LVTTL to SPDIF

[Ardee]

Can anyone advise as to the best way to convert low voltage TTL to SPDIF, please? Quality is more important to me than cost/complexity.

Thanks.

 

[bocka]

Use a 74LV86 (or similar XOR-Gate) to obtain a SOUT and /SOUT signal. Use this differential signal to feed an AD8132 high-speed differential op-amp and use a balun SPDIF output transformer.

 

[novec]

Does this compete with regular DITs like the Burr-Brown DIT4192 from TI? I do like the simplicity of it, and all I need is TTL-S/PDIF buffering, no sample rate conversion or anything.

 

[Ardee]

I think the DIT4192 converts I2S plus user bits to SPDIF. My question was how to convert LVTTL SPDIF to something which will drive a 75ohm interface.

Thanks for the suggestion bocka , btw.

 

[novec]

Of course, my bad.

 

[rfbrw]

My question was how to convert LVTTL SPDIF to something which will drive a 75ohm interface.

CLC001

 

[nonoise]

Just keep in mind that the output level should be 500mv P-P into 75 Ohm +/- 20% This is if you prefer to keep to the standard (IEC60958-3)

 

[gmarsh]

Use a 5V powered HCT gate (74HCT04, Tinylogic chip, etc) to convert LVTTL to +5V CMOS. You can use a faster logic family (VHCT, ACT) but be careful with decoupling.

On the output of the gate, put a 0.1uF series ceramic capacitor for DC blocking, then a resistor divider of a 330 ohm series and 100 ohm shunt.

(Actually, re-arrange that - put the 330 ohm resistor directly at the output pin of the logic gate, followed by the series capacitor and 100 ohm shunt.)

This gives you a 1.5Vpp unloaded, 0.75Vpp loaded SPDIF output with a near-75-ohm source impedance.