Monolithic Power Systems Inc. MP3398AGS

Overview

MP3398AGS 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 between strings, supports 5V–28V input, and regulates LED current via external ISET resistor (VISET = 1.22V). Used in desktop monitors and 2D/3D TVs where precise multi-string current balance and dual-dimming flexibility are required.

For engineers reviewing the MP3398AGS datasheet, MP3398AGS pinout, MP3398AGS application, or MP3398AGS equivalent, key selection considerations include its SOIC16 package, peak-current-mode boost architecture with programmable switching frequency (150–621 kHz), integrated open/short LED protection, thermal shutdown recovery, and dual-dimming control via separate PWM and ADIM pins.

Technical Context

The MP3398AGS implements fixed-frequency peak-current-mode control with an external MOSFET gate driver (GATE pin) and internal 6V LDO (VCC) for biasing. Its regulation loop uses COMP pin compensation and senses inductor current via ISENSE to enforce cycle-by-cycle current limiting (145–230 mV threshold).

It integrates four independent current-sink channels (LED1–LED4) with <2.5% inter-string matching, driven by internal current sources referenced to 1.22V at ISET. Dimming is decoupled: PWM pin controls duty-cycle-based current chopping, while ADIM accepts DC (0.4–1.5V) or high-frequency PWM (>20 kHz) for linear amplitude scaling.

Key Specifications

Pinout & Package

MP3398AGS is packaged in SOIC16 with exposed pad (non-thermal, no internal connection). Pin functions are validated per MPS Rev. 1.06 datasheet and match TSSOP16-EP pinout mapping except for NC placements.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3398AGF and MP3398AGY, the MP3398AGS offers lowest profile and simplest assembly in SOIC16, making it optimal for cost-sensitive, medium-power backlight modules where thermal margin is sufficient and pin routing density is moderate.

Availability

MP3398AGS is available at Aetrix Electronics and suitable for desktop LCD monitors, flat panel video displays, and 2D/3D LCD TVs requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for MP3398AGS 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 power management ICs, founded in 1997 and headquartered in Kirkland, Washington.

The MP3398A belongs to MPS's WLED backlight controller product line, engineered specifically for large-format LCD panel illumination with emphasis on multi-string current precision, dual-dimming flexibility, and robust fault tolerance in consumer and commercial displays.

FAQ

What is the minimum recommended ISET resistor value for MP3398AGS?

The datasheet specifies a maximum LED current of 350 mA per string. With VISET = 1.22 V, the minimum RISET is calculated as 1.22 V / 0.35 A ≈ 3.49 kΩ. A standard 3.3 kΩ resistor yields ~370 mA, exceeding absolute max rating; therefore, 3.6 kΩ (330 mA) or 3.9 kΩ (313 mA) are safe, validated values per typical performance data.

Can MP3398AGS drive more than 4 LED strings?

Yes - MP3398AGS supports cascading: two or more ICs can share a single inductive power stage by connecting their GATE, VIN, and VCC nodes in parallel while keeping ISENSE tied to one master IC. Each IC independently regulates its 4 strings, enabling scalable 8+, 12+ string configurations without additional boost stages.

How does open-string protection operate on MP3398AGS?

When an LED string opens, its corresponding LEDX pin voltage drops below 196 mV. The IC detects this condition, marks the faulty string, and continues regulating remaining strings using the highest LEDX voltage as feedback reference. If all four strings open, the IC shuts down the boost converter entirely after OVP threshold violation.

Is the ADIM pin compatible with microcontroller GPIO outputs?

Yes - ADIM accepts DC voltages from 0.4 V to 1.5 V for linear dimming control. Most 3.3 V or 5 V MCU GPIOs can drive it directly via a resistive divider (e.g., 10 kΩ + 15 kΩ) to scale output to 0–1.5 V range. For PWM input, ensure frequency >20 kHz to leverage internal RC filtering and avoid unintended dimming ripple.

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

In standalone operation, ISENSE must be tied to GND per datasheet guidance. Leaving it floating risks erratic current limiting or startup failure. It is only actively used in cascaded configurations where one MP3398AGS senses inductor current for all paralleled controllers, eliminating redundant sense resistors and improving system accuracy.

Does MP3398AGS support spread-spectrum frequency modulation?

No - MP3398AGS uses fixed-frequency peak-current-mode control with oscillator frequency set solely by the external ROSC resistor. It does not implement dithering or spread-spectrum techniques; EMI reduction relies on careful PCB layout, input/output capacitor selection, and optional external snubbers per application note AN-107.

What is the maximum allowable voltage on the LEDX pins?

The absolute maximum rating for LED1–LED4 pins is +55 V, but functional overvoltage protection triggers at 6.3 V (short-string detection threshold). Sustained voltage above 6.3 V for 4096 switching cycles causes automatic disable of that string. Therefore, design must ensure worst-case LED string forward voltage plus margin stays below 6.3 V at all operating conditions.