ReviewFineDelayFMC10112010
Schematics layout review held on 10 November 2010
Present: N. Voumard, P. Alvarez Sanchez, M. Cattin, E.van der Bij - CERN
Files used for the
review:
https://www.ohwr.org/project/fmc-delay-1ns-8cha/tree/7/trunk/circuit_board/fmc-delay-1ns-8cha/Schematics
General*
- No DRC check crosses on unused inputs and outputs are not systematically placed.
Page 1*
- 50 Ohm input termination should not use a jumper as this will not be accessible. Make it programmable via the FMC connector.
- TRIGSEL should not use a jumper as this will not be accessible. Make it programmable via the FMC connector.
- Remove note with text "Add termination jumper".
- The LEDs should not be directly on Trigger_select and termination. Run both from the FMC connector. Use for at least one would be to signal incoming triggers and therefore needs to come from the FMC connector (extended pulse).
Page 6*
- The input level is not TTL (as specified), but is LVTTL. Now when entering a 5V signal, the diodes will continuously conduct, while not being protected in any way. The fuse will not trigger (or even worse, it maybe even will switch off) and there is no resistor limiting the current.
- Can the input fuse handle the bandwidth and short pulses? It is a device made for power use, not signal use. Or, dependent how it behaves it may heat up and increase resistance dependent on the input signal it receives and therefore may introduce a phase delay.
- What is the footprint of the fuse? Can it be replaced by a simple resistor when needed?
- The inputs of the input multiplexer IC17 (FET switch) are wrongly connected (signal 1D- can only go to unconnected D- output).
- Consider to use a single ended type multiplexer with output buffer (the one now used is a FET switch) so that the output level is well defined.
- The 47 Ohm input termination is in 1206 package and likely is too small to dissipate if a continuous high level is used. Check the fast ADC card , R129, 56 Ohm in 2512 package. See also ADC issue.
- Symbol MC100EPT20DTG (IC5) has the flash in the wrong direction on the input pin 7.
- Symbol 74AC74M (e.g. IC14) has CLR and PR texts rotated and overlapping.
- IC14A is a D-register. The reviewers think a simple buffer would be better. Explain why use a register here.
Page 7*
-
Add a note in the schematic explaining the power supply compensation circuit of the TDC-GPX. Notably the supply VDD_TDC is not part of the diagram used in the datasheet and very different from using a Schottky diode. Consider prototyping without the 'compensation' on VDDC_TDC.
-
Even when the VDDC_TDC supply is 'compensated' like VDDC-H/O, it seems that C22 and R16 are connected to the wrong place and should be connected to the ADJ input of the regulator.
-
Using 100uF as decoupling is overkill. They are not recommended in the datasheet and there are anyway already many 47uF capacitors.
-
Suggest to add 100nF decoupling C's like normally used.
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Inputs of TDC-GPX not used correctly. E.g. Alutrigger and Tstop5-8 need a 10KOhm to Gnd instead of direct connection. See table starting at page 11 of the datasheet
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For readability use similar schematic layout for termination of TDC_STOP as used for TDC_START.
T O B E C O N T I N U E D
Erik van der Bij - 11 November 2010