Monolithic Power Systems Inc. MP3398LGS-P

Overview

MP3398LGS-P from Monolithic Power Systems is a 4-string white LED boost 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 150–621kHz frequency - used in desktop monitors and 3D TVs.

For engineers reviewing the MP3398LGS-P datasheet, MP3398LGS-P pinout, MP3398LGS-P application, or MP3398LGS-P equivalent, key selection criteria include its dual-dimming capability, cascading support for multi-IC LED arrays, OVP/OTP/LED open-short protection, and SOIC16 package compatibility with thermal design constraints.

Technical Context

The MP3398LGS-P implements peak-current-mode control with fixed-frequency oscillator (programmable via ROSC resistor) and internal 6V LDO (VCC) powering gate driver and logic. Its four independent current sinks regulate LED strings using ISET-resistor-set reference (1.225V), achieving 2.5% inter-string matching via matched internal current sources.

It integrates dual-dimming paths: PWM input (pin 3) directly chops LED current, while ADIM (pin 7) accepts DC (0.4–1.5V) or filtered PWM (>20kHz) to linearly scale current amplitude. Protection includes recoverable thermal shutdown (150°C trigger, 25°C hysteresis), latch-off OVP (1.225V threshold), and LED short detection (6.3V on LEDx pins).

Key Specifications

Pinout & Package

MP3398LGS-P is housed in a 16-pin SOIC package with exposed pad (thermal enhancement), rated for 150°C junction temperature and 80°C/W θJA on 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3394SGS-P and LM3409QMY/NOPB, the MP3398LGS-P uniquely supports 4-string operation with ±2.5% matching, dual analog/PWM dimming, and cascading - making it the only fit for large-panel backlighting requiring uniformity, flexibility, and scalability.

Availability

MP3398LGS-P 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 assurance, and RoHS-compliant manufacturing.

Supply support for MP3398LGS-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 focus on efficiency, integration, and reliability for power management applications.

The MP3398LGS-P belongs to MPS's WLED backlight controller product line, engineered specifically for large-format LCD panel illumination with emphasis on current matching, thermal resilience, and flexible dimming architecture.

FAQ

What is the maximum total output power supported by MP3398LGS-P?

The MP3398LGS-P does not specify a fixed wattage limit but supports up to 350mA per string across 4 strings with V_OUT up to ~55V (based on 28V input and typical boost ratio). At 350mA × 4 strings × 30V typical V_LED, output power reaches ~42W. Actual limit depends on thermal design, MOSFET selection, and PCB copper area - SOIC16 θ_JA = 80°C/W constrains continuous dissipation to ~1.56W at 25°C ambient.

Can MP3398LGS-P drive LEDs with forward voltage exceeding 30V per string?

Yes - the boost converter output is limited only by external components and OVP setting. The IC regulates based on the highest LED string voltage, and V_LEDX pins tolerate up to 55V. With proper OVP resistor divider (e.g., 1.2× nominal V_OUT) and MOSFET V_DS rating ≥1.5× expected V_OUT, strings with 35–45V V_F are supported, provided inductor saturation current and diode PIV ratings are sufficient.

How does the MP3398LGS-P handle an open LED string during operation?

When an LED string opens, its corresponding LEDx pin voltage drops below 196mV. The IC detects this, marks that string as faulty, and continues regulating remaining strings using the highest active LEDx voltage as feedback reference. If all strings open, the IC shuts down the boost converter after OVP threshold is reached - preventing uncontrolled voltage rise.

Is the ADIM pin compatible with standard microcontroller DAC outputs?

Yes - the ADIM pin accepts DC voltages from 0.4V to 1.5V for linear LED current control. A typical 12-bit MCU DAC (0–3.3V) can interface directly using a resistive divider (e.g., 10kΩ + 15kΩ) to scale 0–3.3V to 0–1.5V. Input bias current is negligible (<100nA), so no buffer is required for standard DACs.

What is the minimum recommended PWM dimming frequency for flicker-free operation?

For perceptually flicker-free dimming, use ≥1kHz PWM on the PWM pin. The datasheet confirms stable operation down to 100Hz, but human eye sensitivity peaks near 10–20Hz; frequencies ≥1kHz eliminate visible modulation. At 2kHz, minimum duty cycle is 3%, enabling dimming to <1% brightness without strobing artifacts.

Does MP3398LGS-P support synchronization of switching frequency across multiple ICs?

No - the MP3398LGS-P uses an internal oscillator set by ROSC resistor and lacks SYNC or CLKIN pins. Cascaded units operate asynchronously, which reduces beat-frequency EMI but prevents phase-aligned switching. For synchronized operation, external clock injection is not supported; alternative controllers like MPQ3367 would be required.

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

In standalone (non-cascaded) operation, ISENSE must be tied to GND. It is not used for current sensing - that function is handled internally via the external R_SENSE between MOSFET source and GND. Leaving ISENSE floating risks erratic behavior; grounding it disables cascading mode and ensures normal peak-current-mode control.