Mp3378e Protection Pin Upd [ 2025-2027 ]

Not a separate pin – UPD refers to the ability to disable the input UVLO (Under-Voltage Lockout) via register or external logic on MP3378E (depending on variant).
In practice:

Used in battery-powered systems where deep discharge operation is needed, but output regulation may suffer.

With same timebase, monitor VOUT (boost output) and PROT pin together. mp3378e protection pin upd

Symptom: 15.6” 4K LCD panel, MP3378E-based backlight driver. LCD image visible with flashlight test, but backlight entirely off.

Diagnosis: PROT pin oscillated at 1.0V–1.3V at 2Hz. VOUT pulsed to 42V (target 48V), then dropped to 0V. No channel current. Not a separate pin – UPD refers to

Findings: 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.

Fix: Replaced both divider resistors with 0.1% parts (124kΩ upper / 5.23kΩ lower for 48V output). PROT pin locked at 1.25V, backlight restored. With same timebase, monitor VOUT (boost output) and

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