Replace LTM4620 DC-DC converters with LTM4619
After detailed measurements on FTRN's power rails and estimates of
maximum current consumption on the PMC prototype, we decided to replace
the LTM4620 DC-DC converters with LTM4619.
Also after taking into account the design differences between PMC, AMC and VME, we intend to replace LTM4620 with LTM4620 on all three FTRN form factors.
In discussions with GSI so far, there were no objections to such
@Dietrich, please acknowledge the change, we can Skype if you need more deails.
Here are our reasons, explanation and measurements, perhaps it's interesting also for your designs:
- when running all IOs at 200Mhz, WR lock, etc on PMC, we are near maximum power consumption, prescribed by the PMC standard (7.5W).
- by replacing the switchers, we will conserve 1.4W power, because LTM4619 has substantially lower power dissipation in idle state than LTM4620 (0.5W on 4619 vs. 1.9W on 4620)
- also, we'd like to lower the heat dissipation on the board
- LTM4619 is a safe choice, because even if we estimate 200% margin over measurements with current FPGA design, the consumption would not exceed 55% of LTM4619 capacity (see FTRN_PMC_current_consumption_by_voltage_rail_measurement.docx)
- in FTRN conditions, LTM4620 operates in very low efficiency, being designed for 13A but using <1A.
Attached are more details about measurements and conclusions: FTRN_PMC_current_consumption_by_voltage_rail_measurement.pdf