Review02032010
Design review of FMCADC100M14b4cha
schematics version of 2010-02-26 16:29.16
Present
Michael Sordet (BE/BI), Matthieu Cattin, Pablo Alvarez, Erik van der Bij, Maciej Fimiarz (designer)
Review
General
Maciej gave a general overview of the design. It is optmised for noise
levels, that's why low value resistors are used and the input impedance
is only 1 KOhm (or 50 Ohm selectable). The stability of the gain and
offset is mainly influenced by the MOS switches.
The anti-aliasing filter has it's -3dB point at 25 MHz, with a 4-pole
filter. The sampling frequency is programmable on the local oscillator,
or can be coming from the FMC carrier (production option), but it is
supposed to be 100 MHz.
The lowest sensitivity setting of the ADC ( /- 1V) is used for noise
reasons. But for this the differential ampifier in front should amplify
by a factor 2. It is not clear if this is better than having the highest
sensitivity setting of the ADC (/- 0.5V) and have a unity gain
amplification in front.
Detailed comments
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.
- VIO_B_M2C is not used: remove signal
- to prevent confusion: remove all signals that are not used in the design
- Mark the meaning of B1-B4 and FIG1-FIG6
Sheet 2: Input stage
- consider inserting an inductor at the negative input to make it symmetrical to the positive input (verify AA's mail about this).
- Add a note on the input ranges, voltage ranges at critical points in the schematic.
Sheet 6: Linear Technologies' ADC
- Add a note about the different frequencies of DCO, FR, ENC
- Add 2 resistors to select the sensitivity of the ADC (SENSE)
Sheet 7: DACs and Vref source
- Add comments on ranges of signals
- Add 100nF on +12V_filtered of ADR445
Sheet 8: I2C memory and LED indicator
- Redo the trigger input stage so that it can withstand a /-10V input signal (or/- 5V?) as operators can by mistake connect an input signal to this connector.
- Change LEDs into green types.
- Add texts to LEDs: Trig'd, OK
Sheet 9: Power supplies
- Add 10pF C to SET input of LT3080.
- Replace 60K4 SET resistor by 600K to have correct 6V output
Sheet 10:
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.
PCB layout (prelinary review)
- 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.