Mp3378e Protection Pin Upd Jun 2026

Check the buck converter side of the IC for shorts on the internal 144mΩ power MOSFETs. Deactivating the Protection Latch for Diagnosis

If your monitor backlight flashes and immediately turns off (or doesn't turn on at all), the MP3378E is likely entering protection mode. 1. Identify the Faulted Pin/String

: The IC monitors individual LED strings. If a string is detected as open or shorted, it can disable that specific string while keeping others active, or shut down depending on the severity. Thermal Protection

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. mp3378e protection pin upd

: By placing a temporary parallel resistor over the lower leg of the OVP voltage divider, the voltage sensed by Pin 9 is kept safely below the trigger threshold.

A working channel will have a low voltage (roughly 0.5V–1V). A channel with an open string will show close to the Boost voltage, while a shorted channel will show near 0V. 2. Monitor the OVP Pin

Measure the voltage on the LED current sink pins (usually labeled LED1–LED4) while turning the set on. Check the buck converter side of the IC

The OVP lower resistor (10kΩ) had a hairline crack, measuring 10.8kΩ. Recalculated V_PROT: Target 1.25V, actual 1.17V (due to 8% increase). This 0.08V difference fell into UPD zone.

If the backlight flashes and then turns off, the IC has likely detected a fault (e.g., an open LED string) and triggered its internal protection.

The most common application. Place an NTC thermistor from UPD to GND, with a pull-up resistor to the internal 5V. Identify the Faulted Pin/String : The IC monitors

This often indicates the OVP is triggering. Check if an LED string is disconnected or if your OVP resistor divider is set too low for the required output voltage.

If the LEDs fail short, the VLED pin sees an instant surge in voltage. The IC pulls that channel out of operation to protect against cascading thermal destruction. 3. Over-Current Sense (ISENSE)