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NVE Corporation 11409 Valley View Road

Eden Prairie, MN 55344-3617 USA

Telephone: (952) 829-9217

Fax: (952) 829-9189

Internet: www.isoloop.com

Application Notes:

Dynamic Power Consumption

manner by which they transmit data across the isolation barrier. By

detecting the edge transitions of the input logic signal and

converting these to narrow current pulses, a magnetic field is

created around the GMR Wheatstone bridge. Depending on the

direction of the magnetic field, the bridge causes the output

comparator to switch following the input logic signal. Power

consumption is independent of mark-to-space ratio and solely

dependent on frequency. This has obvious advantages over

optocouplers whose power consumption is heavily dependent on

its on-state and frequency.

The maximum power supply current per channel for

Power Supply Decoupling

Both power supplies to these devices should be decoupled with

low ESR 100 nF ceramic capacitors. For data rates in excess of

10MBd, use of ground planes for both GND1 and GND2 is highly

recommended. Capacitors should be located as close as possible to

the device.

Signal Status on Start-up and Shut Down

To minimize power dissipation, the input signals are differentiated

and then latched on the output side of the isolation barrier to

reconstruct the signal. This could result in an ambiguous output

state depending on power up, shutdown and power loss

sequencing. Therefore, the designer should consider the inclusion

of an initialization signal in his start-up circuit. Initialization

consists of toggling the input either high then low or low then

high, depending on the desired state.

Electrostatic Discharge Sensitivity

This product has been tested for electrostatic sensitivity to the

limits stated in the specifications. However, NVE recommends that

all integrated circuits be handled with appropriate care to avoid

damage. Damage caused by inappropriate handling or storage

could range from performance degradation to complete failure.

Data Transmission Rates

The reliability of a transmission system is directly related to the

accuracy and quality of the transmitted digital information. For a

digital system, those parameters which determine the limits of the

data transmission are pulse width distortion and propagation delay

skew.

Propagation delay is the time taken for the signal to travel through

the device. This is usually different when sending a low-to-high

than when sending a high-to-low signal. This difference, or error,

is called pulse width distortion (PWD) and is usually in ns. It may

also be expressed as a percentage:

This figure is almost three times better than for any available

optocoupler with the same temperature range, and two times better

than any optocoupler regardless of published temperature range.

PWD recommended by PROFIBUS, and will run at almost 35 Mb

before reaching the 10% limit.

Propagation delay skew is the difference in time taken for two or

more channels to propagate their signals. This becomes significant

when clocking is involved since it is undesirable for the clock

pulse to arrive before the data has settled. A short propagation

delay skew is therefore critical, especially in high data rate parallel

systems, to establish and maintain accuracy and repeatability. The

skew of 6 ns, which is five times better than any optocoupler.

PWD% = Maximum Pulse Width Distortion (ns) x 100%

Signal Pulse Width (ns)

For example: For data rates of 12.5 Mb

PWD% =

3 ns

x 100% = 3.75%

80 ns