functional Diagram

Lead (Pb) Free

RoHS 6 fullycompliant

RoHS 6 ully compliantoptionsavailable;-xxxE denotesa lead-reeproduct

The connection o a 0.1 PF bypass capacitor betweenpins 1 and 4, pins 5 and 8 is recommended.

1

2

3

4

8

7

6

5

IDD1VDD1

VIN+

VIN-

GND1

IDD2VDD2

VOUT+

VOUT-

GND2

+

-

+

-

SHIELD

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Part Number

Option

(RoHS Compliant) Package Surace Mount Gullwing Tape & Reel

ACPL-782T

-000E

300mil DIP-8

-300E X X

-500E X X X

To order, choose a part number rom the part number column and combine with the desired option rom the optioncolumn to orm an order entry.

Example:

ACPL-782T-500E to order product o gullwing SMT DIP-8 package in Tape and Reel packaging with RoHS compliant.

Option datasheets are available. Contact your Avago sales representative or authorized distributor or inormation.

Package Outline Drawings

ACPL-782T-000E Standard DIP Package

9.80 0.25(0.386 0.010)

1.78 (0.070) MAX.1.19 (0.047) MAX.

A 782T

YYWWEE

DATE CODE

EXTENDEDDATE CODE

1.080 0.320(0.043 0.013)

2.54 0.25(0.100 0.010)

0.51 (0.020) MIN.

0.65 (0.025) MAX.

4.70 (0.185) MAX.

2.92 (0.115) MIN.

Dimensions in millimeters and (inches).

Note:Floating lead protrusion is 0.5 mm (20 mils) max.

5678

4321

5 TYP.0.20 (0.008)0.33 (0.013)

7.62 0.25(0.300 0.010)

6.35 0.25

(0.25

0 0.010)

3.56 0.13(0.140 0.005)

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Gull Wing Surace Mount Option 300E and 500E

0.635 0.25(0.025 0.010)

12 NOM.

9.65 0.25(0.380 0.010)

0.635 0.130(0.025 0.005)

7.62 0.25

(0.300 0.010)

5678

4321

9.80 0.25(0.386 0.010)

6.350 0.25(0.250 0.010)

1.016 (0.040)

1.27 (0.050)

10.9 (0.430)

2.0 (0.080)

LAND PATTERN RECOMMENDATION

1.080 0.320(0.043 0.013)

3.56 0.13(0.140 0.005)

1.780(0.070)

MAX.1.19

(0.047

)MAX.

2.54(0.100)

BSC

Note: Floating lead protrusion is 0.5 mm (20 mils) max.

Dimensions in millimeters (inches).Tolerances (unless otherwise specifed): xx.xx = 0.01

xx.xxx = 0.005

A 782T

YYWWEE

LEAD COPLANARITYMAXIMUM: 0.102 (0.004)

0.20 (0.008)0.33 (0.013)

ULUL 1577, component recognition program up to VISO =3750 VRMS

CSA

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

IEC/DINIEC 60747-5-5

DIN EN 60747-5-2(VDE 0884 Teil 2)

Regulatory Inormation

The ACPL-782T-000E is approved by the ollowing organizations:

Recommended Pb-Free IR Profle

Recommended reow condition as per JEDEC Standard, J-STD-020 (latest revision). Non-Halide Flux should be used.

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IEC 60747-5-5, DIN EN 60747-5-2(VDE 0884 Teil 2) Insulation Characteristics

Description Symbol Characteristic Unit

Installation classifcation per DIN VDE 0110/1.89, Table 1

or rated mains voltage 300 Vrms



I-IV

I-III

I-II

Climatic Classifcation 55/125/21

Pollution Degree (DIN VDE 0110/1.89) 2

Maximum Working Insulation Voltage VIORM 891 VPEAK

Input to Output Test Voltage, Method b[2] VIORM x 1.875 = VPR,

100% Production Test with tm = 1 sec, Partial discharge < 5 pC

VPR 1670 VPEAK

Input to Output Test Voltage, Method a[2] VIORM x 1.6 = VPR,

Type and Sample Test, tm = 60 sec, Partial discharge < 5 pC

VPR 1426 VPEAK

Highest Allowable Overvoltage (Transient Overvoltage tini = 60 sec) VIOTM 6000 VPEAK

Saety-limiting valuesmaximum values allowed in the event o a ailure.

Case Temperature

Input Current[3]

Output Power[3]

TSIS,INPUTPS,OUTPUT

175

400

600

C

mA

mW

Insulation Resistance at TS , VIO = 500 V RS >109 :

Notes:1. Insulation characteristics are guaranteed only within the saety maximum ratings which must be ensured by protective circuits within the

application. Surace Mount Classifcation is Class A in accordance with CECC00802.2. Reer to the optocoupler section o the Isolation and Control Components Designers Catalog, under Product Saety Regulations section, (IEC

60747-5-5/DIN EN 60747-5-2) or a detailed description o Method a and Method b partial discharge test profles.3. Reer to the ollowing fgure or dependence o PS and IS on ambient temperature.

OUTPUTPOWER-PS,

INPUTCURRENT-IS

00

TA - CASE TEMPERATURE - C

20050

400

12525 75 100 150

600

800

200

100

300

500

700

175

PS (mW)

IS (mA)

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Insulation and Saety Related Specifcations

Parameter Symbol Value Units Conditions

Minimum ExternalAir Gap (Clearance)

L(101) 7.4 mm Measured rom input terminals to output terminals,shortest distance through air.

Minimum ExternalTracking (Creepage)

L(102) 8.0 mm Measured rom input terminals to output terminals,shortest distance path along body.

Minimum InternalPlastic Gap(Internal Clearance)

0.5 mm Through insulation distance conductor to conductor,usually the straight line distance thickness betweenthe emitter and detector.

Tracking Resistance(ComparativeTracking Index)

CTI >175 Volts DIN IEC 112/VDE 0303 Part 1

Isolation Group(DIN VDE0109)

IIIa Material Group (DIN VDE 0110)

Absolute Maximum Ratings

Parameter Symbol Min. Max. Units

Storage Temperature TS -55 130 C

Operating Temperature TA -40 125 C

Supply Voltage VDD1, VDD2 0 5.5 Volts

Steady-state Input Voltage VIN+, VIN- -2.0 VDD1 + 0.5 Volts

2 second Transient Input Voltage -6.0 Volts

Output Voltage VOUT -0.5 VDD2 + 0.5 Volts

Solder Reow Temperature Profle See Package Outline Drawings Section

Recommended Operating Conditions

Parameter Symbol Min. Max. Units Notes

Ambient Operating Temperature TA -40 125 C

Power Supply Voltage VDD1, VDD2 4.5 5.5 Volts

Input Voltage (Accurate & Linear) VIN+, VIN- -200 200 mV 1

Input Voltage (Functional) VIN+, VIN- -2 2 V

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DC Electrical Specifcations

Unless otherwise noted, all typical and fgures are at the nominal operating conditions o VIN+ = 0, VIN- = 0 V, VDD1 = VDD2= 5 V and TA = 25C; all Min. /Max. Specifcations are within the Recommended Operating Conditions.

Parameter Symbol Min. Typ.* Max. Units Test Conditions Fig. Note

Input Oset Voltage VOS -2.0 0.3 2.0 mV TA=25C 1,2

-4.0 4.0 mV -40C < TA < +125C,-4.5V < (VDD1, VDD2) < 5.5V

Magnitude o InputOset Change vs.Temperature

|'VOS/'TA| 3.0 10.0 PV/C 3 2

Gain G 7.84 8.00 8.16 V/V -200 mV < VIN+ < 200 mV,TA = 25C,

4,5,6 3

Magnitude o VOUTGain Change vs.Temperature

|'G/G/'TA|

30 PPM/C 4

VOUT 200 mVNonlinearity

NL200 0.0037 0.35 % -200 mV < VIN+ < 200 mV 7,8 5

Magnitude o VOUT200mV NonlinearityChange vs. Temperature

|'NL200/'T| 0.0002 %/C

VOUT 100 mVNonlinearity

NL100 0.0027 0.2 % -100 mV < VIN+ < 100mV 6

Maximum InputVoltage beoreVOUT Clipping

|VIN+|MAX 308.0 mV 9

Input Supply Current IDD1 10.86 16.0 mA VIN+ = 400 mV 10 7

Output Supply Current IDD2 11.56 20.0 mA VIN+ = -400 mV 8

Input Current IIN+ -5 -0.5 PA 11 9

Magnitude o InputBias Current vs.Temperature coecient

|'IIN/'T| 0.45 nA/C

Output Low Voltage VOL 1.29 V 10

Output High Voltage VOH 3.80 V

Output Common-ModeVoltage

VOCM 2.2 2.545 2.8 V

Output Short-CircuitCurrent

|IOSC| 18.6 mA 11

Equivalent Input Imped-ance

RIN 500 k:

VOUT Output Resistance ROUT 15 :

Input DC Common-ModeRejection Ratio

CMRRIN 76 dB 12

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AC Electrical Specifcations

Unless otherwise noted, all typicals and fgures are at the nominal operating conditions o VIN+ = 0, VIN- = 0 V, VDD1 =VDD2 = 5 V and TA = 25C; all Min./Max. specifcations are within the Recommended Operating Conditions.


VOUT Bandwidth

(-3 dB) sine wave.

BW 50 100 kHz VIN+ = 200mVpk-pk 12,13

VOUT Noise NOUT 6 mVRMS VIN+ = 0.0 V 13

VIN to VOUT SignalDelay (50 10%)

tPD10 2.03 3.3 Ps Measured at output oMC34081on Figure 15.

4,15


tPD50 3.47 5.6 Ps VIN+ = 0 mV to 150mV step.


tPD90 4.99 9.9 Ps

VOUT Rise/ Fall Time(10 90%)

tR/F 2.96 6.6 Ps

Common Mode

Transient Immunity

CMTI 10.0 15.0 kV/Ps VCM = 1 kV, TA = 25C 16 14

Power SupplyRejection

PSR 170 mVRMS With recommendedapplication circuit.

15

Package Characteristics


Input-OutputMomentary WithstandVoltage

VISO 3750 VRMS RH < 50%,t = 1 min. TA = 25C

16,17

Resistance(Input-Output)

RI-O >109 : VI-O = 500 VDC 18

Capacitance(Input-Output)

CI-O 1.2 pF = 1 MHz 18

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Notes:General Note: Typical values represent the mean value o allcharacterization units at the nominal operating conditions. Typical dritspecifcations are determined by calculating the rate o change o thespecifed parameter versus the drit parameter (at nominal operatingconditions) or each characterization unit, and then averaging theindividual unit rates. The corresponding drit fgures are normalized tothe nominal operating conditions and show how much drit occurs as

the par-ticular drit parameter is varied rom its nominal value, with allother parameters held at their nominal operating values. Note that thetypical drit specifcations in the tables below may dier rom the slopeso the mean curves shown in the corresponding fgures.1. Avago Technologies recommends operation with VIN- = 0 V (tied to

GND1). Limiting VIN+ to 100 mV will improve DC nonlinearity andnonlinearity drit. I VIN- is brought above VDD1 2 V, an internal testmode may be activated. This test mode is or testing LED couplingand is not intended or customer use.

2. This is the Absolute Value o Input Oset Change vs. Temperature.3. Gain is defned as the slope o the best-ft line o dierential output

voltage (VOUT+VOUT-) vs. dierential input voltage (VIN+VIN-) overthe specifed input range.

4. This is the Absolute Value o Gain Change vs. Temperature in PPMlevel.

5. Nonlinearity is defned as hal o the peak-to-peak output deviation

rom the best-ft gain line, expressed as a percentage o the ull-scaledierential output voltage.

6. NL100 is the nonlinearity specifed over an input voltage range o100 mV.

7. The input supply current decreases as the dierential input voltage(VIN+VIN-) decreases.

8. The maximum specifed output supply current occurs when thedierential input voltage (VIN+VIN-) = -200 mV, the maximumrecommended operating input voltage. However, the output su pplycurrent will continue to rise or dierential input voltages up toapproximately -300 mV, beyond which the output supply currentremains constant.

9. Because o the switched-capacitor nature o the input sigma-deltaconverter, time-averaged values are shown.

10. When the dierential input signal exceeds approximately 308 mV,the outputs will limit at the typical values shown.

11. Shor t circuit current is the amount o output current generated wheneither output is shorted to VDD2 or ground.

12. CMRR is defned as the ratio o the dierential signal gain (signalapplied dierentially between pins 2 and 3) to the common-modegain (input pins tied together and the signal applied to both inputsat the same time), expressed in dB.

13. Output noise comes rom two primary sources: chopper noise andsigma-delta quantization noise. Chopper noise results rom chopperstabilization o the output op-amps. It occurs at a specifc requency

(typically 400 kHz at room temperature), and is not attenuated bythe internal output flter. A flter circuit can be easily added to theexternal post-amplifer to reduce the total RMS output noise. Theinternal output flter does eliminate most, but not all, o the sigma-delta quantization noise. The magnitude o the output quantizationnoise is very small at lower requencies (below 10kHz) and increaseswith increasing requency.

14. CMTI (Common Mode Transient Immunity or CMR, Common ModeRejection) is tested by applying an exponentially rising/allingvoltage step on pin 4 (GND1) with respect to pin 5 (GND2). Therise time o the test waveorm is set to approximately 50 ns. Theamplitude o the step is adjusted until the dierential output ( VOUT+VOUT-) exhibits more than a 200 mV deviation rom the averageoutput voltage or more than 1Ps. The ACPL-782T will continue tounction i more than 10 kV/Ps common mode slopes are applied, aslong as the breakdown voltage limitations are observed.

15. Datasheet value is the dierential amplitude o the transient at theoutput o the ACPL-782T when a 1 Vpk-pk, 1 MHz square wave with 40ns rise and all times is applied to both VDD1 and VDD2.

16. In accordance with UL 1577, each optocoupler is proo tested byapplying an insulation test voltage 4500 VRMS or 1 second (leakagedetection current limit, II-O 5 PA). This test is perormed beore the100% production test or partial discharge (method b) shown in IEC60747-5-5/DIN EN 60747-5-2 Insulation Characteristic Table.

17. The Input-Output Momentary Withstand Voltage is a dielectricvoltage rating that should not be interpreted as an input-outputcontinuous voltage rating. For the continuous voltage rat ing reers tothe IEC 60747-5-5/DIN EN 60747-5-2 insulation characteristics tableand your equipment level saety specifcation.

18. This is a two-terminal measurement: pins 14 are shorted togetherand pins 58 are shorted together.

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TA - TEMPERATURE - C

0.6

0.5

0.3

-25

0.8

35 950.2

0.7

-55 125

0.4

5 65

VOS-INPUTOFFSETVOLTAGE-mV

VDD - SUPPLY VOLTAGE - V

0.37

0.36

0.39

4.75 5.00.33

vs. VDD1

4.5 5.55.25

vs. VDD2

0.34

0.38

0.35

VOS-INPUTOFFSETVOLTAGE-mV

G-GAIN-V/V


8.025

8.02

8.015

-35

8.035

25 858.01

8.03

-55 1255 45 105-15 65

Figure 3. Input Oset Voltage vs. Supply.

Figure 4. Gain vs. Temperature.

Figure 1. Input Oset Voltage Test Circuit.

Figure 2. Input Oset Voltage vs. Temperature.

0.1PF

VDD2

VOUT

8

7

6

1

3

ACPL-782T

5

2

4

0.1PF

10 K

10 K

VDD1 +15 V

0.1PF

0.1PF

-15 V

+

-AD624CD

GAIN = 100

0.47PF

0.47PF

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G-GAIN-V/V


8.028

8.032

4.75 5.08.024

4.5 5.55.25

8.03

8.026 vs. VDD1

vs. VDD2

N

L-NONLINEARITY-%


0.02

0.015

0.005

-25

0.03

35 950

0.025

-55 125

0.01

5 65

NL-NONLINEARITY

-%


0.005

4.75 5.00.002

4.5 5.55.25

0.004

0.003

vs. VDD1

vs. VDD2

VO-OUTPUTVOLTAGE-V

VIN - INPUT VOLTAGE - V

2.6

1.8

-0.3

4.2

-0.1 0.1 0.31.0

3.4

-0.5 0.5

VOP

VOR

Figure 5. Gain and Nonlinearity Test Circuit.

0.1PF

VDD2

8

7

6

1

3

ACPL-782T

5

2

4

0.01PF

10 K

10 K

+15 V

0.1PF

0.1PF

-15 V

+

- AD624CD

GAIN = 4

0.47

PF

0.47

PF

VDD1

13.2

404VIN

VOUT

+15 V

0.1PF

0.1PF

-15 V

+

- AD624CD

GAIN = 10

10 K

0.47

PF

0.1PF

Figure 6. Gain vs. Supply. Figure 7. Nonlinearity vs. Temperature.

Figure 8. Nonlinearity vs. Supply. Figure 9. Output Voltage vs. Input Voltage.

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IDD-SUPPLYCURRENT-mA


7

-0.3

13

-0.1 0.1 0.34

10

-0.5 0.5

IDD1IDD2

IIN-INPUTCURRENT-PA


-3

-0.4

0

-0.2 0.2 0.4-5

-1

-0.6 0.6

-2

-4

0

GAIN-dB

FREQUENCY (Hz)

-2

1

-4

0

10 100000

-1

-3

1000100 10000

PHASE-DEGREES

FREQUENCY (Hz)

-100

50

-300

0

10 100000

-50

-150

1000

-200

-250

100 10000

PD

-PROPAGATION

DELAY-PS


3.1

-25

5.5

5 65 951.5

4.7

-55 125

3.9

2.3

35

Tpd 10Tpd 50Tpd 90Trise

Figure 12. Gain vs. Frequency. Figure 13. Phase vs. Frequency.

Figure 14. Propagation Delay vs. Temperature.

Figure 10. Supply Current vs. Input Voltage. Figure 11. Input Current vs. Input Voltage.

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Figure 15. Propagation Delay Test Circuits.

Figure 16. CMTI Test Circuits.

0.1PF

VDD2

VOUT

8

7

6

1

3

ACPL-782T

5

2

4

2 K

2 K

+15 V

0.1PF

0.1PF

-15 V

-

+ MC34081

0.1PF

10 K

10 K

0.01PF

VDD1

VIN

VIN IMPEDANCE LESS THAN 10W.

0.1PF

VDD2

VOUT

8

7

6

1

3

ACPL-782T

5

2

4

2 K

2 K

78L05

+15 V

0.1PF

0.1PF

-15 V

-

+ MC34081

150pF

IN OUT

0.1PF

0.1PF

9 V

PULSE GEN.

VCM

+ -

10 K

10 K

150 pF

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Application Inormation

Power Supplies and Bypassing

The recommended supply connections are shown inFigure 17. A oating power supply (which in manyapplications could be the same supply that is used to drive

the high-side power transistor) is regulated to 5 V using asimple zener diode (D1); the value o resistor R4 shouldbe chosen to supply sucient current rom the existingoating supply. The voltage rom the current sensingresistor (Rsense) is applied to the input o the ACPL-782Tthrough an RC anti-aliasing flter (R2 and C2). Although theapplication circuit is relatively simple, a ew recommenda-tions should be ollowed to ensure optimal perormance.

The power supply or the ACPL -782T is most oten obtainedrom the same supply used to power the power transis-tor gate drive circuit. I a dedicated supply is required, inmany cases it is possible to add an additional winding on

an existing transormer. Otherwise, some sort o simpleisolated supply can be used, such as a line powered trans-ormer or a high-requency DC-DC converter.

An inexpensive 78L05 three-terminal regulator can alsobe used to reduce the oating supply voltage to 5 V. Tohelp attenuate high-requency power supply noise or

ripple, a resistor or inductor can be used in series with theinput o the regulator to orm a low-pass flter with theregulators input bypass capacitor.

As shown in Figure 18, 0.1 PF bypass capacitors (C1, C2)should be located as close as possible to the pins o theACPL-782T. The bypass capacitors are required becauseo the high-speed digital nature o the signals inside theACPL-782T. A 0.01F bypass capacitor (C2) is also rec-ommended at the input due to the switched-capacitornature o the input circuit. The input bypass capacitoralso orms part o the anti-aliasing flter, which is recom-mended to prevent high-requency noise rom aliasing

down to lower requencies and interering with theinput signal. The input flter also perorms an importantreliability unctionit reduces transient spikes rom ESDevents owing through the current sensing resistor.

ACPL-782T

C10.1 F

R2

39 :

GATE DRIVECIRCUIT

FLOATINGPOWERSUPPLY* * *

HV+

* * *

HV-

* * *

-+

RSENSE

MOTOR

C20.01 F

D15.1 V

-

+

R1

Figure 17. Recommended Supply and Sense Resistor Connections.

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0.1 F

+5 V

VOUT

8

7

6

1

3

U2

5

2

4

R1

2.00 K

+15 VC8

0.1 F

0.1 F

-15 V

-

+ MC34081

R3

10.0 K

ACPL-782T

C4

R410.0 K

C6150 pF

U3

U178L05

IN OUT

C1 C2

0.01F

R5

68

GATE DRIVECIRCUIT

POSITIVEFLOATINGSUPPLY

HV+

* * *

HV-

-+

RSENSE

MOTOR

C5150 pF

0.1F

0.1F

C3

C7

R2

2.00 K

* * *

* * *

Figure 18. Recommended Application Circuit.

Figure 19. Example Printed Circuit Board Layout.

PC Board Layout

The design o the printed circuit board (PCB) should ollowgood layout practices, such as keeping bypass capacitorsclose to the supply pins, keeping output signals away rominput signals, the use o ground and power planes, etc. Inaddition, the layout o the PCB can also aect the isolation

transient immunity (CMTI) o the ACPL-782T, due primarilyto stray capacitive coupling between the input and theoutput circuits. To obtain optimal CMTI perormance, thelayout o the PC board should minimize any stray couplingby maintaining the maximum possible distance betweenthe input and output sides o the circuit and ensuring thatany ground or power plane on the PC board does not passdirectly below or extend much wider than the body o theACPL-782T.

C3

C2 C4R5

TO RSENSE+TO RSENSE-

TO VDD1TO VDD2VOUT+VOUT-

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Current Sensing Resistors

The current sensing resistor should have low resistance (tominimize power dissipation), low inductance (to minimizedi/dt induced voltage spikes which could adverselyaect operation), and reasonable tolerance (to maintainoverall circuit accuracy). Choosing a particular value or

the resistor is usually a compromise between minimiz-ing power dissipation and maximizing accuracy. Smallersense resistance decreases power dissipation, while largersense resistance can improve circuit accuracy by utilizingthe ull input range o the ACPL -782T.

The frst step in selecting a sense resistor is determininghow much current the resistor will be sensing. The graph inFigure 20 shows the RMS current in each phase o a three-phase induction motor as a unction o average motoroutput power (in horsepower, hp) and motor drive supplyvoltage. The maximum value o the sense resistor is deter-mined by the current being measured and the maximum

recommended input voltage o the isolation amplifer. Themaximum sense resistance can be calculated by takingthe maximum recommended input voltage and dividingby the peak current that the sense resistor should seeduring normal operation. For example, i a motor will havea maximum RMS current o 10 A and can experience upto 50% overloads during normal operation, then the peakcurrent is 21.1 A (=10 x 1.414 x 1.5). Assuming a maximuminput voltage o 200 mV, the maximum value o sense re-sistance in this case would be about 10 m:.

The maximum average power dissipation in the senseresistor can also be easily calculated by multiplying the

sense resistance times the square o the maximum RMScurrent, which is about 1 W in the previous example. I thepower dissipation in the sense resistor is too high, the re-sistance can be decreased below the maximum value todecrease power dissipation. The minimum value o thesense resistor is limited by precision and accuracy require-

Figure 20. Motor Output Horsepower vs. Motor Phase Current and Supply

Voltage.

ments o the design. As the resistance value is reduced,the output voltage across the resistor is also reduced,which means that the oset and noise, which are fxed,become a larger percentage o the signal amplitude. Theselected value o the sense resistor will all somewhere

between the minimum and maximum values, dependingon the particular requirements o a specifc design.

When sensing currents large enough to cause signifcantheating o the sense resistor, the temperature coecient(tempco) o the resistor can introduce nonlinearity due tothe signal dependent temperature rise o the resistor. Theeect increases as the resistor-to-ambient thermal resis-tance increases. This eect can be minimized by reducingthe thermal resistance o the current sensing resistor orby using a resistor with a lower tempco. Lowering thethermal resistance can be accomplished by reposition-ing the current sensing resistor on the PC board, by using

larger PC board traces to carry away more heat, or byusing a heat sink.

For a two-terminal current sensing resistor, as the value oresistance decreases, the resistance o the leads become asignifcant percentage o the total resistance. This has twoprimary eects on resistor accuracy. First, the eectiveresistance o the sense resistor can become dependenton actors such as how long the leads are, how they arebent, how ar they are inserted into the board, and how arsolder wicks up the leads during assembly (these issueswill be discussed in more detail shortly). Second, the leadsare typically made rom a material, such as copper, which

has a much higher tempco than the material rom whichthe resistive element itsel is made, resulting in a highertempco overall.

Both o these eects are eliminated when a our-terminalcurrent sensing resistor is used. A our- terminal resistorhas two additional terminals that are Kelvin-connecteddirectly across the resistive element itsel; these twoterminals are used to monitor the voltage across theresistive element while the other two terminals are usedto carry the load current. Because o the Kelvin connec-tion, any voltage drops across the leads carrying the loadcurrent should have no impact on the measured voltage.

When laying out a PC board or the current sensing resistors,a couple o points should be kept in mind. The Kelvin con-nections to the resistor should be brought together underthe body o the resistor and then run very close to eachother to the input o the ACPL-782T; this minimizes theloop area o the connection and reduces the possibility ostray magnetic felds rom interering with the measuredsignal. I the sense resistor is not located on the same PCboard as the ACPL-782T circuit, a tightly twisted pair owires can accomplish the same thing.

MOTORPHASE CURRENT - A (rms)

15

5

40

10 25 300

35

0 35

25

10

20

440 V380 V220 V120 V

30

20

5

15

MOTOROUTPUTPOW

ER-HORSEPOWER

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Also, multiple layers o the PC board can be used toincrease current carrying capacity. Numerous plated-through vias should surround each non-Kelvin terminal othe sense resistor to help distribute the current betweenthe layers o the PC board. The PC board should use 2 or4 oz. copper or the layers, resulting in a current carrying

capacity in excess o 20 A.Note: Please reer to Avago Technologies Application Note 1078 oradditional inormation on using Isolation Amplifers.

Sense Resistor Connections

The recommended method or connecting the ACPL-782Tto the current sensing resistor is shown in Figure 18. VIN+(pin 2 o the APCL-782T) is connected to the positiveterminal o the sense resistor, while VIN- (pin 3) is shortedto GND1 (pin 4), with the power-supply return path unc-tioning as the sense line to the negative terminal o thecurrent sense resistor. This allows a single pair o wiresor PC board traces to connect the ACPL-782T circuit to

the sense resistor. By reerencing the input circuit tothe negative side o the sense resistor, any load currentinduced noise transients on the resistor are seen as acommon-mode signal and will not interere with the cur-rent-sense signal. This is important because the large loadcurrents owing through the motor drive, along with theparasitic inductances inherent in the wiring o the circuit,can generate both noise spikes and osets that are rela-tively large compared to the small voltages that are beingmeasured across the current sensing resistor.

I the same power supply is used both or the gatedrive circuit and or the current sensing circuit, it is

very important that the connection rom GND1 o theACPL-782T to the sense resistor be the only return path or

supply current to the gate drive power supply in order toeliminate potential ground loop problems. The only directconnection between the ACPL-782T circuit and the gatedrive circuit should be the positive power supply line.

Output Side

The op-amp used in the external post-amplifer circuitshould be o suciently high precision so that it does notcontribute a signifcant amount o oset or oset dritrelative to the contribution rom the isolation amplifer.Generally, op-amps with bipolar input stages exhibitbetter oset perormance than op-amps with JFET orMOSFET input stages.

In addition, the op-amp should also have enoughbandwidth and slew rate so that it does not adverselyaect the response speed o the overall circuit. The post-amplifer circuit includes a pair o capacitors (C5 and C6)that orm a single-pole low-pass flter; these capacitors

allow the bandwidth o the post-amp to be adjustedindependently o the gain and are useul or reducingthe output noise rom the isolation amplifer. Manydierent op-amps could be used in the circuit, including:

TL032A, TL052A, and TLC277 (Texas Instruments), LF412A(National Semiconductor).

The gain-setting resistors in the post-amp should have atolerance o 1% or better to ensure adequate CMRR andadequate gain tolerance or the overall circuit. Resistornetworks can be used that have much better ratiotolerances than can be achieved using discrete resistors.A resistor network also reduces the total number ocomponents or the circuit as well as the required boardspace.

Figure 21. Recommended circuit or voltage sensing application.

Line 1

1

2

3

4

8

7

6

5

ACPL-782T

+5 V

+15 V

0.01PF

0.1PF0.1PF

0.1PF

10.0 k:150 pF

2.0 k:

2.00 k:

-15 V

TL032A+

-

VOUT

0.1PF

+ SUPPLY

150 pF

78L05

IN OUT0.1PF

Line 2

6

5

8

4

7

10.0 k:

39:

+5 V

Ra

Rb

Note for the Voltage Divider:V (Line) x [ Rb / (Ra+Rb) ]

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Voltage sensing or DC rail measurement

ACPL-782T is a suitable device to measure the DC railvoltage over dierent potentials. In a DC rail voltagesensing application, the Line1 and Line2 in Figure 21 arethe DC lines to be measured.

Dividing ratio error due to the tolerances o the resistorsFrom a dierential calculation, the error in the voltagedivider o Ra and Rb is expressed as

'A/A = Ra/(Ra + Rb) * ('Rb/Rb 'Ra/Ra) (1)

Where A is the ratio o the resistor divider consisting o Raand Rb.

Since the errors o the resistors, 'Rb/Rb and 'Ra/Ra areindependent to each other, we need to take absolutevalues in equation (1) to know the maximum possiblegain error o the divider and it gives

'A/A = Ra/(Ra + Rb) * ( |'Rb/Rb| + |'Ra/Ra|) (2)

Figure 22 is the plot o the equation (2) when the resistorshave 1% tolerance expressing the relationship betweenthe ratio o Ra to (Ra+Rb) and the possible maximum erroro the dividing ratio.

Dividing error when 1% resistors are used(%)

0

0.5

1

1.5

2

0.5 0.6 0.7 0.8 0.9 1.0

Ra/(Ra+Rb)

Divid

erError(%)

Figure 22: Divider Error % Vs Resistors Divider

Note on the thermistor and the RL:Vdd x [RL/(Rth + RL)] x [ R3/(R2 + R3)] > R1

Rth: Resistance o thermistorRL: Linearizing resistor value = R1//(R2+R3)

1

2

3

4

8

7

6

5

ACPL-782T

+5 V

+15 V

1PF

0.1PF

0.1PF

0.1PF

10.0 k:150 pF

2.0 k:

2.0

-15 V

TL032A+

-

VOUT

0.1PF

+ SUPPLY

150 pF

78L05

IN OUT

0.1PF

6

5

8

4

7

10.0 k:

39:

+5 V

R1

Semitec

EC2F103A2-40113

ThermistorIGBT attaching type

TH

RL =R1//(R2+R3)

R3

R2 k:

Figure 23. Recommended circuit or temperature sensing application.

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For product information and a complete list ofdistributors, please go to our web site: www.avagotech.com

Avago, Avago Technologies, the A logo and R2Coupler are trademarks ofAvago Technologies in the UnitedStates and other countries.

Data subject to change. Copyright 2005-2011 Avago Technologies. All rights reserved.

AV02-1565EN - March 23, 2011

Isolated Temperature Sensing using Thermistor

Thermistor is widely used to measure temperatures inmost systems application. A galvanic isolation betweenthe potential o the Thermistor and that o the analog-to-digital is oten required when they are mounted inlocations such as high voltage potential, electrically noisy

environments, poorly grounded environments, wherelack o isolation causes either saety or EMI issues.

RL = R1//(R2+R3)=R1(R2+R3)/(R1+R2+R3)

R2 and R3 divides the voltage across RL so that the voltageed into ACPL-782T does not exceed +200 mV. The highimpedance characteristic o the input terminals o ACPL-782T helps in determining those resistors value since onecan select relatively high resistance o R2 and R3 and R1can be determined easily.

I R2+R3 >> R1, RL ~ R1Dividing ratio ~ R3/(R2+R3)

As can be seen rom the circuit, one might eliminate R1and RL~(R2+R3) in this case.

An application example with a Thermistor designed ormeasuring IGBTs surace temperatures is shown in Figure23. Where TH is the thermistor and the RL is a resistor orlinearization. Suitable RL value is determined rom the

Thermistor characteristic and the temperature range tomeasure. Please note that the RL value is the compoundvalue o R1, R2 and R3.

acpl-782t

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