The from Monolithic Power Systems (MPS) is a highly integrated 4-channel WLED controller, frequently used in LED monitors, laptops, and LCD television backlights. While known for its efficiency and compact design (TSSOP-28 EP package), it is a sophisticated IC that relies heavily on its protection pins to ensure safety and prevent hardware damage.
Switching regulators must deliver stable output voltages while protecting themselves and the load from abnormal conditions such as short circuits, overcurrent, thermal stress, and output overvoltage. Dedicated protection pins provide hardware-level interfaces that expose these protection functions to system designers, enabling predictable interactions between the regulator and the rest of the system (for example, enabling external shutdown, signaling fault status to a microcontroller, or allowing configuration of threshold/response behavior).
The MP3378E has 4 strings. If one string is open or shorted, the IC will shut down. mp3378e protection pin upd
During bench testing, engineers can stabilize or calibrate the protection threshold of the monitoring system using specific passive components.
If one string is damaged, you can sometimes connect the faulty string's input to a functional channel (via a resistor), effectively tricking the IC into thinking all 4 strings are active. Summary of MP3378E Features 4-String WLED Controller: Max 350 mA/string. External MOSFET Drive: Drives boost converter. Input Range: Up to 24 V. Dimming: Supports both analog and PWM dimming. Package: Available in SOIC28 and TSSOP28EP. The from Monolithic Power Systems (MPS) is a
Forces a recoverable shutdown if the internal junction temperature exceeds safety thresholds. Pin Layout and Hardware Implementation
: This is a primary safeguard for the boost converter. The MP3378E constantly monitors the output voltage of the boost converter (VOUT). If this voltage exceeds a programmable threshold set by a resistor divider, the controller immediately shuts down the power switch to prevent damage to downstream components like the LED strings and output capacitors. This protection acts as a fast-response circuit breaker, tripping before high voltage can cause catastrophic failure. It also performs a pre-startup check for short circuits or improper connections. During bench testing, engineers can stabilize or calibrate
If the backlight flashes and then turns off, the IC has likely detected a fault (e.g., an open LED string) and triggered its internal protection.
The MP3378E features an exposed thermal pad underneath the HTSSOP-28 package. If the solder joint on this pad cracks due to thermal cycling, the IC will experience rapid thermal blooming, triggering the internal recoverable thermal shutdown within seconds of power-up.
: Placing a 100nF ceramic capacitor (typically an X7R dielectric rated for 16V) in parallel with the grounding resistor acts as a low-pass filter. This prevents high-frequency electromagnetic interference (EMI) from inducing a false over-voltage shutdown signal on the sensitive internal comparators. Risks of Permanent Protection Modification