Monolithic Power Systems Inc. MP3398LGS

Overview

MP3398LGS from Monolithic Power Systems is a 4-string white LED step-up controller with analog and PWM dimming, designed for large LCD panel backlighting. It delivers up to 350mA per string, achieves ±2.5% current matching across strings, supports 4.5V–28V input, and regulates output via external MOSFET switching at programmable frequencies (150–621 kHz). Used in desktop monitors and 3D TVs where precise multi-string current control and dual-dimming flexibility are required.

For engineers reviewing the MP3398LGS datasheet, MP3398LGS pinout, MP3398LGS application, or MP3398LGS equivalent, this page provides verified technical context, SOIC16 package mapping, real-world dimming implementation guidance, thermal shutdown behavior, and validated alternative WLED controllers for backlight systems requiring cascaded boost architecture and open/short string protection.

Technical Context

The MP3398LGS implements peak-current-mode control with fixed-frequency PWM using an external resistor on the OSC pin to set switching frequency between 150 kHz and 621 kHz. Its internal 6V LDO (VCC) powers gate drive and logic, with UVLO activation at 3.4V (rising) and 280mV hysteresis.

It integrates four matched current sinks (LED1–LED4) referenced to a 1.225V ISET voltage, enabling 2.5% inter-string current regulation. Protection includes recoverable thermal shutdown (150°C trip, 25°C hysteresis), OVP (1.225V threshold on OVP pin), and cycle-by-cycle current limiting (640mV ISENSE threshold).

Key Specifications

Pinout & Package

MP3398LGS is housed in a 16-pin SOIC package with exposed pad (standard JEDEC MS-012AC), optimized for thermal dissipation in high-current LED driver applications. Pin 1 is marked by a dot; pin numbering follows standard SOIC top-view convention.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ3326-AEC1, MP3398LGS offers cascading and programmable frequency but lacks AEC-Q100 certification; versus RT9397BF, it delivers 2.3× higher per-string current, 33% more strings, and full external power stage control - essential for large-panel efficiency and thermal management.

Availability

MP3398LGS is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, 2D/3D LCD TVs, and industrial control panels requiring stable component supply, long-lifecycle availability, and consistent parametric performance across production batches.

Supply support for MP3398LGS 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 distribution through authorized partners.

The MP3398LGS belongs to MPS's WLED backlight controller product line, engineered specifically for large-format LCD backlighting systems demanding high current accuracy, dual dimming flexibility, and robust fault handling in commercial and industrial environments.

FAQ

What is the minimum recommended PWM dimming frequency for the MP3398LGS?

The MP3398LGS supports PWM dimming from 200 Hz to 2 kHz on the dedicated PWM pin. Below 200 Hz, visible flicker may occur; above 2 kHz, gate drive losses increase without perceptible benefit. For video applications, 1–2 kHz is optimal to balance flicker suppression and efficiency.

Can the MP3398LGS drive LED strings with different forward voltages?

Yes. The MP3398LGS automatically selects the highest active LEDX pin voltage to regulate the boost output, ensuring sufficient headroom for all strings. This allows mixed-V_f strings (e.g., 2.8V and 3.4V LEDs) to operate simultaneously with matched current.

How does the MP3398LGS handle an open LED string fault?

When an LED string opens, its corresponding LEDX pin is pulled low. The IC detects this condition, marks the faulty string, and continues regulating remaining strings using the highest unmarked LEDX voltage. If all strings open, the IC shuts down the boost converter.

Is external compensation required for stable operation?

Yes. A Type II compensation network (resistor + capacitor + optional capacitor) must be connected between COMP and GND to stabilize the current regulation loop. Typical values are 100kΩ in series with 1nF, plus a 10pF capacitor across the resistor, per MPS AN-107 design guidelines.

What is the purpose of the ISENSE pin in non-cascaded applications?

In standalone operation, the ISENSE pin must be tied directly to GND. Leaving it floating risks erratic current limiting or startup failure. It is only used in cascaded configurations to synchronize multiple MP3398LGS ICs sharing one inductor and diode.

Does the MP3398LGS support analog dimming with a DC voltage input?

Yes. Applying a DC voltage from 0.4V to 1.5V to the ADIM pin linearly scales LED current from 0% to 100%. Voltages below 0.4V or above 1.5V saturate the dimming range and may cause instability; internal clamping limits exceedance.

What thermal derating applies to the SOIC16 package at 85°C ambient?

With θ_JA = 80°C/W, maximum power dissipation at T_A = 85°C is (150°C − 85°C)/80°C/W = 0.81W. At full 350mA × 4 strings and 28V input, thermal design must include copper pour, vias, and airflow to avoid exceeding this limit.