Monolithic Power Systems Inc. MP3398AGF

Overview

MP3398AGF from Monolithic Power Systems is a 4-string white LED step-up controller with analog and PWM dimming, designed for large-size 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). It drives an external N-MOSFET and integrates OVP, OTP, UVP, LED open/short, and inductor/diode short protection.

For engineers reviewing the MP3398AGF datasheet, MP3398AGF pinout, MP3398AGF application, or MP3398AGF equivalent, key selection criteria include its TSSOP16-EP package with exposed thermal pad, dual dimming mode flexibility, programmable 150–621kHz switching frequency, and cascading capability for multi-IC LED channel expansion using a shared inductive power source.

Technical Context

The MP3398AGF implements peak-current-mode control with fixed-frequency PWM architecture, where switching frequency is set by an external resistor on the OSC pin (1.23V-regulated reference) and duty cycle is limited to 93%. Its internal 6V LDO (VCC) powers gate drive and logic, with UVLO hysteresis of 200mV and recoverable thermal shutdown at 150°C.

It employs four matched internal current sources for LED string regulation, achieving 2.5% inter-string current accuracy. Protection logic includes latched OVP triggered at 1.23V on the OVP pin, open-string detection via LEDX pin voltage monitoring (<196mV), and short-string detection at >6.3V on LEDX pins with 4096-cycle fault confirmation.

Key Specifications

Pinout & Package

The MP3398AGF is housed in a thermally enhanced TSSOP16-EP package with exposed pad connected to GND for improved heat dissipation (θJA = 45°C/W, θJC = 10°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3398AGS and MP3398AGY, the MP3398AGF offers superior thermal performance (2.78W continuous dissipation) and compact footprint-making it optimal for high-brightness, thermally constrained LCD backlight modules where reliability under sustained 350mA/string operation is essential.

Availability

MP3398AGF 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-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3398AGF 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, with design centers in the US, China, and Taiwan, and global distribution through authorized partners.

The MP3398A product line targets large-format LCD backlighting, delivering high-efficiency, multi-string LED control with integrated protection and flexible dimming-optimized for reliability in consumer and industrial display systems.

FAQ

What is the maximum allowable LED string voltage that MP3398AGF can regulate?

The MP3398AGF does not directly regulate string voltage; it regulates current per string while the boost output voltage self-adjusts to the highest forward voltage among active strings. The absolute maximum voltage at any LEDX pin is +55V, and the OVP threshold is programmable up to ~6.8V on the output bus via the OVP pin divider. Practical string voltage depends on LED count and V_F, but the IC supports typical 30–60V boost outputs with appropriate external MOSFET and diode selection.

Can MP3398AGF operate with only two LED strings connected?

Yes. The MP3398AGF automatically detects active strings via LEDX pin voltages and regulates only those with valid current paths. Unused LEDX pins (e.g., LED3 and LED4) must be left unconnected or tied to GND through ≥100kΩ resistors to avoid floating; the IC will ignore them and maintain regulation on the two active strings with full 2.5% matching accuracy.

How does the MP3398AGF handle mismatched LED forward voltages across strings?

The MP3398AGF uses a "lowest active LEDX voltage" feedback scheme: it senses all four LEDX pins and selects the smallest valid voltage to set the boost output bus level. This ensures sufficient headroom for the string with the highest V_F, while the internal current sources maintain precise 350mA regulation on each string regardless of individual V_F variation - eliminating cross-string current theft.

Is external compensation required on the COMP pin, and what capacitor value is recommended?

Yes, a ceramic capacitor (typically 1nF to 10nF, X7R or C0G) must be connected from COMP to GND to stabilize the current regulation loop. The exact value depends on selected inductor, output capacitance, and desired phase margin; MPS Application Note AN-107 recommends starting with 4.7nF and adjusting based on load transient response and output ripple measurements.

Does MP3398AGF support synchronization of switching frequency with an external clock?

No. The MP3398AGF uses an internal oscillator controlled solely by the external resistor on the OSC pin and does not provide an external sync input. Frequency is fixed per resistor value (e.g., 374kΩ → 180kHz); for synchronized multi-IC operation, designers must select identical ROSC values and rely on natural jitter suppression through shared input/output filtering.

What is the minimum PWM dimming frequency supported without visible flicker?

The MP3398AGF accepts PWM signals from 200Hz to 2kHz on the PWM pin. For flicker-free operation in static displays, ≥1kHz is recommended; for video content, ≥2kHz eliminates perceptible artifacts. At frequencies below 200Hz, LED current ripple increases and may cause audible coil whine or visible strobing - especially under camera capture.

How does the ISENSE pin function during cascaded operation with multiple MP3398AGF ICs?

In cascaded configurations, only one MP3398AGF (the master) uses ISENSE for peak-current-mode control; others configure ISENSE tied to GND to disable local current sensing. The master's ISENSE monitors total inductor current, while slave ICs synchronize switching and share the same boost rail - ensuring coordinated regulation without current-loop conflict.