Current shortage on 3V3P - Githubissues

sinara-hw / Sayma_AMC

AMC FPGA carrier board with FMC, dual SFP and RTM

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Current shortage on 3V3P #107

Closed kaolpr closed 5 years ago

kaolpr commented 5 years ago

In worst case scenario, when DDR termination draws maximum current and FMC draws maximum current allowed by FMC specification, MLVDS are used as well as both SFP we may have a severe overcurrent on 3V3 rail.

Budget assumes 4A and in such situation about 5.8A can be drawn (worst case). After quick chat with @gkasprow the following solution is proposed:

state that card is not fully FMC-compliant and 3V3 current shall not exceed 2A,
move SFP to P5V0 rail (adding buck converter).

Above steps will make worst case load slightly less than 4A.

gkasprow commented 5 years ago

Let's add individual 3A buck for FMC 3V3. NCP3710A which we already use would be fine.