Romantic Robot Videoface Digitiser (clone)

[matalog]

Hi matalog,

Take care to use the right chipset, especially the 74HC4074 (from Thomson!), other brand name are less adapted to the circuit on high speed signal.

I asked the clearance to distribute my PCB to McClaud, but no answers at now. (PM never read, PM full... from Sent: Sun Aug 04, 2024 8:12 pm)

Do you mean the 74HC4094's? I bought these ones: https://www.mouser.co.uk/ProductDetail/595-CD74HC4094E which look the same as the photo that was posted at the start of this thread

[XavSnap]

Hi matalog,

Sorry, it a Philips, not a Thomson.

Yours is a CD74HC4094E from TI (Texas Instrument)
https://www.alldatasheet.com/datasheet- ... 4067E.html

Philips CD74HC4094D:
https://datasheet.octopart.com/74HC4094 ... 568262.pdf

I can only explain this saturation of the inputs at high speed by the difference in voltage threshold and the precision of the component. Otherwise it will be necessary to adapt the inputs with a resistor, or put a capacitor to modify the shape of the chromatic comping signal.

fMax TI:1000ns=1mhz (VCC=2v)
fMax Philips:95mhz:1.0526315789474E-5 ms=10,52ns (CP to Qs= 15ns; Delay= 50ns=66mhz) (VCC=2v)



Something's wrong in the datasheet...

[matalog]

Thanks, I can see tht the OP stated Phillips IC's in the schematic. But I bought the same ones as in the photograph they posted.

Are you very confident that you are correct about the necessity of the Phillips 74hC4094's? And that the TI IC will definitely cause this problem?

Is there a small patch I can make to amend my current circuit to work?

[1024MAK]

Philips are no longer in the semiconductor business as far as I know. More details here. Although NXP have discontinued a lot of 74 series logic chips in DIP/DIL packages

Mark