NVE Sensor and Isolator News
January 2009
In This Issue

Hot 100 Award

New Current Sensor

Application Corner

Sensor Part Numbering

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Isolator Selector Guide

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<Sensors via Digi-Key>

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Product News

Isolators Named to Hot 100 HOT!

IL500 digital isolators
Award-winning IL500 digital isolators
pack in as many as four channels
and operate as fast as 2 Mbps.
NVE's new IL500-Series digital isolators have been named a Hot 100 Product of 2008 in the latest issue of EDN.

According to EDN, the prestigious annual listing is compiled by its editors and highlights the electronics industry's most innovative and significant products.

Designed to be cost-effective optocoupler replacements, IL500-Series isolators operate at two megabits per second, offer a dc-correct design, and have an external synchronization option on certain models.

Key specifications are:
  • 2 Mbps; 10 ns PWD
  • DC Correct
  • External Clock Option (IL510; IL515)
  • Output Enable (IL510; IL514; IL515)
  • 1, 2, 3, or 4 Channels
  • -40°C to 85°C Temp. Range
  • 2.5 kVrms Isolation (1 min.)
  • UL1577 and IEC 61010-2001 Approved
  • MSOP and SOIC Packages

<More About Award-Winning IL500 Isolators>

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Current Sensor NEW!

The new AAV003-10E is a highly linear, extremely low hysteresis GMR current sensor with an on-chip current strap. A GMR bridge sensor element close to the strap senses the current. The output of the bridge voltage is bipolar and proportional to the current through the strap over a -80 to +80 mA input range.

AAV003-10E Current Sensor
AAV003-10E Current Sensor
Typical sensitivity is a remarkable 1 mV/V with a 12 V supply and no amplification.

The parts come in an ultraminiature 2.5 mm by 2.5 mm 6-pin TDFN package.

AAV003-10E current sensors are targeted at circuit board current sensing for process control and instrumentation. Their sensitivity makes them ideal for 4-20 mA current loop detection.

<More About NVE's New Current Sensors>

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Application Corner
Noncontact Current Measurement
Using Analog Sensors
By Jay Brown
Vice President, Sensors

In addition to the new AAV003-10E covered above, AA- or AAH-Series GMR magnetometers can determine ac or dc current by measuring the magnetic field from a circuit board trace without a direct connection. This method can be used to measure large currents, and the accuracy is generally adequate for overcurrent protection.

The axis of magnetic sensitivity is along the package, so the configuration shown below is often used, with the current-carrying trace on the opposite side of circuit board from the sensor:

Current Sensor Configuration

The magnetic field at the sensor element is approximated as:


Where I is the current in conductor, r is the distance of the sensor from the center of the conductor, and H is the magnetic field at the sensor element in A/m using SI units (1 A/m = 0.0126 Oe in air).

For example, with a SOIC-packaged sensor on a 1.6 mm thick PCB with 3 oz plated copper, r = 2.94 mm. If D1 = D2 = 10 mm, the critical field strength at the sensor for a 10 A overcurrent would be 519 A/m or 6.54 Oe. A circuit can easily be designed with an AA002-2 sensor and a comparator to switch at 6.54 Oe or 10 A.

For more information on current measurement designs, including a detailed circuit for this example, see Application Bulletin No. 
SA-1 (.pdf)
. You can also download the recently updated Current Field Calculator (.xls).

<More Sensor Applications>

Sensor Part Numbering

NVE sensor part numbers have five alphanumeric fields as summarized below:

AA H 004 - 00 E

Base Part
  AA = Analog output magnetometer
  AB = Analog output gradiometer
  AD = Digital switch
  AF = Low-voltage digital switch
  AG = Evaluation kit or PCB
  AK = Digital output gradiometer
  BA = Custom analog sensor
  BD = Custom digital sensor
  DB = Digital signal processing IC
  DC = Voltage regulator
  DD = Analog signal processing IC

GMR Material
  Blank = Standard material
  H = High-sensitivity, high-temp. multilayer
  L = Low hysteresis, high-temp. multilayer
  V = Spin-valve material
Part Subtype
  (meaning depends on Base Part)

Package Type
  00 = MSOP8
  01 = Bare die
  02 = SOIC8
  07 = Non-IC such as eval. kit or PCB
  10 = 2.5 mm x 2.5 mm TDFN6
  11 = 3 mm x 3 mm PLLP6
  12 = 4.9 mm x 6.0 mm TDFN SO8

Part Package
  Blank = Lead (Pb)
  E = RoHS