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What is the max data rate at which this opto-isolator can used?

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matrixofdynamism

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The LITE-ON LTV-817 is a High Density Mounting Type Photocoupler. Its datasheet can be found here. I have found that datasheets of many opto-couplers do give the data rate. However, this one doe not. How do I find the maximum data rate that this can be used in?

With opto-couplers, the output uses a open collector output. This means that the transistor turning on shall ground the output but otherwise it shall remain floating. I assume that this severly limits how fast the opto-couplers can usually work? Perhaps only 100s of kilobits like in a PS/2 mouse. However, datasheets show that opto-couplers can achieve Mb of datarate. Strage.
 

There's usually no data rate specification in standard opto coupler datasheets because the achievable rate depends strongly on the application circuit. LTV-817 datasheet figure 10 and 11 allow a first estimation. As the small signal cut-off frequency clarifies (with 100 ohm load resistor!), you'll hardly achieve "100s of kilobits". Even 9600 baud can be an issue with unsuitable circuit.

Mbit per second are only achieved by fast "digital" couplers.
 

Hi,

Mind that with 100 Ohms you won't get valid TTL levels. You need an additional curcuit, like a comparator..

Klaus
 

With generic optocouplers, the main concern is to improve CTR.

High CTR can be achieved with high emission LEDs and/or wide-base phototransistors. Usually the latter approach is followed.

Wide-base means relatively large capacitance, which will limit your switching speed. Therefore the vendors are reluctant to provide a firm, guaranteed switch time value.

If you want a guaranteed switching value, which also will not degrade significantly over time, you have to select an optocoupler which has been optimized for switching speed.
 
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