The regulator toggles a MOSFET (internal to U1) at 500 kHz–1 MHz, storing energy in L1. The output voltage is regulated via the R1‑R2 divider. R3 senses the boost‑stage current, feeding back to the internal over‑current protection.
The LA-D401P is built around the platform, depending on the specific revision. Key components identified in the schematic include: la-d401p schematic
| Symptom | Likely Cause | Diagnostic Steps | |---------|--------------|-------------------| | | Power not reaching board (blown fuse, broken J1) | Check continuity of J1 → F1 → D1; measure voltage after F1 | | LED flashes red | Over‑current or over‑temperature protection active | Measure voltage across R7 (over‑current) and TMP1 (temperature). Replace Q1 if it shows high Rds(on). | | Output voltage present but current low | Sense resistor R4 drifted high, or U2 lost offset | Measure voltage across R4 at a known load; replace R4 if > spec | | Oscillating output | Insufficient compensation (C4 too low) or poor layout (long gate trace) | Add small parallel capacitance (e.g., 4.7 nF) to the gate of Q1, shorten trace | | Excessive heat on board | Boost inductor saturated or MOSFET overloaded | Verify L1 inductance and current rating; check Q1 for overheating (use thermal camera) | The regulator toggles a MOSFET (internal to U1)
The regulator toggles a MOSFET (internal to U1) at 500 kHz–1 MHz, storing energy in L1. The output voltage is regulated via the R1‑R2 divider. R3 senses the boost‑stage current, feeding back to the internal over‑current protection.
The LA-D401P is built around the platform, depending on the specific revision. Key components identified in the schematic include:
| Symptom | Likely Cause | Diagnostic Steps | |---------|--------------|-------------------| | | Power not reaching board (blown fuse, broken J1) | Check continuity of J1 → F1 → D1; measure voltage after F1 | | LED flashes red | Over‑current or over‑temperature protection active | Measure voltage across R7 (over‑current) and TMP1 (temperature). Replace Q1 if it shows high Rds(on). | | Output voltage present but current low | Sense resistor R4 drifted high, or U2 lost offset | Measure voltage across R4 at a known load; replace R4 if > spec | | Oscillating output | Insufficient compensation (C4 too low) or poor layout (long gate trace) | Add small parallel capacitance (e.g., 4.7 nF) to the gate of Q1, shorten trace | | Excessive heat on board | Boost inductor saturated or MOSFET overloaded | Verify L1 inductance and current rating; check Q1 for overheating (use thermal camera) |