For detailed design-in support, refer to the official MP3378E datasheet and EV3378E-F-00A evaluation board documentation available from MPS.
Monitor it, respect its gray zones, and UPD will never blindside your next repair or prototype.
Automatically shuts down the chip if internal temperatures reach unsafe levels.
: Master enable pin for the WLED controller. 🔍 Understanding the Protection Mechanism
that combines a 4-channel WLED controller with a high-efficiency buck converter, primarily used in monitor applications. MPS | Monolithic Power Systems mp3378e protection pin upd
By understanding the voltage thresholds, timing windows, and external component interactions that lead to UPD, you can quickly resolve “dead backlight” faults and design more robust LED drivers. The key takeaway:
: If one LED string is disconnected, the voltage on the OVP pin will rise rapidly, triggering a shutdown.
Monitors the current through the inductor.
: If a string disconnects, its corresponding LEDX pin drops to ground. The IC attempts to compensate by ramping up the voltage until it trips the OVP threshold, subsequently shutting down or disabling the faulty channel. For detailed design-in support, refer to the official
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.
The confusion over a single pin likely stems from the MP3378E's robust set of internal safety features. Rather than a single pin, protection is distributed and monitored across various pins and internal circuitry, all designed to prevent damage to the IC and the LED strings it controls.
Technicians often check the voltage on this pin; if it exceeds the internal reference, the IC shuts down. In some ICs (like the related MP3398E), connecting a to ground can stabilize protection behaviors . Disabling Protection (For Diagnosis Only):
Monitors the voltage at each LED channel pin (LED1–LED4). : Master enable pin for the WLED controller
: While primarily for setting the LED current, this pin also detects faults. An open or shorted ISET resistor will trigger protection mechanisms to disable the WLED driver.
Calculate expected PROT voltage: V_PROT = VOUT * (R_lower / (R_upper + R_lower)) Compare with measured PROT pin voltage with EN low. A discrepancy >2% indicates leakage or damaged resistors.
When an LED backlight fails—either due to a burnt-out diode or a degraded solder joint—the MP3378E enters protection mode. This creates a common symptom known as the : The TV/monitor is powered on. The splash logo (e.g., Sony, Samsung) briefly appears.
If one or more of the 4 strings have a broken trace or failed diode, the corresponding LED pin (Pins 25–28) will read anomalously high or float to a flat zero before the shutdown occurs. 2. Checking Resistor Dividers
Ensure all LED strings have similar forward voltage drops. ISENSE Pin (Pin 22)