Vicor VI Chip PRM Evaluation Board - Manual (Page 20)

UG:013 vicorpower.com Applications Engineering: 800 927.9474 Page 20
Default / Adaptive Loop operating mode using PRM ®
Mode select switch S10 setting: keep the switch OFF at all positions as shown in
following illustration. Please note that switch S10 is 10 positions switch.
In default operation, PRM maintains its own output voltage using active internal voltage
sensing. Also internal current sensing circuit is active for constant current limit. In
Adaptive Loop Operation, AL control programs the load line to compensate resistive
drops from the PRM output voltage to point of Load. Trim control sets the output voltage
other than the default 48 V in the range of 20 V to 55 V.
Default/Adaptive Loop controls
Trim control: Jumper and header select either external trim, trim POT, Trim to SGND
option or none. Place jumper across correct position in P11 to enable trim control.
Please note that R38 – 1206 resistor footprint is not populated in trim control. Instead,
External trim provides option to select sockets for easy installation of fixed resistor or
surface mount test points to apply external voltage source.
Trim control provides the option to select the potentiometer R40 using proper jumper
setting on header P11 in default / Adaptive Loop Operation. Rotate POT R40 clockwise
to increase the TRIM pin voltage and counterclockwise to decrease the TRIM pin voltage.
Trim control allows setting the TRIM pin voltage in the range of 1 V to 2.75 V to set the
output voltage between 20 V and 55 V.
Adaptive Loop control: Jumper and header select either external AL, AL POT, AL to
SGND option or none. Place jumper across correct position in P13 to enable AL control.
Please note that R37 – 1206 resistor footprint is not populated in AL control. Instead,
External AL provides option to select sockets for easy installation of fixed resistor or
surface mount test points to apply external voltage source.
AL control provides the option to select potentiometer R39 using proper jumper
setting on header P10. Rotate POT R39 clockwise to increase the AL pin voltage and
counterclockwise to decrease the AL pin voltage. AL control allows setting the AL pin
voltage in the range of 0 V to 3 V to program the PRM load line for
Adaptive Loop Operation.
1 2
3 4
5 6
P11
CN6_DIGIKEY_95278
TRIM
SGND
TP40
TP42
0603
R35
H50
H54
R40 1206
R38
TP70
TP69 TP71 TP72
TRIM CONTROL SELECT
EXT TRIM
TRIM POT
SGND
Figure 11.
Trim control selection
DEFAULT / ADAPTIVE LOOP
ON
OFF
1 2 3 4 5 6 7 8 9 10
Postion
number