Vicor Constant Current (CC) Demonstration Board - Manual (Page 4)

UG:007 vicorpower.com Applications Engineering: 800 927.9474 Page 4
2.1.2 CC Demonstration Board Components
1. Input capacitors (C01, C02, C03): A 22 µF capacitance assuming a low input source
impedance.
2. Fast-acting fuse (F01): Rated for 10 A.
3. Potentiometer V
REF
(R10): Provides an adjustable voltage divider in combination with (R6).
This divider achieves the reference voltage used to set the value of the PRM output
current. Please refer to the application note
AN: 018 Providing a Constant Current for
Powering LEDs using the PRM and VTM for more details on start up sequencing precautions.
4. Potentiometer V
MAX
(R8): Combined with (R27) V
MAX
make up the OS resistor referred
to in the PRM datasheet . The OS resistor is used to set the output voltage of the PRM.
In this case it is used to limit the PRM maximum output voltage the CC feedback can drive
in order to source more current.
5. Dual op amp (U02): U02A shown in Figure 1 is used as a difference amplifier sensing the
voltage produced by the current flowing though the PRM output sense resistor (R33).
Op amp (U02B) regulates the output of op amp (U02A) against the manually set reference
using the potentiometer (R10) or an external shunt regulator.
6. Output inductor (L01): The PRM soft switches at a frequency greater than 1 MHz while the
VTM soft switches at a frequency of 1.7 MHz. L01 is used to reduce the high frequency
current ripple produced by the high frequency switching inside the PRM.
7. Sense resistor (R33): The voltage across the sense resistor is captured by the difference
amplifier then fed back to the PRM SC pin through the error amplifier in order to maintain
the current regulation. R33 is a 1 w, ±0.1% tolerance, 10 m
Ω high precision metal strip
current sense resistor positioned at the –OUT of the PRM.
8. PRM connection highlights:
Figure 4
PRM-AL Schematic Symbol
+Out
–Out
+In
–In
VC
PC
TM
IL
VH
PR
NC
SG
SC
PR M -A L
OS
NC
CD
Vout Vin