[time-nuts] STEL 1175 vice 1173

Ed Palmer ed_palmer at sasktel.net
Wed May 14 12:53:27 EDT 2014


Hi Corby,

Thanks very much for the offer, but it looks like it would still be a 
big project to use an '1175 to replace an '1173.  I think I'll have to pass.

The package difference (PLCC68 vs. PLCC44) would still require a 
daughterboard of some sort.  I've learned a little over the past week 
about NCOs and, if I'm right, reducing the clock speed from 45 MHz to 30 
MHz would partially compensate for the 32 vs. 48 bit difference.  The 
output frequency would be correct, but the waveform would have more 
harmonics.  Since the clock is derived from a 90 MHz signal, the 
reduction would be easy.  Whether that would have an adverse impact on 
the operation of the Datum 4065A is way beyond me.  It looks like both 
chips have a 12 bit output which is nice. The '1175 has more features 
than the '1173.  I'd have to study the data sheet to see if they can be 
configured to make the '1175 act like an '1173.

For now, the plan is to try and source the '1173 in the 48-pin DIP 
package and do a (relatively) simple daughterboard to adapt the 
packages.  Even that will probably end up costing ~$150.  If that 
doesn't work out, there's the possibility of an FPGA replacement. That 
would likely allow replacing the AD9713 D/A converter as well as the 
STEL-1173.  It turns out that an NCO is a standard application in the 
FPGA world.

Ed

On 5/14/2014 9:13 AM, cdelect at juno.com wrote:
> Hi,
>
> I found two PLCC STEL 1175 in a rack mounted synthesizer I have.
>
> I'd be willing to sell the chips.
>
> Would they work?
>
> Cheers,
>
>
> Corby



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