QPO-2-EVAL1

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 – 5.5VDC 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 – 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-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 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-2’s 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-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 0.1µF 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 0Ω that comes pre-installed on the QPO-2 Eval board. J1 VAUX QPO_IN J6 QPO–IN RP 0 11 12 13 14 18 J4 GND VREF ADJUST 15 PEAK IN 16 ADJUST+/19 GND 20 GND 1 SC SET 5 REFGND QPO_OUT CDLY 0.1µF PEAKIN 17 8 7 6 SLOPE ADJ MA111 RRS 51.1 Q1 IRLML6401 J5 ADJUST/SC QPO OUT QPO OUT QPO OUT QPO OUT VREF/RUP J8 SENSE+ D1 RDLY 20K QPO IN QPO IN QPO IN QPO IN QPO IN GND QPO_IN RCP/RDN 10 9 Low voltage start-up circuit CRS 15µF QPO_OUT VAUX J7 QPO–IN RCP VAUX Figure 1 Evaluation board schematic 2 3 4 QPO_OUT J2 QPO–OUT J3 QPO–OUT SCSET RSC J9 GND J10 GND RSA RHR CHR VREF UG:314 Page 1 Figure 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 Limitation of Warranties Information in this document is believed to be accurate and reliable. HOWEVER, THIS INFORMATION IS PROVIDED “AS IS” AND WITHOUT ANY WARRANTIES, EXPRESSED OR IMPLIED, AS TO THE ACCURACY OR COMPLETENESS OF SUCH INFORMATION. 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