All,
Attached is a Excel/PDF outlining the current needs of the Pacsat system. The is based on the previous Fox design concept with some adjustments to match our needs. This is a first pass and the best information will come from testing since this is a dynamic system.
In the sheet I indicate the possible modes the TMS570 may operate in. I have not looked at the details of the two principal modes. The mode that requires the most current is the mode with Built In Self Test (BIST). After launch testing may not be useful to us as we will limited ability to correct for problems. The modes can be changed by changing register values. I can see a lot of development time may be needed to understand these modes and test the results of making any changes between modes. I would like to hear some comments regarding the earlier development for this device. We will want to know the impact of making any changes before firming up launch code packages.
In the PGE package we can operate the TMS570 up to 160 MHz in the pipeline mode. We can also reduce the clock rate and obtain a savings of 0.85 mA for every 1 MHz reduction in clock rate. Most of the current consumed by this part is provided by the 1.2 Volt supply line. If we drop the clocking rate to 100 MHz we can realize a savings of 51 mA or about 61 mW. This clock rate reduction will be limited by the ability to collect and process the data from the radio modems and memory devices. Testing with software in place will probably be needed to get an idea of what is required.
I am attaching a set of drawings for the first pass at a design for the AX5043 system. This includes 4 receivers and 1 transmitter. The transmitter is the same as the design used in the Fox program. The receivers are changed to to use a single antenna, filter with a bandwidth to cover the 2m operating band, preamp, and power divider. More work is needed on all this as well but I wanted to show some progress.
There may be enough flexibility in the AX5043 chips channel selection to allow us to program four different receive frequencies while using a single reference oscillator. We may also need a clock reference generating system and I have started laying this into the design to be sure it is covered. I have not yet included in power requirements for these devices.
Bob N5BRG