Re: 24-bit 100kHz A-D converter with optical output

David L. Jones wrote...
>
> Winfield Hill wrote:
>> David L. Jones wrote...
>>>
>>> Hi Win,
>>> We used the (pre-release) CS5372 24bit ADC with a CS3302 front end diff
>>> amp, a CS4373 24bit test DAC, ADG734 MUXes, and an AD780 reference.
>>> This was for a 10,000+ channel seismic data aquisition system.
>>
>> Whew, did you have 10,000 A-D converters?
>
> Yeah, a big Seismic boat (for deep water oil exploration) can tow 8 or
> more "streamers" up to 8-10km in length each. Each streamer can have a
> thousand or more Hydrophone channels spaced at regular intervals. Each
> channel has to have a 24bit ADC, 24bit test DAC, and associated
> switching to allow for full testing of THD, noise, sensor capacitance,
> leakage and so on. Cost just for the front end electronics alone is in
> the order of US$100/channel.
> All the channels across all the streamers must be fully syncronised and
> sampled continously in real-time. The boats operate 24/7 for months on
> end.
>
> Interestingly, the system size is ultimately limited by the power
> consumption. Losses over 10km of streamer are huge, 500VDC in one end,
> <100V at the end. So the DC-DC converters for each module must operate
> over this entire range. It's all a big trade-off, more copper = more
> weight = more floation material required = bigger diameter cable =
> less total length = less streamer the boat can carry etc. Higher
> voltage = more difficult to design DC-DC converter = lower efficiency
> over the whole range etc...
>
> Total power consumption per channel is critical. The ADC might be only
> 25mW at full bandwidth, but by the time you add everyhing else up it's
> more like 1W/channel.
>
> The highest performance ADCs and DACs you can get are designed
> specifically for the Seismic industry (land and marine). Cirrus are
> major players and are ADC of choice in the industry.

I'm interested in the 100-500V input DC-DC converter, what output
voltage(s) did it have, how'd you keep it quiet enough to work with
the 24-bit A/Ds? Was its clock synchronized with the A/D clock?


--
Thanks,
- Win
.

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