alec(at)alecmyers.com
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 Posted: Fri Oct 20, 2017 9:13 am Post subject: Constructing an automatic RCA video camera feed splitte |
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The code is 90% done. I’ll do the other 90% in due course.
On Oct 20, 2017, at 11:53, Eric Page <edpav8r(at)yahoo.com> wrote:
alec(at)alecmyers.com wrote:
| Quote: | I think we’re ok. That section is either wrong, or badly written, I can’t work out what it’s trying to say either. But:
Look at table 1 in para 8.4 - control L gives High-Z at the output.
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True, and that line of Table 1 is the most recent item on the revision history. However, the second paragraph of the intro (Sec 3, pg 1) and paragraph 8.1 (pg 14) are consistent in their description of the outputs; that is, tied to either Vdd when Vc is high, or to Vss when Vc is low. I presume "high" means Vc = Vdd and "low" means Vc = Vss; that's certainly what many of the diagrams suggest.
If, as Bob says, the NTSC signal we're working with is DC biased and exists entirely above 0V, then we can use a single supply and it shouldn't be an issue. That will simplify the schematic, shrink the BoM and ease the layout.
There are apparent errors elsewhere in the datasheet as well. Fig 5 (pg 9, Typical ON Characteristics) includes a wiring diagram that shows -- as you would expect -- Vc = Vdd. However, Fig 9 (pg 10) depicts the test setup for this measurement and it shows Vc = Vss = -5V. Then Fig 10 (pg 11, OFF Switch Input or Output Leakage) shows exactly the same setup, with Vc = Vss. Apparently the outputs can be ON or OFF with the control high or low. This must be a quantum device!
This datasheet is a mess.
I guess we stand by for results of Bob's test with a sample camera, and Wade's test with multiple cameras through a switch...
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473706#473706
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