Review02032010 improvements
This page shows the replies to the Review02032010 and the improvements made.
Detailed comments on schematics
Sheet 1: High Pin Count Connector
- LA00_CC_P should be called LA00_P_CC (same for N). Change also
where this signal is used.
- Name haven't been corrected, because of the way how Altium Designer recognizes differential pairs. Positive line's name needs to be P-ended and negative one needs to be N-ended. CC-ended line's names do not follow this Altium's rule. It is decided to use for ex. LA00_CC_P instead to LA00_P_CC (which follows the VITA 57 standard).
- VIO_B_M2C is not used: remove signal.
- Done.
- Remove all signals that are not used in the design to prevent
confusion.
- Done.
- Mark the meaning of B1-B4 and FIG1-FIG6.
- Mark LA23_N/P to be a differential pair.
- Done.
- Check if LA06_P/N are correct (pair, both signals used?).
- Done. They aren't treated as a pair, but both of them are used.
Sheet 2: Input stage
- Sheets 3, 4 and 5 should be the same. This has not been verified.
Make sure all modifications are done on all channels.
- Done.
- Consider inserting an inductor at the negative input to make it
symmetrical to the positive input (verify AA's mail about this).
- It is not necessary. The signal filtering at the input only is enough. Adding another filter is just like a filtering in the feedback loop. May cause instability of the differential amplifier.
- Add a note on the input ranges, voltage ranges at critical points in the schematic. This should also make clear that it's an input range of 10V (Vpp) with a programmable offset between -5V and +5V. Possibly give examples of usage to clarify.
- If 50 Ohm setting: +/-7.5V maximum.
- Add names SW1-SW7 in schematic (refer to sheet 11).
- Done. "Menu" -> "Tools" -> "Schematic Preferences" -> "Graphical Editing" -> "Single '\' Negation" has to be highlighted.
Sheet 6: Linear Technologies' ADC
- Add a note about the different frequencies of DCO, FR, ENC.
- Done.
- Add 2 resistors to select the sensitivity of the ADC (SENSE): 100
Ohm to Vdd, 100 K placeholder to Gnd (normally not mount).
- Done.
- symbol misses overline on CS.
- Done.
Sheet 7: DACs and Vref source
- Add comments on ranges of signals.
- Add 100nF on +12V_filtered of ADR445 (IC2).
- Add 100nF on supply of ADA4004 (IC5 DAC buffers).
- Check if the ADC can give out a status on the SDO pins. If so, connect it to the FMC connector.
- Use the B version of the reference voltage generator ADR445ARMZ. These have a better temperature stability (verify and verify price difference).
- EP (external pad) of the OPAMP should be connected to the negative supply voltage instead of the Gnd. Check with datasheet.
- The DACs are supplied with +6V while this is the absolute maximum voltage. Check if they should be supplied with a lower voltage and how it should be generated.
Sheet 8: I2C memory and LED indicator
- Redo the trigger input stage so that it can withstand a +/-10V input signal as users can by mistake connect an input signal to this connector.
- R117 56 Ohm trigger input termination resistor: use a 0.5 Watt type.
- Verify dissipation capability of R116.
- Change LEDs into green types.
- Add texts to LEDs: Trig'd, OK.
- Add thermometer IC. This can ultimately be used to add a temperature compensation. The same chip should also provide a unique serial ID.
- Verify if the memory is large enough to store all calibration parameters.
- Put the value of R118/R119 next to component.
- Document input levels and trigger level.
Sheet 9: Power supplies
- Add 10pF C to SET input of LT3080.
- Replace 60K4 SET resistor by 600K to have correct 6V output.
- Replace C46 1uF by at least 2.2uF.
- Symbols shutdown pins of IC9 and IC10 are not marked with active low marker.
- IC8 LT3080, pin EP should be connected to Vout and not to Gnd. Check datasheet.
- C48 (220pF on LT1931 output) should have a different value to match phase lead zero. Check datasheet.
Sheet 10: ADC clock generator
- Replace symbol by Si570 and re-verify with someone else.
- Add note on the I2C address.
Other comments
- Make a Bill-of-Material and verify if the number of different components can be reduced.
- Calculate the total component costs.
- Print out the netlist and verify it by hand to make absolutely sure that all signals are connected with the right number of pins.
- Add the datasheets of all used components in EDMS (Ordering info).
- Make sure that the capacitors are of the X7R type.
Additions to the manual
- Add a note about the crosstalk: do not put an input with a /-5V range next to one with a/-50mV range.
- Specify input ranges, maximum voltage with 50 Ohm setting, etc (see comments for Sheet 2).
PCB layout (preliminary review)
- Move IC8 12V to 6V drop-down converter to the other side of the FMC connector. This way it can be cooled by the stand-off pin (it dissipates 0.9 Watt).
- Consider placing the filter inductors alternatively on the top and bottom side to reduce coupling.
- Pay attention to ENC inputs of ADC: coupling capacitors should be very close to have no stubs.
- It seems that the LEDs and the connectors are too much advanced and will touch the front-panel.
- Use solid ground planes.
- Seriously consider to use power planes instead of using tracks.
- Verify the switching supply layout.
- Maciej Fimiarz - 4 March 2010