Monolithic Power Systems Inc. MP4657BGS-P

Overview

MP4657BGS-P from Monolithic Power Systems is a single-stage flyback LED driver and system voltage controller for secondary-side LCD backlighting, integrating 4-string LED current balancing, ±1.5% LED current accuracy, ±1.5% system voltage accuracy, and independent regulation of ILED and VSYS using dual compensation loops (ICOMP/DCOMP). It operates from 4V–16V input and supports analog/PWM dimming via ADIMP/PWM pin.

For engineers reviewing the MP4657BGS-P datasheet, MP4657BGS-P pinout, MP4657BGS-P application, or MP4657BGS-P equivalent, key selection considerations include its SOIC-16 package, 80V LED string capability, soft-switching N-MOSFET gate drive, optocoupler-based primary-side control interface, and integrated protections including LED open/short, VSYS OVP, and thermal shutdown.

Technical Context

The MP4657BGS-P implements dual-loop regulation: the ICOMP loop controls flyback power stage for precise 4-string LED current (ILED) regulation with min-VLEDx sensing and 2% current matching; the DCOMP loop dynamically switches between duty-cycle control of an external N-channel MOSFET (PWM active) and direct flyback control (PWM inactive) to regulate VSYS.

Its SYNC pin synchronizes GATE turn-off to primary-side flyback switching edges to enable zero-current turn-on of the external MOSFET, reducing voltage spikes and switching loss. Protection logic includes latched OVP at 3V on OVP pin, feedback open-loop detection after 1024 cycles, and separate fault thresholds for LED overvoltage (2.4V), slow OV (4.9V), and fast OV (20V).

Key Specifications

Pinout & Package

MP4657BGS-P is housed in a standard SOIC-16 package with exposed pad (not thermally enhanced), rated MSL Level 2, and designed for surface-mount assembly on 4-layer PCBs with θJA = 80°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar single-stage flyback LED driver and system voltage controller applications.

Compared with MP4657BGS-P, MP4655AGS-Z sacrifices 20V LED headroom and synchronization capability for lower unit cost, while LM3445MMX/NOPB shifts regulation intelligence to the primary side, requiring additional discrete components to match MP4657BGS-P's integrated secondary-side functionality and protection set.

Availability

MP4657BGS-P is available at Aetrix Electronics and suitable for LCD TV backlight systems, desktop monitor power supplies, industrial flat-panel displays, and medical imaging displays requiring stable component supply, full production traceability, and long-term lifecycle support.

Supply support for MP4657BGS-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 power management ICs, with over two decades of expertise in DC-DC conversion, LED drivers, and motor control solutions.

The MP4657BGS-P belongs to MPS's secondary-side LED backlight controller product line, engineered specifically for high-efficiency, compact, and fault-resilient LCD display power architectures requiring integrated LED current balancing and system voltage regulation.

FAQ

What dimming methods does MP4657BGS-P support, and how are they distinguished?

The MP4657BGS-P supports both analog and PWM dimming via the ADIMP/PWM pin. Analog dimming requires a pulse signal above 5kHz, which continuously adjusts LED current proportionally to duty cycle. PWM dimming uses signals below 5kHz to fully switch LED current on/off, enabling high-contrast dimming without color shift. The IC automatically detects mode based on input frequency.

How does MP4657BGS-P achieve soft switching of the external N-MOSFET?

Soft switching is achieved by synchronizing the GATE turn-off edge to the falling edge of the SYNC signal, which is derived from the secondary-side flyback winding. This ensures the N-MOSFET turns off precisely when secondary current reaches zero, enabling zero-current turn-on and minimizing voltage spikes and switching losses during subsequent conduction.

What protections are implemented for the LED driver stage?

The LED driver stage includes LED open protection (OVP pin >2.4V), LED short protection (slow OV at 4.9V, fast OV at 20V), LEDx pin short-to-ground detection, and thermal shutdown at 150°C. All protections trigger fault indication on the ISET/FAULT pin and can latch off the IC depending on severity and configuration.

Can MP4657BGS-P regulate both LED current and system voltage simultaneously?

Yes - when the PWM signal is active, MP4657BGS-P regulates LED current via the ICOMP loop controlling the flyback power stage, while simultaneously regulating system voltage (VSYS) via the DCOMP loop controlling the duty cycle of the external N-MOSFET. This dual-loop architecture ensures independent, high-accuracy control of both outputs.

What is the function of the SYNC pin, and what external connection is required?

The SYNC pin receives a synchronized signal from the secondary-side winding of the flyback transformer via a resistive divider. Its falling edge triggers GATE turn-off, aligning the N-MOSFET switching with primary-side operation. This connection is mandatory for soft switching and must be AC-coupled with appropriate voltage scaling to stay within -0.3V to +6V absolute maximum ratings.

How is LED current set, and what tolerance does it provide?

LED current is set by connecting a resistor from the ISET/FAULT pin to ground. With RISET = 320kΩ, nominal ILED is 50mA ±1.5%. At 40% dimming (20mA), accuracy remains ±3%, and current matching across four strings is 0.3–2% at 50mA and 0.6–2.5% at 20mA, verified over temperature.

Does MP4657BGS-P require an external optocoupler, and why?

Yes - the OPT pin drives the LED side of an external optocoupler to close the primary-side flyback regulation loop. This galvanic isolation enables accurate VSYS and ILED regulation on the secondary side while maintaining safety compliance and noise immunity in AC/DC offline converters.