P12V EEM rated power

[martafafara]

Last modification to fix #80 has limited current provided to EEMs to the value of 2.81A. This value meets requirements placed as note in schematic sheet (next to J25), but is not enough to power up all EEM cards simultaneously. Any particular value has not been declared, but current limit of 20A like in EEM Power Supply seems to be reasonable. To meet new requirements following changes should be applied:

• 12V input power filter is rated for 20A, but is only mislabeled, so it can be kept
• wider power planes, multiplied in different layers wherever possible should be applied
• Instead of TPS259573DSGR (IC47) solution rated for 20A should be applied.
• P3V3EEM enabling sequence should be considered

The last one could be resolved by two approaches:

• One circuit like TPS259830O if there will be enough space on PCB
• smaller switches for every particular EEM or group of EEM slots that will be enabled in daisy chain - in this case reverse current protection have to be applied to prevent unbalancing during start up

Any remarks will be kindly seen.

@gkasprow @marmeladapk @linuswck

[sbourdeauducq]

What about the DC jack? I don't think it'll be happy with 20A.

[linuswck]

I think the source of the 12V 5A max input power in the Power Supply Calculation comes from the DC Jack (P/N: 712RA) being rated for 5A only.

I agree that

• Power Jack should be changed to one with higher current rating
• Power budget of EEM Connector should be increased as well. 12V 18A is Okay.
• Adding individual power switch for each channel is a good solution if costs and PCB spaces allow.
• TPS259830O is good enough for this job(soft starting all EEM peripherals)

[martafafara]

DC Jack would change its role into fuse when 20A applied.
To keep the functionality some assumptions have to be done:

• full power is provided only by back side Molex connector and only this case allows to power up EEM cards
• if front panel connector used, the power is consumed only for controller
  If front panel DC Jack is connected, the EEM cards power up switch have to be disabled.

[linuswck]

I know DC Jack won't able to handle 20A. But, higher current rating is appreciated. We find the DC Jack current limit to be too low in some crate setup(ie. with Shuttler, with some other RF generator cards like phaser & mirny installed)

So, you mean you wanna separate the power path between Controller and EEM Peripherals?

1. DC Jack -> Controller
2. Rear Molex Connector -> Controller + EEM Peripherals

Using the DC Jack as the power source for both Controller + EEM Peripherals should be a very common use case IMO. How about adding a switch or jumper resistor pads/ solder jumpers to allow DC Jack power flowing to the EEM Connectors?

[martafafara]

You've understood my idea.

Instead of jumpers or switch I thought about using EN pin of TPS259830O to disable passing 12V to EEM connectors when DC Jack plugged. The alternate solution could be switching Rlim resitors depending on used connector.

[linuswck]

Where is the TPS259830O placed in the power path?

When DC Jack power is applied:

If front panel DC Jack is connected, the EEM cards power up switch have to be disabled.

When Molex power is applied:

full power is provided only by back side Molex connector and only this case allows to power up EEM cards

[martafafara]

I assumed that full power default mode will look like this:

When DC Jack used:

Alternatively using Rlim: