Monolithic Power Systems Inc. MP4658GS-Z

Overview

MP4658GS-Z from Monolithic Power Systems is a 4-string, secondary-side LED driver IC for LCD backlighting systems, regulating LED current up to 200mA per string with 80V cathode return capability and ±1.5% current matching. It controls flyback power stages via optocoupler feedback (OPT pin), supports analog dimming (>5kHz ADIM input) and PWM dimming (100Hz–1kHz PDIM input), and delivers <2% LED current accuracy. It is designed for monitor and small-TV backlight applications requiring precise multi-string current balance and AC/DC feedback loop coordination.

For engineers reviewing the MP4658GS-Z datasheet, MP4658GS-Z pinout, MP4658GS-Z application, or MP4658GS-Z equivalent, key selection criteria include its dual-compensation architecture (COMP1 for LED current loop, COMP2 for output voltage loop), SOIC-16 package thermal performance (θJA = 80°C/W), integrated open/short LED protection, and compatibility with 6V–36V input supply rails in secondary-side-controlled flyback topologies.

Technical Context

The MP4658GS-Z implements a dual-loop control architecture: COMP1 regulates the minimum VLEDx across four strings during PWM-on periods using a transconductance amplifier (GM_COMP1 = 720 μA/V), while COMP2 manages system output voltage (VOUT) regulation during PWM-off periods (GM_COMP2 = 260 μA/V). Both loops drive an external optocoupler-connected flyback controller via the OPT pin.

It integrates fault detection logic that monitors OVP (2.4V threshold on OVP pin), FB open condition (<500mV), LEDx short-to-ground (via COMP1 saturation + low VLEDx for 30ms), and thermal shutdown at 150°C with 25°C hysteresis. Dimming is decoupled: ADIM accepts >5kHz signals for analog or soft-PWM modulation, while PDIM accepts low-frequency PWM (≥100Hz) for direct brightness control.

Key Specifications

Pinout & Package

MP4658GS-Z is housed in a standard SOIC-16 package (5.3mm × 10mm, 1.27mm pitch), optimized for thermal dissipation (θJA = 80°C/W) and surface-mount assembly in compact backlight driver PCBs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-string LED driver applications.

Compared with MPQ4658-AEC1, the MP4658GS-Z offers identical functionality at lower cost and qualification overhead for industrial/commercial displays; versus LM3409QMY/NOPB, it reduces component count by integrating 4-channel balancing, dual dimming inputs, and fault management - cutting PCB area by ~35% and eliminating 8 external op-amps and references.

Availability

MP4658GS-Z is available at Aetrix Electronics and suitable for LCD monitor backlighting, small-TV LED drivers, and commercial flat-panel displays requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP4658GS-Z 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 MP4658 belongs to MPS's LED backlight driver product line, engineered specifically for secondary-side-controlled flyback architectures in cost-sensitive, space-constrained display applications where precision current matching and integrated fault resilience are critical.

FAQ

What is the maximum LED string voltage the MP4658GS-Z can support?

The MP4658GS-Z supports up to 80V cathode return per string, verified by absolute maximum rating (LEDx = −0.3V to +80V) and OVP protection threshold (2.4V on OVP pin with external divider). This enables driving strings of up to 20 white LEDs (3.8V typical Vf) or 12 high-Vf red/amber LEDs (6.2V typical) without external voltage clamping.

How does the MP4658GS-Z handle a single open LED string?

When one LED string opens, the MP4658GS-Z detects VLEDx falling below 100mV while VOVP rises to 2.4V, then marks off that string and continues regulating the remaining three. The system enters partial-operation mode with automatic recovery once the fault clears - confirmed in Figure 9 (One String Open waveform) and Section "Open LED Protection".

Can the MP4658GS-Z operate without an optocoupler?

No - the OPT pin is designed exclusively for driving an external optocoupler to close the feedback loop with the primary-side flyback controller. There is no internal error amplifier output or direct PWM interface; removing the optocoupler breaks regulation and causes uncontrolled VOUT/ILED behavior per functional block diagram and "Operation" section.

What is the minimum recommended ISET resistor value for 200mA per string?

Using ILED = (80kΩ × 200mA) / R_ISET(kΩ) from Equation (3), a 320kΩ resistor yields 50mA; for 200mA, R_ISET = 80kΩ × 200mA / 200mA = 80kΩ. Minimum validated value is 32kΩ (per Table "LED Current Regulation", RISET = 320kΩ → 50mA), so 80kΩ is within spec and achieves target current with ±1.5% matching.

Does the MP4658GS-Z support I²C or digital dimming interfaces?

No - the MP4658GS-Z provides only analog (ADIM) and PWM (PDIM) dimming inputs. It lacks any serial interface, register map, or digital control logic. Dimming resolution and update rate depend solely on external signal generator fidelity and ADIM/PDIM pin AC characteristics (e.g., 5kHz min ADIM frequency, 100Hz min PDIM frequency).

How is thermal protection implemented and reset?

Thermal protection triggers at 150°C junction temperature, halting switching and pulling FF low. Recovery occurs automatically when die temperature falls to 125°C (25°C hysteresis), restoring normal operation without external intervention - confirmed in "Thermal Protection" section and Absolute Maximum Ratings table.

What is the purpose of the NC pin (Pin 14) and can it be grounded?

Pin 14 is Not Connected - it has no internal bond wire or circuit connection. Grounding it introduces risk of PCB contamination-induced leakage or ESD path disruption. Datasheet explicitly states "must remain unconnected", and Figure 4 PCB layout shows it floating. Violating this may cause unpredictable startup or fault behavior.