... | ... | @@ -15,7 +15,8 @@ be discussed are: |
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- PCB received from DEM
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- Issues found: like 3V3\_IC7 power plane, small\[?\] 1V2 plane
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for FPGA, FOD060L replacement, VME64x spacings.
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for FPGA, FOD060L replacement, adding buffers for the RTM
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passive and pins in FPGA.
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## Schematics
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... | ... | @@ -23,19 +24,19 @@ be discussed are: |
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Different isolation connections are found at CERN. However, there's not
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an strong agreement of how to specifically do this for the case of
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either the Blocking boards or the next RS-485. A couple of good
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either the Blocking boards or the next RS-485 ones. A couple of good
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references for gaining insight are "Goods for grounding"\[1\], which
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gives a from a system point of view how to solve grounding issues, and
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"Noise Reduction Techniques in Electronics Systems"\[2\] that offers a
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quick and straightforward technical approach for cable grounding.
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offers a system point of view for solving grounding issues, and "Noise
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Reduction Techniques in Electronics Systems"\[2\] that offers a quick
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and straightforward technical approach for cable grounding.
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The isolation problem found in the schematics lies in the floating state
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of both the driver and the receiver, which as pointed out in \[1\], can
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yield problem for an operator. Thus, an acceptable schema for the
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Blocking board can be as follows:
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The **isolation problem found in the schematics** lies in the ground
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floating state of both the driver and the receiver, which as pointed out
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in \[1\], can yield into shock and spark hazard (\[1\] section 4.2.2.1).
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Thus, an acceptable schema for the Blocking board can be as follows:
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- Driver will be isolated (via couple inductors)
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- Receiver must be grounded
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- Receiver must be grounded, so as BLO- input pin (cable shield).
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\[2\] explains that for low frequencies, like the ones expected for the
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Blocking case (\< 10MHz), breaking the ground loop by only grounding at
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... | ... | @@ -62,8 +63,17 @@ CONV-TTL-RS485 projects. A pinout proposal can be found |
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## Layout
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Issues found:
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Main issues found:
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- Plane 3V3\_IC7 \> Plane 3V3
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- Possibly 1V2 can be bigger layouted
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-----
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\[1\] "Grounds for Grounding", Elya B. Joffe
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\[2\] "Noise Reduction Techiniques in Electronic Systems", Henry W. Ott
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-----
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Carlos Gil Soriano - 19 January 2012
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