For Additional Information About Optical Isolation verses a Standard IC on the Input of a Device see below

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ELM Video Technology, Inc.
"Innovative Midi and DMX Products"
http://elmvideotechnology.com

Input IC Comparison Table

Based on IC specifications.


	Standard IC SN75176AP	Optical Isolated IC 6N137	SN65LBC184	MAX3088E
Isolation Type	Electronic	Optical	Electronic - Transient Voltage Suppression	Electronic
Line Load (input impedance)	1/32 (apx 1.9mA Line Load)	1/2 (apx 25mA Line Load)	1/128 (apx .5mA Line Load)	1/256 (apx .25mA Line Load)
Fault Indication broken or loose wire	*Unstable (LED = unknown)	*Stable (LED = Off)	*Stable (LED = Off)	*Stable (LED = Off)
Fault Indication Open w/ Termination	*Unstable (LED = unknown)	*Stable (LED = Off)	*Unstable (LED = unknown)	*Stable (LED = Off)
DMX512 Conformity	Yes	**No	Yes	Yes

*Circuit design and environment affect the output

**6N137 does NOT conform to the DMX512 standards but should work with most systems.

For more information about DMX512 standards visit - http://www.usitt.org/DMX512.aspx

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The Advantages of Optical Isolation on the input of a device

Potentially higher voltage isolation protection than a standard balanced input IC
Current driven input - in the event that 1 of the wires of the 2 wire balanced DMX line stops working the output of the Iso chip will go high.

The Disadvantage of Optical Isolation on the input of a device ( See Texas Instruments web site chip # 6N137 for specs )

Requires a higher current than a standard balanced input IC. (Connect only 16 devices on the daisy chain instead of the normal 32). If the Opto device is connected directly out of the console this should not be a problem.

The Advantages of TVS Isoloation IC (75184) on the input of a device ( See Texas Instruments web site chip # SN75LBC184 for specs )

Offers protection between the output device and the input device using Transient Voltage Suppression.

Hi Z input (less line load on the daisy chain)

Without a connection (floating input) the IC has a high output - won't send miscellaneous data

The Disadvantage of TVS Isoloation IC (75184) on the input of a device

The 75184 IC or a standard input IC - if 1 of the wires of the 2 wire balanced DMX line stops working the output of the IC is miscellaneous (unstable)

The Advantage of True Fault IC MAX3088E on the input of a device

The MAX3088E IC is a TRUE FAULT INDICATION IC that gives a true data/active indication in any condition: OPEN, OPEN w/ TERMINATION, SHORTED, or ACTIVE.
High Z input, could have 256 inputs daisy chained.

The Disadvantage of True Fault IC MAX3088E on the input of a device

The MAX3088E IC offers only electronic isolation from input to the output of the IC.

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