If you encounter a non-functional backlight with UPD suspected, follow this systematic diagnostic flow.
Disconnect the LED+ and LED- cables from the driver board. Replace with a dummy load (e.g., 1kО© resistor from SW to GND and a 47kО© from VOUT to GND). This removes actual LEDs from the equation.
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: mp3378e protection pin upd
VIN < VIN_UVLO (typ 4.5V).Used in battery-powered systems where deep discharge operation is needed, but output regulation may suffer.
Connect an open-drain/collector transistor or mechanical switch between UPD and GND. When activated, it pulls UPD low в†’ immediate latch-off. Decoding the MP3378E Protection Pin: A Deep Dive
The MP3378E is designed for safety-critical LED backlights (e.g., automotive, industrial). A latched response ensures that once a fault occurs (e.g., overheating, overvoltage), the system does not auto-retry, preventing potential fire or damage from repeated stress. The system requires an explicit reset (power cycle or EN toggle), forcing an external diagnostic check.
The MP3378 is a boost controller designed to drive up to 8 parallel strings of white LEDs. To ensure system reliability and protect both the driver IC and the LED load, the device incorporates several protection mechanisms. These protections are primarily configured and monitored through specific pins: OVP (Over-Voltage Protection), PROG/OC (Current Setting/Protection), and the LEDx (String Fault) pins. The pin is left open or pulled high via an external resistor
Check if the PROT pin trace runs parallel to the SW (switching) node for more than 5mm. Switching spikes (up to 50V/ns) can couple into the PROT pin, causing false UPD. A 100pF capacitor from PROT to GND near the IC often resolves this.