MP1584 Buck Converter
Adjustable 4.5–28 V in, 0.8–20 V out switching regulator with output filter.
Difficulty: Surface-mount. Estimated build time: about 90 minutes. Estimated parts cost: about US$4.00. 11-line bill of materials. Compare supplier offers when available. A compact switching buck converter built around the MP1584EN in SOIC-8 with exposed pad.
Solder the MP1584EN
The SOIC-8E package has an exposed thermal pad on the bottom. Solder the pad first with a hot-air station or by applying heat from the side to reflow paste under the pad—this is the main thermal path. Then solder the eight signal pins. Inspect for bridges; pin pitch is 1.27 mm. Poor thermal pad contact causes the IC to throttle under load.
Place input capacitors and inductor
Solder the input bulk capacitor (47 µF electrolytic, 35 V or higher) and a 100 nF ceramic input bypass capacitor close to the VIN and GND pins. Solder the switching inductor between the SW pin and the output rail. Use a 4.7–10 µH inductor rated for at least 3 A saturation current at your target switching frequency (set by the FREQ resistor; 68.1 kΩ gives roughly 500 kHz).
Output filter and feedback divider
Solder the output bulk capacitor (47 µF, low-ESR electrolytic or ceramic) and a 100 nF ceramic in parallel between VOUT and GND. Set the output voltage with two resistors from VOUT to FB and from FB to GND. For 5 V output: R_top = 200 kΩ, R_bot = 39.2 kΩ gives VOUT = 0.8 × (1 + 200k/39.2k) ≈ 4.98 V. Use 1% tolerance resistors.
Bootstrap and enable
Connect a 100 nF bootstrap capacitor between the BST and SW pins—this charges from the output to bias the internal high-side gate driver. Tie the EN pin to VIN through a 100 kΩ resistor (or directly to VIN) to enable the converter at power-up. Leaving EN floating can cause undefined startup behavior.
Test under load
Apply input voltage and measure VOUT with no load first. Verify it matches the calculated value. Then apply a load (resistive, starting at ~100 mA) and confirm regulation. Check the IC temperature after 60 seconds at full load—warm is expected, hot-to-touch suggests inadequate thermal pad soldering or insufficient input voltage headroom.