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Interfacing microcontroller to 1GBPS laser driver

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GeoAVR

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Dear all,

I want to interface a microcontroller with the MAX3798 laser transceiver ic.
The problems are:
1. The MAX3798 has CML (current mode logic) for transmit and receive data but the microcontroller uses 3.3V or 5V voltage logic.
2. The minimum data rate of MAX3798 is 1GBPS but the microcontroller has 150MHz clock.

How can I solve these problems?



Thank you
 

barry

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1) You're going to need a level translator to go from TTL to CML
2) Your microcontroller is not going to work with 1GBPS data unless it has an internal PLL or some other way to increase its internal frequency.
3) So you don't a level translator after all.
 
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GeoAVR

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I don't need to use the full 1GBPS Bandwidth, just a few MBPS is fine, but the laser driver IC is for 1GPBS applications.

Do u think a Serializer/Deserializer (SERDES) will help?
 

barry

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Your original post said: "2. The minimum data rate of MAX3798 is 1GBPS". But you want to run slower than what you've already acknowledged is its minimum. Maybe you need to look at a different driver.
 
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mtwieg

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Even with a SERDES, does your MCU even capable of producing 1gbps of information?

Maybe you could try upconverting the output of the MCU with a mixer (an XOR gate?).
 
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    GeoAVR

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dick_freebird

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Given that the MAX3798 is so mismatched to almost every
aspect of your application, why are you so intent on using
it rather than some slower, cheaper, better suited laser
driver? Set the Wayback Machine to mid-'90s and you could
probably find 3.3V / 5V CMOS input drivers that will run down
to near DC.
 
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GeoAVR

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All VCSEL laser drivers that I could find operate from 1GBPS.
The MAX3798 is prefect for my application since it is both receiver and transmitter and it has programmable bias and modulation current.

Can someone propose another driver or mixer ic?

Otherwise maybe I should try and design my own driver for lower speeds.
 

barry

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I think we've already established that:
1) you can't run something slower than its minimum
2) you can't run something faster than its maximum

So you've got two choices: replace your processor( maybe with an FPGA) or replace your driver. Or maybe use something other than VCSEL
 

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