Monolithic Power Systems Inc. MP3309AGQ-P

Overview

MP3309AGQ-P from Monolithic Power Systems is a synchronous boost white LED driver IC designed for portable backlighting applications. It operates from 2.7V–5.5V input, delivers up to 35.5V output, regulates LED current via 200mV ±1% feedback voltage, supports both analog and PWM dimming, and features programmable switching frequency (300kHz–1.2MHz) for efficiency optimization in space-constrained designs like smartphones and tablets.

For engineers reviewing the MP3309AGQ-P datasheet, MP3309AGQ-P pinout, MP3309AGQ-P application, or MP3309AGQ-P equivalent, key selection criteria include its 3×3mm QFN10 package, dual-dimming interface (EN/PWML + PWMH), open-string OVP at 35.5V, cycle-by-cycle current limit (1.4A–1.8A), and thermal shutdown at 150°C - all critical for reliable WLED string control in battery-powered displays.

Technical Context

The MP3309AGQ-P employs peak-current-mode control with internal ramp compensation to ensure stability at duty cycles >50%. Its error amplifier compares 200mV reference against FB-sensed resistor voltage, driving PWM logic that controls an integrated low-side N-MOSFET (RDSON = 0.3Ω typ.) and synchronous high-side switch (RDSON = 0.5Ω typ.).

OVP protection triggers at 35.5V with 2.5V hysteresis, while startup includes soft-start with reduced 0.8A current limit for 5ms. Dimming is implemented via two independent paths: EN/PWML accepts 100Hz–2kHz PWM for on/off control, and dual PWMH pins accept >20kHz PWM for analog current scaling via internal RC filtering.

Key Specifications

Pinout & Package

MP3309AGQ-P is housed in a thermally enhanced 3×3mm QFN10 package with exposed thermal pad, optimized for compact portable PCB layouts and efficient heat dissipation in backlight driver applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar white LED driver applications.

Compared with MP3302DJ-LF-P and RT9397BZSP, MP3309AGQ-P uniquely combines programmable frequency, synchronous operation, and 35.5V OVP in a 3×3mm QFN10 - delivering superior efficiency, thermal performance, and design flexibility for modern portable displays.

Availability

MP3309AGQ-P is available at Aetrix Electronics and suitable for smartphone backlighting, tablet display drivers, portable media player displays, and industrial HMI panels requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for MP3309AGQ-P includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MP3309A belongs to MPS's WLED boost driver product line, engineered specifically for energy-efficient, compact, and robust backlight solutions in portable consumer electronics with stringent size and thermal constraints.

FAQ

What is the minimum recommended input capacitance for MP3309AGQ-P?

A 2.2μF to 10μF X5R/X7R ceramic capacitor is recommended, placed as close as possible to the VIN and GND pins. This reduces input ripple and high-frequency switching noise injection into the power source, ensuring stable operation under dynamic load conditions and preventing voltage droop during peak current demand.

Can MP3309AGQ-P drive more than one LED string simultaneously?

No - MP3309AGQ-P is a single-string WLED driver. It regulates current through one external sense resistor connected to FB and GND. Driving multiple strings requires either parallel configuration with matched LEDs (not recommended due to current imbalance) or separate MP3309AGQ-P units per string for independent, precise control.

How does the FREQ pin resistor value affect efficiency and EMI?

Lower fSW (e.g., 300kHz) improves light-load efficiency and reduces switching losses but increases inductor/transformer size and may worsen low-frequency EMI. Higher fSW (e.g., 1.2MHz) shrinks passive components and shifts EMI to less-sensitive bands but increases gate and switching losses. Optimal selection balances thermal performance, board area, and regulatory compliance.

What happens during an LED open-circuit fault?

When the LED string opens, FB voltage drops below 200mV, causing the error amplifier output to rise. The controller continues boosting until VOUT reaches the 35.5V OVP threshold, then halts switching. Once VOUT falls below 33.0V (35.5V – 2.5V hysteresis), normal operation resumes automatically - no manual reset required.

Is the BST capacitor mandatory, and what type is recommended?

Yes - the BST capacitor (typically 0.1μF X7R ceramic) between BST and SW is mandatory for gate-driving the internal synchronous MOSFET. Without it, the high-side switch cannot turn on, forcing non-synchronous operation with degraded efficiency and potential thermal issues. Placement must minimize loop inductance for reliable bootstrap charging.

Does MP3309AGQ-P support I²C or other digital interfaces?

No - MP3309AGQ-P uses only analog and PWM control signals (EN/PWML, PWMH, FREQ, FB). It lacks digital communication interfaces. Brightness and configuration are set externally via resistor networks and PWM timing; system-level digital control requires external microcontroller coordination.

What is the maximum continuous LED current supported?

The device does not specify a maximum LED current directly; instead, it limits peak inductor current to 1.4–1.8A (cycle-by-cycle) and supports typical LED currents up to ~100mA depending on external components. Practical max current is constrained by thermal limits (125°C TJ max), inductor saturation, and output capacitor ripple rating - design must verify thermal performance at target ILED.