V2 schematics review, January 2014
Reviewer:* T.Wlostowski
Commit:*
490f3b2f
General
- Altium complains about missing files: FMC.Harness.
- Missing title block contents (please use standard CERN EDA document template)
- Make names consistent (Ux vs ICxx for ICs, etc.)
- Clean up (wires over components, etc.)
- Use one symbol for all power nets and ground nets. There is a bar and "earth" ground in use, same for the powers (bar, arrow, circle).
- Make power net naming more precise. E.g. P3V3_CLEAN-> P3V3_AD9516, P3V3_PLL (in fact it powers the ADF4002 PD) -> P3V3_PD, P3V3CLK -> P3V3_AD9510.
FMC Connector
- DIN -> DELAY_IN
Trigger
- U22: DE and \RE pins should be connected to P3V3D, otherwise the buffer will be permanently disabled.
Clocking
- PLL_REF_SEL goes nowhere. Since this pin is not needed, place a no-error marker.
- Same for PD and \REFIN pins.
- Net REF_CLK (25 MHz VCXO) - the name is a bit confusing, as there are multiple reference clocks in the design. Figure out a more precise name.
- OUT0: place coupling caps close to the output of the PLL.
- An explanation of the loop filter component values would be very
appreciated (e.g. a note pointing to
Analog Device's simulation file) - Place labels with the default clock frequencies next to the PLL outputs.
Phase Detector
- Loop filter components: same as for the clock distribution PLL, explain the values or attach the AD simulation file and a link/note where to find it on the schematic.
Power
- Check the power dissipation of the P6V0 regulator - it's about 100-120 mA (corresponding to 0.6-0.8 W of power dissipation), so probably some extra cooling space will be needed on the PCB.
DAC
- Why a dedicated comparator for the FPGA clock output? Wouldn't it be simpler to use an AC-coupled LVPECL output of IC13?
- IC13: in AC-coupled mode, \CLK pin should be shorted with Vref and Vt pins.
- IC13: check input level. Jitter-wise, ADCLK944 doesn't like slow
edges in the
input signal (i.e. sine wave from the lowpass filter). Check "Clock inputs" section in the datasheet, page 9. - Cleanliness: loose net labels close to IC13.
- IC19: for full scale DAC output the amplifier will produce ~4 Vpp (unless its output is source-terminated). This exceeds the input range of the clock fanout.
- IC19: Match the output impedance of the amplifier to the filter (series resistor?).
- R8: Shouldn't it be after C76/C23 (LVPECL is usually not terminated with DC-coupled 100 ohms)?
- U11: Pin 11 (digital 3.3V) is connected to the analog power supply? Is this intended? Also, s/U/IC.
ADC Filter
- Are R4/C1 necessary if the ADC is connected already to the PD's lowpass filter output?
Delay
- R15/R42: AFAIK in order to bias a bipolar LVTTL output, one should use small pulldown resistors (I used 470 ohm in the Fine Delay).
- The pulse output will drive a rather small voltage on a 50 Ohm load (less than 1.5 V). Is this OK?
VCXO PLL
- Pin NC in OSC2 is the tuning voltage. Update and check the symbol.
Top level
- Unconnected SCL, SDA ports in the FMC connector
- Add most important net names on the connections on the block diagram. This will make the design easier to follow.