Mp3378e Protection Pin | Upd
Under-Protection Detection (UPD) is triggered when the MP3378E detects a potential fault condition (e.g., rising output voltage or current mismatch) but the expected protection response (e.g., PWM dimming cycle termination or soft-start reset) does not occur within a predefined timing window. In essence, UPD indicates that the protection pin is receiving a fault signal under the threshold for normal shutdown, creating an ambiguous logic condition.
Among these, UPD is the least documented but most frequently implicated in "stuck-off" conditions. mp3378e protection pin upd
Some designs allow the host controller to read the PROT pin via an ADC. If UPD is persistent but the backlight is functional at reduced brightness, implement: System disable:
The MP3378 uses dedicated LED1 through LED8 pins to regulate the current. These pins serve a dual purpose: current regulation and fault detection. Latching fault handling:
Open String Protection (Single String): If an entire LED string becomes open-circuit (broken PCB trace or broken LED), the voltage at the corresponding LED pin drops to zero (or very low). Since the current source cannot regulate current, the boost converter will increase $V_OUT$ to compensate.
Open String Protection (All Strings): If all strings are open (e.g., the display connector is unplugged), the boost converter will ramp up voltage rapidly. The OVP pin triggers immediately to shut down the converter, preventing voltage explosion.
Inside the MP3378E, the UPD pin has: