Hello all,
I'm working with DIR1701 as receiver. However, it's D_in only accept CMOS level, I need to convert SPIDF signal into CMOS level.
TI (on DEM-DIR1701 instruction manual) suggest using a two stage 74HCU04 buffer to do the level convert. Is there a better way to do it? Or are there any "low jitter" gates for building the buffer??
Thanks in advance.
I'm working with DIR1701 as receiver. However, it's D_in only accept CMOS level, I need to convert SPIDF signal into CMOS level.
TI (on DEM-DIR1701 instruction manual) suggest using a two stage 74HCU04 buffer to do the level convert. Is there a better way to do it? Or are there any "low jitter" gates for building the buffer??
An externally hosted image should be here but it was not working when we last tested it.
Thanks in advance.
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Guido,
About the Opamp approah. Do I need to add bias to the SPDIF signal before feeding it to the Opamp? I mean offsetting the "bipolar" +0.25/-0.25V input signal into "single-ended" +2.75/+2.25V, before amplification.
Or should I run the Opamp with +5V single supply and simply clip the output to +5/0V?
About the Opamp approah. Do I need to add bias to the SPDIF signal before feeding it to the Opamp? I mean offsetting the "bipolar" +0.25/-0.25V input signal into "single-ended" +2.75/+2.25V, before amplification.
Or should I run the Opamp with +5V single supply and simply clip the output to +5/0V?
S/PDIF Input
You can't use most op-amps because the signal is in the 6 MHz range. If the lvel is too high coming from your source, you can attenuate it with a resistor. However, I use a 74AC04 operating on a 3.3V supply to buffer the input on my unit. You don't need anything fancier. On the electrical input, I couple the S/PDIF signal through a DC blocking capacitor to the input of the 74AC04 through a 220 ohm resistor. The input is biased with two resistors to 40% of the supply voltage.
On my opto input, the output of the TORX141 is buffered through another section of the 74AC04.
You can't use most op-amps because the signal is in the 6 MHz range. If the lvel is too high coming from your source, you can attenuate it with a resistor. However, I use a 74AC04 operating on a 3.3V supply to buffer the input on my unit. You don't need anything fancier. On the electrical input, I couple the S/PDIF signal through a DC blocking capacitor to the input of the 74AC04 through a 220 ohm resistor. The input is biased with two resistors to 40% of the supply voltage.
On my opto input, the output of the TORX141 is buffered through another section of the 74AC04.
A little sharing, though most of you might already know. TTL gate does not work in the case of U3 on DEM-DIR1701 instruction manual. The first gate is actually a linear amplifier and only CMOS gates are suitable for doing this.
Before I learned this, I tried 74F04 and 74LS04. No matter how I bias the input DC, these TTL gates won't have symmetric output duty cycle. And they don't amplify, instead they simply switch on or off.
Finally, I settle on ADM1485. It's plug and play, trouble free. Thanks Andrei.
Before I learned this, I tried 74F04 and 74LS04. No matter how I bias the input DC, these TTL gates won't have symmetric output duty cycle. And they don't amplify, instead they simply switch on or off.
Finally, I settle on ADM1485. It's plug and play, trouble free. Thanks Andrei.
An externally hosted image should be here but it was not working when we last tested it.
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