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1. Digital current sensor overview, 2012-02


Isolation Products Division

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Digital Current Sensor Overview

Feb 2012

Page 1

Avago Technologies Confidential

Isolation Products Division

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Digital Current Sensors – The Technology
Input Signal Processing Optically Transparent Dielectric Output Signal Processing

Voltage Regulator

Clock Generator

Packaged products
Voltage Regulator LED Drive Circuit

Input

Σ-Δ Modulator

Encoder

Detector Circuit

Decoder and D/A

MCLK MDAT

The Isolation Amplifier/Σ-Δ modulator converts the analog input signal into a high-speed serial bit stream; the time average of the bit stream is directly proportional to the input signal.
This stream of digital data is encoded and optically transmitted to the detector circuit. The detected signal is decoded and converted back into an clock and digital data.
Page 2 Avago Technologies Confidential

Simplified block diagram

Isolation Products Division

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Overview of Isolated Sigma-Delta Modulators
Part Number ACPL-C797/7970 ACPL-796J HCPL-7860/786J HCPL-7560 HCPL-0872 Descriptions ?-? Mod 16-bit, ext clk, –40 to +105°C ?-? Mod 16-bit, ext clk, –40 to +105°C Isolated ?-? Modulator 12 bits res. Isolated ?-? Modulator 8 bits res. Digital Filter
VDD1 VIN+ VIN– GND1 NC NC VDD1 GND1 1 2 3 4 5 6 7 8

Key Features Accurate internal clock frequency Using external clock for synchronization High resolution, shorter signal delay Digital output direct connected to MCU

ASIC/ DSP/ FPGA

?-? ADC CLK DET.

DAT CLK IN

16 15 14 13 12 11 10 9

GND2 NC VDD2 CLKIN NC DATOUT NC GND2

ASIC/ DSP/ FPGA

ACPL-C797/7970 HCPL-7860/7560

ACPL-796J

Page 3

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Isolation Products Division

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Analog Input and Modulator Data
?Input signal information is contained in the modulator output data stream, represented by the density of ones and zeros.
Analog Input Voltage Input Full-Scale Range 640 mV +Full-Scale +320 mV +Recommended +200 mV Input Range Zero 0 mV –Recommended –200 mV Input Range –Full-Scale –320 mV Density ADC Code (16-bit of 1s unsigned decimation)
100% 65,535 81.25% 53,248

50% 32,768 18.75% 12,288
0% 0

Core of the A-D conversion: Sigma-Delta modulation.
MODULATOR OUTPUT +FS (ANALOG INPUT)

ACPL-796J Data Sheet.

0 V (ANALOG INPUT)
–FS (ANALOG INPUT) ANALOG INPUT TIME

Page 4

Avago Technologies Confidential

Isolation Products Division

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Application Example – Current/Voltage Sense in a 3-Phase Motor Inverter
ACPL-796J S T
+ –

Voltage Sense

Voltage Detection

+ –

Brake ACPL-796J

ACPL-796J

ASIC/MCU

3 Isolation Amplifiers are used for 3 phase current measurement; 1 Isolation Amplifier is used for DC link voltage monitoring.
Page 5 Avago Technologies Confidential

+ –

R

Current Sense

M

Isolation Products Division

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Isolation Voltage and Common Mode Noise
3 Phase Voltage applied to Motor

The common mode voltage of the current sensor follows the phase voltages applied to the three phase motor during rotation ? This voltage can be several hundred volts and needs to be isolated from the low voltage circuits of the motion controller Isolation Needed
Current Sense
VCC +-

GND Voltage

+
VCC

-

M
+
+-

The electrical and magnetic environment at the Motor terminals is also very noisy and has high EMI and Switching noise due to large currents and voltages need for Motor Torque. Inductance and Back EMF during IGBT switching also create fast transients that will affect sensitive low voltage electronics.

Page 6

-

High Common Mode Rejection Needed
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Isolation Products Division

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HCPL-7860/786J Isolated Modulator for Current Sensing Application
Benefit
?

Description

Standard industry package suitable for high volume ? Advanced Sigma-Delta (S-D) A/D production processes digital output converter ? Not affected by external magnetic fields; and does ? 12-bit linearity not exhibit residual magnetization effects that ? High CMR (15KV/ms@VCM=1kV) can affect offset. ? ± 200 mV Input Range with Single 5 V Supply ? Direct interface with MCU/DSP ? Wide operating temperature range: –40°C to 85°C ? Allows system calibration ? 0.14% maximum integral nonlinearity ? Single supply solution ? 10mV/°C input offset voltage vs. temperature ? 1% absolute reference voltage matching Applications ? Compact, auto-insertable 8-pin DIP package ? Motor Phase and Rail Current Sensing ? Safety approval: UL, CSA, IEC/EN/DIN EN 60747-5-2 ? Data Acquisition Systems ? Industrial Process Control ? Inverter Current Sensing 1 8 ? General Purpose Current Sensing

Ordering Information
Device Package Option HCPL-7860 DIP-8 HCPL-7860#300 DIP-8 Gull Wing HCPL-7860#500 DIP-8 Tape & Reel HCPL-786J SO-16 HCPL-786J#500 SO-16 Tape & Reel xxxE – Lead-Free Option
Page 7

2 Input Current 3

SIGMADE LTA MOD./ E NCODE

7 DE CODE 6

HCPL-0872
or Digital Filter

MCU or DSP

4

5

HCPL-7860

Avago Technologies Confidential

Isolation Products Division

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HCPL-7560 Isolated Modulator for Current Sensing Application
Benefit
?

Description

? Advanced Sigma-Delta (S-D) A/D Standard industry package suitable for high volume digital output converter production processes ? Not affected by external magnetic fields; and does ? 8-bit linearity not exhibit residual magnetization effects that ? High CMR (15KV/ms@VCM=1kV) ? ± 200 mV Input Range with Single 5 V Supply can affect offset. ? Wide operating temperature range: –40°C to 85°C ? Direct interface with MCU/DSP ? 0.8% maximum integral nonlinearity ? Allowed system calibration ? 35mV/°C input offset voltage vs. temperature ? Single supply solution ? ±5% absolute reference voltage matching Applications ? Compact, auto-insertable 8-pin DIP package ? Motor Phase and Rail Current Sensing ? Safety approval: UL, CSA, IEC/EN/DIN EN 60747-5-2 ? Data Acquisition Systems ? Industrial Process Control ? Inverter Current Sensing 1 8 ? General Purpose Current Sensing
2 SIGMADE LTA MOD./ E NCODE 7 DE CODE 6

Ordering Information
Device Package Option HCPL-7560 DIP-8 HCPL-7560-060 DIP-8 IEC HCPL-7560-300 DIP-8 Gull Wing HCPL-7560-500 DIP-8 Tape & Reel HCPL-7560-360 DIP-8 IEC and Gull Wing HCPL-7560-560 DIP-8 IEC and Tape & Reel xxxE – Lead-Free Option Page 8

Input Current 3

HCPL-0872
or Digital Filter

MCU or DSP

4

5

HCPL-7560

Avago Technologies Confidential

Isolation Products Division

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HCPL-0872 Digital Interface IC for Isolated Modulator for Current Sensing Application
Benefit
?

Description

Standard industry package suitable for high volume ? Interface between HCPL-7860/786J/7560 production processes and MCU/DSP ? Direct interface with MCU/DSP ? 200 ns (typ)Conversion Time (Pre-Trigger Mode 2) ? Allowed system calibration ? 5 Conversion Modes for Resolution/Speed Trade-Off ? Single supply solution ? 3 Pre-Trigger Modes ? Not affected by external magnetic fields; and does ? Fast 3 ms Over-Range Detection not exhibit residual magnetization effects that ? Offset Calibration can affect offset. ? Wide operating temperature range: –40°C to 85°C ? Adjustable Threshold Detection Applications ? ? and Microwire Compatible) ? Serial I/O (SPI , QSPI ? Motor Phase and Rail Current Sensing Data Acquisition Systems ? Industrial Process Control ? Inverter Current Sensing ? General Purpose Current Sensing and Monitoring
?
HCPL-7560
VDD1
Input Current

VDD2 MCLK MDAT GND2

1 2 3 4 5 6

CCLK

VDD

16 15 14 13 12 11 10 9

VIN+ VINGND1

CONFIG CLAT INTERCHAN FACE CON VE RSION CDAT SCLK INTE RFACE

MCLK1 MDAT1 MCLK2

SDAT

CH1

MCU or DSP

CS THR1

Ordering Information

VDD1
Input Current

VDD2 MCLK MDAT GND2

Device Package Option HCPL-0872 SO-16 HCPL-0872-500 SO-16 Tape & Reel xxxE – Lead-Free Option

7 8

VIN+ VINGND1

THRE S MDAT2 CH2 HOLD OVR1 DE TE CT & RE SE T

GND

RESET

HCPL-0872

HCPL-7560

Page 9

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Isolation Products Division

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Features Benefit ? Advanced Sigma-Delta A/D conversion technology ? -40°C to +105°C extended industrial operating temperature range ? 12-bit Effective Resolution ? SSO-8 surface mount package saves 30% PCB vs. ? High CMR (15KV/?s@VCM=1kV) DIP-8 ? ±200 mV Input Range with Single 5 V Supply ? 3 to 5.5V supply voltage directly interface with ? Wide operating temperature range: –40°C to 105°C MCU/DSP ?2.2?V/°C input offset voltage temperature drift ? ?1% gain error for better system accuracy ?Compact, auto-insertable 8-pin DIP package ? ?10% internal clock frequency ? Safety approval: UL, CSA, IEC/EN/DIN EN 60747-5-2 ? 5kVrms/1min isolation voltage per UL1577 ? 1230Vpk working voltage per IEC ? 8mm creepage and clearance
1 8

ACPL-C797 Isolated ?-? Modulator with Operating Temperature up to 105°C

Applications ? Motor Phase and Rail Current Sensing ? Data Acquisition Systems ? Industrial Process Control ? Inverter Current Sensing ? General Purpose Current Sensing
Page 10

2 Input Current 3

SIGMADE LTA MOD./ E NCODE

7 DE CODE 6

HCPL-0872
or Digital Filter

MCU or DSP

4

ACPL-C797 HCPL-7860

5

Avago Technologies Confidential

Isolation Products Division

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ACPL-C797 – Better Accuracy and Extended Operating Temperature Range in Smaller Package
Operating temperature TA (°C) Output clock frequency fCLK (MHz) Internal reference voltage VREF (mV) Reference voltage tolerance ?1% min/max ?4% min/max (Gain error) Input Offset voltage VOS (mV) 0.5 typ, -1 min, 2 max -3 min, 0 typ, 3 max Offset drift (?V/°C) Signal to noise ratio SNR (dB) Signal to noise+dist. SNDR (dB) Resolution, ENOB (bits) Package Safety Approval 2.2 typ, 10 max 78 typ, 74 min 75 typ, 65 min 12 typ, 10.5 min SSO-8 SMD 2 typ, 10 max 73 typ, 62 min 66 typ 11 typ DIP-8 with surface mount option UL 5kVrms, CSA and UL 3750Vrms, CSA and IEC 891Vpk IEC 1230Vpk

ACPL-C797 (NEW) HCPL-7860 -40 to +105 -40 to +85 10 typ, ?10% min/max 8.2 min, 10 typ, 13.2 max ?320 typ ?320 typ

Note Improved op. temp. range Reduced data conversion loss

Better gain accuracy Improved offset voltage Improved SNR Improved SNDR Better resolution 8 mm clearance and creepage Improved insulation capability

Blue – Improved specifications.
Page 11 Avago Technologies Confidential

Isolation Products Division

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Benefits of Stretched SO-8 over DIP-8 package
Parameter ACPL-C797 HCPL-7860 Note C797 saves 30% PCB space Stretched SO-8 (SSO-8) 0.5 mm 8 mm 8 mm DIP-8 0.5 mm 8 mm 7.4 mm

Package

Distance Through Insulation, DTI (min) Creepage (min)
Clearance (min)

Working Insulation Volt. VIORM
Isolation Voltage Viso

1230 Vpeak
5000 Vrms/1min

891 Vpeak
3750 Vrms/1min

Meets medical application requirement SSO-8 meets 8 mm creepage and clearance requirements Safety approval per IEC/EN/DIN EN 60747-5-2 Safety approval per UL 1577

Benefits: ? Saves 30% PCB space (vs. DIP-8 gullwing surface mount option) ? Meets regulatory requirements of 8 mm creepage and clearance ? Upgrade to 1230 Vpeak working insulation voltage and 5kVrms/1min isolation voltage
Page 12 Avago Technologies Confidential

Isolation Products Division

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ACPL-796J Isolated Sigma-Delta Modulator, External Clock - Functional block diagram
Market Release: Nov 2008
VDD1 VIN+ VIN– LED DRIVER SHIELD VDD2 ?-? MODULATOR/ ENCODER

DECODER

MDAT

BUF

CLOCK DETECTOR SHIELD

LED DRIVER

MCLKIN

VREF GND1

ACPL-796J

GND2

VDD1 1 VIN+ 2 VIN– 3 GND1 4 NC 5 NC 6 VDD1 7 CLK DET. CLK IN ?-? ADC DAT

16 GND2

15 NC
14 VDD2 13 CLKIN 12 NC 11 DATOUT 10 NC

ASIC/ DSP/ FPGA

GND1 8

9 GND2

ACPL-796J
Page 13 Avago Technologies Confidential

Isolation Products Division

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Features
? ? ? ? ? ? ? ? ? ?

ACPL-796J Isolated Sigma-Delta Modulator Using External Clock
External Clock Input: 5 MHz to 20 MHz 74 dB min SNR 12 bits ENOB ?1% max gain error 3.5 ?V/°C max offset drift 3 to 5.5V wide digital side supply range 25 kV/us common-mode rejection at VCM=1000V Wide temperature range, –40oC to 105oC SO-16 package Worldwide safety approval (pending) ?CSA; UL1577 5kV; IEC 1230Vpk
VDD1 VIN+ VIN– GND1 NC NC VDD1 GND1
VDD1 VIN+ VIN– GND1 NC NC VDD1 GND1 VDD1 VIN+ VIN– GND1 NC NC VDD1 GND1 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 ?-? ADC DATA 16 15 14 13 12 11 10 9 16 15 14 13 12 11 10 9 16 15 14 13 12 11 10 9

CLK DET.

CLK IN

ACPL-796J

GND2 NC VDD2 CLKIN NC DATOUT NC GND2
GND2 NC VDD2 CLKIN NC DATOUT NC GND2 GND2 NC VDD2 CLKIN NC DATOUT NC GND2

?-? ADC

DATA

CLK DET.

CLK IN

DSP/ FPGA

Applications
? ? ? ? ? Inverter/Motor Phase and Rail Current sensing Data acquisition systems Industrial process control General purpose current sensing and monitoring Traditional current transducer replacements

ACPL-796J

?-? ADC

DATA

CLK DET.

CLK IN

Options
? 000E, 060E, 500E, 560E
Page 14

ACPL-796J

Avago Technologies Confidential

Isolation Products Division

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ACPL-796J Product Highlights
? New ACPL-796J sigma-delta modulator using external clock in SO-16 package
? Synchronized data conversion (no data stream loss) using clock from controller ? Single clock source from controller synchronize multiple converters ? Auto-insertable surface mount package suitable for automated PCB assembly mass production ? Compact package reduces PCB size compared to traditional solution

? High CMR capability
? provide smoother control – less torque ripple – in their motor control applications

? Advanced 1-bit, 2nd order sigma-delta converter technology
? Provides the precision and stability needed to accurately monitor motor current in high noise motor control environments

? Low offset voltage, low gain error, high linearity
? Provides excellent signal gain accuracy, and stability over time and a range of temperatures

? Meets Worldwide Safety Approvals: UL 1577, CSA and IEC/EN/DIN EN 60747-5-5
? Reinforced insulation capability provides guaranteed galvanic isolation ? Excellent solution for fail-safe designs
Page 15 Avago Technologies Confidential

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ACPL-796J pin-outs vs. AD7401(A) – 100% compatible
? ACPL-796J is pin-to-pin compatible to AD7401:
VDD1 VIN+ VIN– GND1 NC NC VDD1 GND1 1 2 3 4 5 6 7 8 CLK DET. CLK IN ?-? MOD./ ENCODER DATA 16 GND2 15 NC 14 VDD2 13 CLKIN 12 NC 11 DATOUT 10 NC GND2

ACPL-796J

9

Page 16

Avago Technologies Confidential

Isolation Products Division

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ACPL-796J’s capability against Latch-up
? High over voltage input rating
? Esp. important for drives using trench IGBT’s with very high SC current levels which produces high transient voltage on the sensor input pins

? ESD input protection of the inputs with latch up tolerance to over current conditions
? Unlike ESD events, over current related induced voltage over voltages are of much longer duration are not current limited and hence are readily able to destroy parts through latch-up.

? ACPL-796J’s over voltage transient specs
Parameter Symbol Min. –0.5 –2 Supply voltage Steady-State Input Voltage[1] VDD1, VDD2 VIN+, VIN–

Max. 6.5 VDD1 + 0.5

Units V V

Two-Second Transient Input Voltage[2] VIN+, VIN– –6 VDD1 + 0.5 V 1. Absolute maximum DC current on the inputs = 100 mA, no latch-up or device damage occurs. 2. DC voltage of up to –2 V on the inputs does not cause latch-up or damage to the device; tested at typical operating conditions. 3. Transient voltage of 2 seconds up to –6 V on the inputs does not cause latch-up or damage to the device; tested at typical operating conditions.
Page 17 Avago Technologies Confidential

Isolation Products Division

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Evaluation Boards for Isolation Amplifiers

ACPL-796J + HCPL-0872 evaluation kit with on-board clock

ACPL-C797, HCPL-7860/7560 + HCPL-0872 evaluation kit

Page 18

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Isolation Products Division

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796J+FPGA Eval Kit

Page 19

Avago Technologies Confidential


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