QPO-2-EVAL1 Vicor

VAUX USER GUIDE | UG:314 QPO-2-EVAL1 QPO Active Output Filter Evaluation Board 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 5.5V at output load currents up to 20A can DC be accomplished. A low current bias supply is required at the VAUX input in the range of 7 12V 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 data sheet 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-2s reference voltage to a value close to the desired steady-state value. This reduces the time required for the QPO-2s output to reach the steady-state 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) shown in Figure 3 of the product data sheet 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-2s ADJUST+ pin to drive the TRIM pin of a converter. The RSL resistor shown in Figure 4 of the product data sheet (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-2s 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 0.1F capacitor on its peak detector pin that allows the user to filter out the converters 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 0 that comes pre-installed on the QPO-2 Eval board. J1 QPO_IN Figure 1 VAUX QPO_OUT Evaluation board schematic J6 RCP QPOIN J7 RP QPOIN 10 9 0 Low voltage start-up circuit 11 17 QPO_OUT J2 QPO IN QPO OUT QPOOUT 12 8 QPO IN QPO OUT 13 7 QPO_IN QPO IN QPO OUT 14 6 J3 QPO IN QPO OUT QPOOUT 18 QPO IN RDLY SCSET CRS 20K PEAKIN 15 5 15F PEAK IN SC SET D1 J5 RSC ADJUST 16 ADJUST/SC ADJUST+/- J8 Q1 SENSE+ 19 MA111 GND IRLML6401 20 GND CDLY RRS 0.1F 51.1 J4 GND 1 2 3 4 QPO_OUT V J9 REF GND J10 RSA GND RHR CHR V REF UG:314 Page 1 GND SLOPE ADJ RCP/RDN VREF/RUP VAUX REFGNDFigure 2 Evaluation board layout Note: Components Q1, D1, RDLY and CDLY are for an optional start-up circuit Ordering Information Part Number Description QPO-2-EVAL1 Evaluation board for QPO-2LZ UG:314 Page 2