* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download velo hybrid design notes
Electric power system wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Ground (electricity) wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power engineering wikipedia , lookup
History of electric power transmission wikipedia , lookup
Variable-frequency drive wikipedia , lookup
Electrification wikipedia , lookup
Three-phase electric power wikipedia , lookup
Power over Ethernet wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Power inverter wikipedia , lookup
Solar micro-inverter wikipedia , lookup
Alternating current wikipedia , lookup
Earthing system wikipedia , lookup
Audio power wikipedia , lookup
Amtrak's 25 Hz traction power system wikipedia , lookup
Voltage optimisation wikipedia , lookup
Power electronics wikipedia , lookup
Buck converter wikipedia , lookup
Opto-isolator wikipedia , lookup
Mains electricity wikipedia , lookup
velo hybrid design notes Power supply calculations for output power supply 1) assuming load resistors are placed on the module then 64 channels of output each switches 20mA when output starts so power supply current will change by 1.28Amps. when the outputs become active after a trigger. This will result in a voltage drop at the module which is approximately 1metre from the power supply card on the outside of the tank. Let us allow a maximum drop of 120mV in the supply voltage at the module with equal drops of 60mV in the supply and return. Note that this assumes a floating regulated supply at the power supply end and that the low side of the supply is grounded only at the module. Calculate conductor cross section in the kapton cable for supply and return: Assume 18um copper 1metre long Max resistance 50m Ohms R = Rho (Cu) * l -----------------a Width of conductor (m) = 1.77 e-8 ohm . m * 1m ---------------------------18 e-6 m * 50 e-3 ohm = 0.020m approx For 120mV drop we need 20mm wide traces Check power dissipation – 120mV * 1,2A === 144mW is this OK in vacuum? An alternative would be to simply take the drain and source connections of the output transistors as a 100 ohm line to the repeater How do we output signals from the velo The Velo chip has four output channels and one reference channel. Both the source and drain of the output transistors are available . This is similar to the output arrangement of the SCTA chip except that the SCTA has only one reference and one output channel. The SCTA output has in the past suffered from low frequency common mode problems due to sensitivity to the power supply voltage and time constants of the power supply decoupling. In order to overcome this power supply sensitivity I propose to decouple the reference level to the power supply so that supply movements are coupled equally into the reference and into the output signal. The proposed output configuration is as shown in the schematic below. Here it is assumed that the repeater amplifier/line driver is placed at around 1 metre distant from the hybrid and is connected via a kapton cable of 100ohm characteristic impedance. Note that it may be difficult to achieve this value ( approx 4 thou track over a return on the opposite side of 200um of kapton with an Er of 3) if this proves impossible then a smaller value may be chosen around 75 ohms. The impact of this will be that for correct matching the output and reference transistors will need to be biased with equal load resistors and the output voltage swing will be reduced. In the circuit it can be seen that the differential pairs are terminated at the repeater in a high impedance rather than in 100ohms in the present SCT configuration so it will be necessary for the amplifiers to include the positive rail in the input common mode voltage specification. A simulation of the circuit below for two channels gives good performance both for high frequencies and for low frequencies with virtually no common mode injection between channels and good immunity to power supply noise. Note that there is decoupling of the reference node to the power rail and not to ground giving good supply rejection. Note that there is no requirement for large decoupling of the supply to ground at the hybrid, at least in the simulation. In practice a few nF of capacitance across the supply may be a good idea from the point of view of stability. The good supply rejection also removes the need for a sensed supply for the output circuits although the supply must be floating and connected to system ground only at the hybrid. VELO output simulation (2 channels) 10 R1 simulates power line impedance 100 R2 100 R7 100 R4 100n C1 4 V1 T1 chan1 Probe 1Meg R3 Z0=100 TD=5n I3 20m I2 20m I1 1m Pulse(0 20m 0 500p 500p 25u) T2 Z0=100 TD=5n 1Meg R5 chan2 Probe1