If you are dealing with a specific device failure, tell me you are repairing and what voltage readings you get on Pin 9. I can provide targeted troubleshooting steps for your exact board layout. MP3378E - Monolithic Power Systems
| Pin Name | Pin # | Function & Protection Relevance | | :--- | :--- | :--- | | | 20 | Bootstrap for buck converter high-side driver. Critical for gate drive; must be monitored for UVLO condition. | | SYNC | 21 | Synchronization input for buck converter. Connect external clock (250kHz-2MHz) to synchronize switching. | | ISENSE | 22 | Current sense input for WLED controller. Senses external inductor current for peak current-mode control and OCP detection. | | GATE | 23 | Power switch gate output for WLED controller. Drives external N-channel MOSFET; OCP detection involves monitoring gate drive. | | VIN1 | 24 | Supply input for WLED controller. Monitored for UVP. | | VCC1 | 25 | Internal 6V linear regulator output for WLED controller. Supplies external MOSFET driver and internal circuitry; bypass to GND. | | COMP | 26 | Error amplifier output for WLED controller. Used for loop compensation; COMP voltage clamping used in inductor/diode short protection. | | EN1 | 27 | Enable input for WLED controller. Pull high to enable; logic-level control for startup/shutdown. | | PWM | 28 | PWM brightness control input. Used for dimming only; not for enabling/disabling controller. | | LED1-4 | 14,13,12,11 | LED string current sense inputs. Monitor LEDX voltages for open/short string detection. | | OVP | 8 | Over-voltage protection sense input. Set OVP threshold via external resistor divider. | | FB | 9 | Feedback for buck converter. Used for output voltage regulation and OVP detection. | | EN2 | 10 | Enable input for buck converter. Pull high to enable; shutdown controlled by EN2, VIN2 UVLO, or thermal shutdown. | | VIN2 | 18,19 | Supply input for buck converter. Monitored for UVLO. | | SW | 20 | Switching node for buck converter. High-dv/dt node; keep away from sensitive analog areas. | | AGND | 21 | Analog ground reference for buck converter. Connect single-point to GND1. | | VCC2 | 22 | Internal 5V regulator output for buck converter. | | GND2 | 23,24 | Power ground for buck converter. | | ADIM | 16 | Analog dimming control. Supports PWM or DC signal for LED current adjustment. | mp3378e protection pin upd