Mp3378e - Protection Pin Upd

Connect an open-drain/collector transistor or mechanical switch between UPD and GND. When activated, it pulls UPD low → immediate latch-off.

The MP3378E uses a resistor divider from VOUT (boost output) to the PROT pin. If the divider is incorrectly calculated or damaged:

The MP3378E monitors each channel’s current via external sense resistors (RISET). If one channel has a significantly different resistor value (e.g., a wrong part or cold solder joint), the internal current balancing algorithm creates a persistent “under-protection” condition.

The MP3378E includes comprehensive protection mechanisms that monitor various conditions to prevent hardware failure: LED Protection : Detects and responds to both mp3378e protection pin upd

Guards the boost circuit components . Handling Protection Pins for Repair

Before concluding that the MP3378E IC itself is defective, use a standard diagnostic sequence to isolate the actual failure point:

Use a resistor divider between the boost output and ground. Calculate the resistors so that the OVP pin reaches ~1.2V only when the output is at its maximum safe limit. If the divider is incorrectly calculated or damaged:

Detects faults in individual LED strings .

that combines a 4-channel WLED controller with a high-efficiency buck converter, primarily used in monitor applications. MPS | Monolithic Power Systems

Bypassing protection can cause permanent damage to the LEDs or the driver if an actual short circuit exists . Current Adjustment: Handling Protection Pins for Repair Before concluding that

These pins monitor the current and residual voltage across each LED string. If a channel drops to near-zero volts (LED shorted) or spikes abnormally (LED open), the IC identifies an imbalance and cuts power to protect the panel from uneven thermal dissipation. Step-by-Step Diagnostic and Modification Guide (UPD)

: Leveraging the buck converter's OCP to ensure that even if the backlight fails, the internal standby power remains stable for diagnostic reporting to the main system processor. MPS | Monolithic Power Systems

The following protection functions and their corresponding pins/mechanisms are detailed in the MP3378E technical documentation :

: With the protection circuit temporarily desensitized, the board can stay powered on for a few additional seconds. This short window allows the technician to read exact operating currents across LED1–LED4 using an oscilloscope or modern multimeter.

Set oscilloscope to 2V/div, 20ms/div. Trigger on rising edge of EN (enable) signal. Capture PROT pin voltage.