Difference between revisions of "Novena AFE"
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*Capacitive loading of VCMO is too large for 0-ohm stability with buffers. Replace R10I, R11I with 620 ohm, 1% resistors. Some tuning could be used later on, e.g. values were chosen conservatively large for stability, but if ripple appears on the line consider reducing resistor to improve ripple performance. | *Capacitive loading of VCMO is too large for 0-ohm stability with buffers. Replace R10I, R11I with 620 ohm, 1% resistors. Some tuning could be used later on, e.g. values were chosen conservatively large for stability, but if ripple appears on the line consider reducing resistor to improve ripple performance. | ||
| − | ===Loop filter tuning=== | + | ===Loop filter tuning (all variants)=== |
Generated using ADIsimCLK - save file ad9520-3-calck.clk | Generated using ADIsimCLK - save file ad9520-3-calck.clk | ||
*C38C 1500pF -> 82pF | *C38C 1500pF -> 82pF | ||
Revision as of 10:08, 10 March 2014
Notes on Novena AFE
Contents
EVT bringup notes
All variants
- R17P is wrong. The current value of 45k sets the output to 3.3V. Should be 52.3k to set the output to 3.7V
- R21C, R20C is too weak. Set to 1k to overcome the internal bias on SP0,1
High speed variant
- Capacitive loading of VCMO is too large for 0-ohm stability with buffers. Replace R10I, R11I with 620 ohm, 1% resistors. Some tuning could be used later on, e.g. values were chosen conservatively large for stability, but if ripple appears on the line consider reducing resistor to improve ripple performance.
Loop filter tuning (all variants)
Generated using ADIsimCLK - save file ad9520-3-calck.clk
- C38C 1500pF -> 82pF
- R23C 3k -> 2.7k
- C37C 4.7uF -> 3.3nF
- R25C 2.1k -> 1.3k
- C36C 2200pF -> 270pF
- Loop bandwidth: 102 kHz
- Phase margin: 43.6 deg
- Zero: 37.1 kHz
- Pole: 275 kHz
- Last pole: 951kHz
Estimated phase noise and jitter to ADC:
Frequency: 1.00000GHz
Broadband Jitter (>1kHz) = 558fs rms
SNR = 69.10dB ENOB = 11.52bits
at IF Freq = 100MHz
Integrated Phase Noise from 100kHz to 1.25MHz
Timing Jitter = 302fs rms
Phase Jitter EVM = 0.19 %rms
Phase Jitter = 0.109 degrees rms
ACI / ACR = -57.5dBc
Delay from Ref to OUT3 is 250ps
DAC-specific
U14A footprint is flipped. Must rework before power-up.
