These pins monitor the current through the external MOSFET and the LED strings. If an inductor or diode shorts out, or if the current exceeds the limit set by the current-setting resistor, the IC immediately disables the driver to protect the internal circuitry and external components from melting. Critical Thresholds and Parameters
Use ≥ 22nF for most 12V→40V applications. Do not use < 10nF.
: Runs at a fixed 235kHz but supports external clock synchronization ranging from 250kHz to 2MHz.
For detailed electrical specifications and circuit diagrams, you can refer to the MP3378E Datasheet provided by Mouser Electronics . MP3378E - Mouser Electronics mp3378e protection pin upd
: If severe damage short-circuits several LEDs in a string, the voltage on that specific LED pin surges. If it exceeds the internal short-circuit limit, the chip shuts down the damaged channel to prevent severe overheating. 3. The ISENSE / COMP Pin Mechanics
These pins monitor the current in each LED string. If a string is open or shorted, the voltage at these pins will trigger a fault protection.
The table below summarizes the key pins relevant to protection features and fault management. Refer to the official datasheet for full pin details. These pins monitor the current through the external
: Features a simplified protection loop consisting of localized Over-Current Protection (utilizing Hiccup mode) and thermal shutdown safeguards.
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:
On the MP3378E, the protection pin (commonly labeled “PROT”, “PGOOD”, “FAULT”, or similar in regulator datasheets—hereafter “PROT”) provides a compact interface for the chip’s internal safety features. The PROT pin typically performs one or more of the following roles: Do not use < 10nF
: Once the OVP pin voltage crosses the upper threshold, the IC instantly disables the switching gate driver to prevent catastrophic component failure. 2. LED1 through LED4 Pins (String Status Feedback)
Before altering any component configuration, technicians use a digital multimeter or an oscilloscope to monitor the voltage levels at the and the VLED channels during that brief power-up sequence. If the OVP pin spikes immediately to its shutdown limit, the issue is typically a broken load circuit or an open LED loop causing voltage to surge indefinitely. Stabilizing the Pin for Component Testing
To set the maximum allowable output voltage, select the upper ($R_OVP_UP$) and lower ($R_OVP_LOW$) divider resistors using the formula: $$V_OUT_MAX = V_OVP_TH \times \left(1 + \fracR_OVP_UPR_OVP_LOW\right)$$
This article unpacks what UPD means, how the protection pin works, why UPD triggers, and how to diagnose and resolve it.