Serial Power Overview
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Transcript of Serial Power Overview
D. NelsonOctober 7, 20082
Serial Power
Serial power is a viable option but…Must be evaluated on a system by system basis.
There are always advantages and disadvantages for different solutionsMust consider in all cases
Grounding and shieldingSystem stabilityNoise performanceSegmentationReliabilityTransmission line integrity
Several high speed protocols use AC couplingCML, LVDS, etc
D. NelsonOctober 7, 20083
Serial Power Example
Current RegulatedPower Source
Shunt regulator Series Regulator
Two ofN
HybridsIn
series
D. NelsonOctober 7, 20084
Six-module stave (finished; LBNL/RAL)
-operating reliably with multi-drop control/command cables
-Low noise despite some compromises
-Can run from a single HV line
Interface PCB Cooling hoseswith connector
Module 0
Module 1
Hybrid 2
Module 3
Module 4
Module 5
D. NelsonOctober 7, 20085
30-module stave (LBNL)
might become the largest serial powering stave ever built
so far looking very good in terms of SP
4 V x 30 hybrids = 120 V (0.8 A)
In future systems: 1.5 V x 20 hybrids = 30 V
6-chip hybrid with SP on 3 cm long silicon sensors
Chain of 30 hybrids is working fine
Module stave is being built up
D. NelsonOctober 7, 20086
Serial Power Advantages (1)
Reduced cablingCurrents are reduced significantly
Component requirements such as connectors and pins are reduced.
Smaller volume of servicesSmaller cables & connectors
Reduced Radiation lengthSmaller wire gauge cablesLess PWB copper for power distribution
More reliabilityLess demand for high current connections
Better power efficiencyLower currents
Doesn’t require switching power supply located near the preamplifiers and detectors.
D. NelsonOctober 7, 20087
Serial Power Disadvantages (1)
Little/no experience in physics communities.Must AC couple or use fiber communications.
Must maintain enough DC balanceInsure that data ALWAYS has enough transitions to recover dataUse 8b-10b or other encodings schemes.
Need to consider coupling capacitors’ stored energy.Ensure that power up, power down, and fault conditions don’t destroy electronics.
Minimize coupling capacitor sizes.
Should include ground fault circuitryYou want all of the current going through the intended electronics and not taking a short cut.Sections of electronics are tens of volts from detector grounds.
D. NelsonOctober 7, 20088
Serial Power Disadvantages (2)
High voltage biasing may present issuesDetectors will see different biasing if using a common external HV source
Could develop HV locally on the serially powered section
Not all that easy developing clean HV without iron core inductors.
An open could occur that acts much like the series Christmas tree light failure.
D. NelsonOctober 7, 20089
Conclusions
Need to take a close look at requirements to see if serial power is appropriate.
Serial power can work.We have some operational experience at LBNL on silicon strip detectors. (slide 5)
No hybrids broke during many power cycles to date
Noise performance is good.
AC coupling of LVDS works.