hi joe, i like your idea: 48V-->12V-->pico
it simpler and cheaper than 48V--->5V and 48V-->12V and 3.3V-->Roach and you don't have to worry about sequencing. best wishes, dan On Fri, Jan 20, 2012 at 10:18 AM, Joseph Greenberg <[email protected]>wrote: > Thanks for the replies Dan, Francois, and John, > > We will be drawing power from the correlator. > We have 3.3 Volts at substantial current available. > 5 Volts at limited current (less than an amp) so it would not be of use. > We can add a jumper to provide 48 Volts. > > It was mentioned that the sequencing of the power was important. If we > use our existing 3.3V and the > 48 V to generate 5V and 12V, then if the 48 V is unplugged there could be > only 3.3V. Would that be a problem? > > I am tending towards using the 48V to a DC-DC converter to give 12V. Then > routing the 12V to the Pico device to supply all the power. > This would eliminate using the on-board 3.3V. Too bad tthe Pico device > doesn't come in a 48V model. > > Thanks for all the help, > Joe > > Dan Werthimer wrote: > >> >> hi joe, >> the DC-DC converters are standard on the roach boards, >> so you only need to supply 3.3, 5 and 12 volts to the ATX connector. >> if you use john ford's $30 pico-PSU-90, then you only have to supply one >> voltage: +12 Volts at 8 amps. >> i'm not sure about the maximum currents for each of the roaches three >> input voltages. >> i'm cc'ing the casper lists - someone will know. >> i can measure these currents with our clamp on amp-meter, but these will >> change a bit, depending on how heavily you load the FGPA and what >> ADC's are plugged into the roach board. >> best wishes, >> >> dan >> >> >> >> >> On Thu, Jan 19, 2012 at 10:53 AM, Joseph Greenberg <[email protected]<mailto: >> [email protected]>> wrote: >> >> Hi Dan, >> Thanks for the reply. >> >> Dan Werthimer wrote: >> >>> >>> hi joe, >>> >>> can you leave the DC-DC converters on the roach board? >>> >> Yes. Are they standard on all Roach I boards or do we have to >> specify them? >> >>> then you only need to supply the 12, 5 and 3.3 volts that >>> come from the ATX power supply. >>> >> What is the maximum current we would need to supply for each of >> these Voltages? >> >> Thanks, >> Joe >> >> >> >>> best wishes, >>> >>> dan >>> >>> >>> On Thu, Jan 19, 2012 at 10:28 AM, Joseph Greenberg >>> <[email protected] <mailto:[email protected]>> wrote: >>> >>> We at NRAO are going to mount the Roach I board on a custom >>> board, rather than using the usual chassis. >>> We will have DC-DC converters on the board. >>> The Roach documentation states: >>> Voltages of 12V, 5V, 3.3V, 2.5V, 1.8V, 1.5V, 1V and 1.2V aux >>> rails. >>> >>> Is there any specification of what maximum currents we need >>> to supply for each voltage? >>> >>> Thanks, >>> Joe >>> >>> >>> >> >> >
