Picor Corporation • www.picorpower.com QPO-2-EVAL1 Data Sheet Rev. 1.2 Page 1 of 2
The QPO-2-EVAL1 board provides an easy to use
evaluation platform for testing the QPO-2 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-2LZ
and some essential external components pre-mounted.
Please refer to the QPO- 2 datasheet for product details.
Terminals for horizontal or vertical mounting are also
provided. The user must mount and select component
values for RHR, RSC, RSL and RSA based on their system needs.
RCP will preset the QPO-2’s reference voltage to a value
close to the desired steady-state value. This reduces the
time required for the QPO-2’s 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 RSC is the current
programming resistor that determines the current sourced
by the QPO-2’s Adjust+ pin to drive the TRIM pin of a
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 RSA
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’s 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. Internally, the QPO-2 has a
0.1uF capacitor on its peak detector pin that allows the
user to filter out the converter’s ripple with an
appropriate RP resistor value, disabling the peak detector.
This filtering is enabled by using a low resistance value for
RP, such as a zero ohm that comes pre-installed on the
QPO-2 Eval board.
