: A high-efficiency step-down component providing internal bus voltage and standby power.
The does not have a single pin labeled specifically as "protection"; instead, its comprehensive protection suite is spread across several specialized pins including OVP , ISET , ISENSE , and LED1–4 .
The OVP pin is a dedicated input that monitors the output voltage of the step-up converter to prevent catastrophic failures. mp3378e protection pin upd
MP3378E Protection Pin UTP/OVP/UVP: Understanding and Troubleshooting the MP3378E Protection Pins
MP3378E Protection Pin UPD: Deep Dive Guide to Over-Voltage Protection (OVP) and Backlight Diagnostics Benefits : Prevents damage to LED strings and
| Protection Type | Detection Method | Fault Response & Thresholds | Critical Pins | | :--- | :--- | :--- | :--- | | | Monitors the boosted output voltage | Event : Output exceeds programmable OVP threshold set by resistor divider on OVP pin. Response : Controller stops switching and latches off until reset. Trigger after fault persists for 4μs. Benefits : Prevents damage to LED strings and external MOSFET from excessive voltage. | OVP, VOUT | | Under-Voltage Protection (UVP) | Monitors VIN1 and VCC1 internal regulator | Event : Input voltage or internal 6V regulator drops below threshold. Response : Entire WLED controller shuts down until voltage recovers. Benefits : Prevents erratic operation from insufficient supply voltage. | VIN1, VCC1 | | Over-Current Protection (OCP) | Senses current via external sense resistor (R_SENSE) on ISENSE pin | Event : Inductor current exceeds current limit. Response : Stops switching; after 512 switching cycles of clamped COMP voltage, controller turns off and latches. Benefits : Protects external MOSFET and inductor from excessive currents. | ISENSE, COMP, GATE | | Over-Temperature Protection (OTP) | Monitors silicon die temperature via internal sensor | Event : Junction temperature > 150°C (typical). Response : Controller shuts down when exceeding upper threshold; returns to normal operation when temperature drops below lower threshold (recoverable). Hysteresis ~ 20°C. Benefits : Prevents thermal damage under high ambient temperature or heavy load conditions. | Internal | | LED Open-String Protection | Monitors LEDX (pin 14, 13, 12, 11) voltages per string | Event : Any string voltage below 190mV indicates open LED string. Response : Controller marks off faulty string; remaining strings regulate normally. If all strings open, controller shuts down until reset. Benefits : Allows continuous backlighting with remaining strings while protecting against open-circuit failures. | LED1, LED2, LED3, LED4 | | LED Short-String Protection | Monitors LEDX voltage exceeding 6.3V | Event : LEDX voltage > 6.3V for 4096 switching cycles. Response : Fault string marked off and disabled; disconnected from output voltage loop. Marked strings shut off completely until boost part restarts. Note : Protection disabled when all used channels have VLEDX > 1.5V to prevent mistriggering. | LED1, LED2, LED3, LED4, ADIM | | Inductor/Diode Short Protection | Dual detection: COMP voltage clamping and MOSFET current sensing | Method 1 : COMP voltage clamped high for 512 switching cycles. Method 2 : Current sense voltage across R_SENSE hits VLMT limit for 4 switching cycles. Response : Controller turns off and latches in both cases. Benefits : Critical for preventing catastrophic damage when external inductor or diode fails short. | COMP, ISENSE, GATE | | Bootstrap UVLO Protection | Monitors BST-SW voltage differential for floating driver | Event : BST-SW voltage < 2.2V. Response : Disables high-side MOSFET driver, preventing shoot-through. Typical hysteresis of 150mV. Benefits : Ensures sufficient gate drive voltage for external power MOSFET. | BST, SW |
When servicing modern display panels, repair technicians frequently encounter a problematic symptom: the TV or monitor displays a brief splash screen (the logo flashes once) and then immediately goes black, while the power indicator LED blinks continuously. This issue is almost always triggered by the due to a minor shift in LED string impedances or localized component aging. Response : Disables high-side MOSFET driver
They monitor the cathode voltage of each LED string.
Cycle-by-cycle over-current protection for the external MOSFET.
: These pins monitor the voltage on each LED string.