鈩?/div>
converter. The RSL resistor shown in Figure 4 of the
product datasheet (not on the evaluation board) can be
used to limit the correction current sourced from the
Adjust+ circuit if needed during start-up preventing the
converter from tripping OVP.
RHR is the headroom voltage setting resistor that will
determine the voltage dropped across the QPO-2. The
RSA1 resistor is for the slope-adjust option, which can be
used to reduce the amount of voltage across the QPO-2
depending on load current. This reduced drop in voltage
will result in a lower power loss across the QPO-2
providing greater efficiency but lower attenuation. An
optional capacitor, CHR, can be added to extend the low-
frequency attenuation range of the QPO-2.
The RP resistor connects the QPO-2鈥檚 peak detection circuit
to the input voltage rail. The peak detector will adapt the
headroom voltage by adding half the peak-to-peak ripple
voltage to the headroom. RP is required. The peak
detection can be disabled adding a filter capacitor CP to
the board. The full product datasheet with equations to
calculate these component values plus more detailed
explanations of their functions, can be found at
www.picorpower.com.
Evaluation Board for QPO-2 Active Output Filter
The QPO-2-EVAL1 board provides an easy to use
evaluation platform for testing the QPO-2L in a low-
voltage system. A filtered voltage range of 0.3 Vdc to 5.5
Vdc at output load currents up to 20A can be
accomplished. A low current bias supply is required at the
VAUX input in the range of 7 to 12 volts respectively to
the output voltage range. The board comes with a QPO-2L
and some essential external components pre-mounted.
Please refer to the QPO- 2L datasheet for product details.
Terminals for horizontal or vertical mounting are also
provided. The user must select component values
dependant upon their system needs.
RCP will preset the QPO-2鈥檚 reference voltage to a value
close to the desired steady-state value. This reduces the
time required for the QPO-2鈥檚 output to reach the
steadystate output voltage. There is a provision for a start-
up circuit (Q1 RDLY D1 CDLY) if the initial headroom
voltage needs to start from zero and increase gradually to
the set headroom voltage. Remote sense components (CRS
RRS), Figure 3 of the product datasheet, are mounted on
the evaluation board.
When remote sensing is not used RSC1 is the current
programming resistor that determines the current sourced
by the QPO-2鈥檚 Adjust+ pin to drive the TRIM pin of a
QPO_IN
J2
VAUX
QPO_OUT
J6
QPO_IN
RP
RCP
10 9
RCP/RON
Low Voltage Start-up Circuit
QPO_IN
CRS
15 渭F
J7
SENSE+
RRS
10
QPO_OUT
D1
MA111
CDLY
0.1 渭F
Q1
IRLML6401
J5
GND
VREF
J9
GND
J10
GND
RDLY
20 K
J5
ADJUST/SC
CP
PEAKIN
ADJUST
VAUX
11
12
13
14
18
QPO IN
QPO IN
QPO IN
QPO IN
QPO IN
QPO OUT
QPO OUT
QPO OUT
QPO OUT
SC SET
17
8
7
6
5
RSC1
J1
QPO_OUT
15 PEAK IN
SLOPE ADJ
16 ADJUST+/-
GND
19 GND
20 GND
REFGND
QPO-2
1
2
VREF
3
4
RSA 1
RHR
VREF
CHR
J3
VREF
Figure 1
- Evaluation board schematic
Picor Corporation 鈥?www.picorpower.com
QPO-2 EVAL1 Data Sheet Rev. 1
Page 1 of 2
VICOR
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