Setting Vout for an SMPS power module?

Hello This SMPS module appears to have a settable output voltage via its “REF” pin which enables the user to set a voltage at the error amplifier reference input.

However, when "Adaptive loop” mode is set, the datasheet says not to use the “REF” pin. Why is this? Why can we not use the REF pin to set the Vout?
MPRM48NH480M250A00 SMPS module datasheet:-
https://www.vicorpower.com/documents/datasheets/MPRM48NH480M250A00_ds.pdf

Hi,

You should use the TRIM pin to set the output in adaptive loop mode (pages 28 and 30)

RS

thanks, in adaptive mode, do you assume its always going to be stable, with good phase and gain margin, as long as you use the indicated amount and type of output capacitance?

You can assume normal and stable operation as long as you follow the DS recommendations, it works in my designs...

RS

Thanks, this next post concerns the same power modules, please may i put it here...

Hello,
We are converting 48v to 1.5v with a cascade of A vicor PRM module and a VTM module as on top of page 2 of the datasheet below.

What is the VC pin for on the PRM module?....its a waste of time, the VTM doesn’t need a signal from the VC to get started?
Vicor PRM module datasheet
http://cdn.vicorpower.com/documents/datasheets/PRM48BH480T250A00_ds.pdf

The next post here considers the same power modules, so any help with this question much appreciated also....
Hello,

We are doing a 48V to 1V5 power supply by way of a 48Vin to 48Vout “PRM” module feeding into an “electronic transformer” (Ns/Np = 1/32) module called a “VTM” module (datasheets of modules as below)

The output current is 95A at 1V5, and so even though the PRM module is regulated, the voltage at the actual output of the VTM module will actually reduce as the current gets higher…therefore, the PRM module has an “adaptive load” regulation feature whereby it increases its output voltage as the output current gets higher.

The adaptive loop mode requires one to set an “AL” resistor connected to the PRM module. This gives an “AL” pin voltage. However, the AL pin voltage has a maximum of 3.1V. Therefore, the maximum PCB trace resistance at the output of the VTM module that can be compensated for is just 3.027 milliohms….this is obviously not a lot. Can you confirm that the maximum is 3.027 milliohms as stated?

PRM48BH480x250A00 module datasheet:
http://cdn.vicorpower.com/documents/datasheets/PRM48BH480T250A00_ds.pdf

VTM48EF015T115A00 module datasheet:
http://cdn.vicorpower.com/documents/datasheets/VTM48E_015_115A00.pdf

treez said:

Thanks, this next post concerns the same power modules, please may i put it here...

Hello,
We are converting 48v to 1.5v with a cascade of A vicor PRM module and a VTM module as on top of page 2 of the datasheet below.

What is the VC pin for on the PRM module?....its a waste of time, the VTM doesn’t need a signal from the VC to get started?
Vicor PRM module datasheet
http://cdn.vicorpower.com/documents/datasheets/PRM48BH480T250A00_ds.pdf

Click to expand...

You do need to connect the Vc pin to VTM.
from VTM datasheet p.9:
"The VTM® Control (VC) pin is an input pin which powers the internal VCC circuitry when within the specified voltage range of 11.5 V to 16.5 V. This voltage is required for VTM current multiplier start up and must be applied as long as the input is below 26 V. In order to ensure a proper start, the slew rate of
the applied voltage must be within the specified range."

thanks, but we do not want the VTM module to operate when ints vin is below 26v

This next question concerns again the vicor power modules, please may i therefore put it here?...
We are doing a 48vin to 1V5, 95A power supply using a PRM module (48v to 48v) feeding into a “electronic transformer” module (VTM module).
Module datasheets are below.

We don’t want the VTM module to turn on when its Vin is less than 40V….therefore, can we leave its VC pin unconnected?

Also, we are using the PRM module in “adaptive loop” mode. So does the temperature compensation aspect of this come from the TM pin of the VTM module?...or does it also come from the VC pin of the VTM module?.........the VTM datasheet on page 3 says that the VC pin internal resistance is used in “adaptive loop” mode…..but if that’s the case then what does the TM pin do?

PRM48BH480x250A00 datasheet
http://cdn.vicorpower.com/documents/datasheets/PRM48BH480T250A00_ds.pdf

VTM48EF015T115A00 datasheet
http://cdn.vicorpower.com/documents/datasheets/VTM48E_015_115A00.pdf

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Hello, The following question concerns the same power modules as in the above questions, so may I place it here?...............
We are doing a 48vin to 1V5, 95A power supply using a PRM module (48v to 48v) feeding into a “electronic transformer” module (VTM module).
Module datasheets are below.

We want to increase the soft start time. Can we do this by adding an external capacitor to the PC pin? -Or does that just increase the start-up delay time?


PRM48BH480x250A00 datasheet
http://cdn.vicorpower.com/documents/datasheets/PRM48BH480T250A00_ds.pdf

VTM48EF015T115A00 datasheet
http://cdn.vicorpower.com/documents/datasheets/VTM48E_015_115A00.pdf