Monolithic Power Systems Inc. MP4021GS-A-P

Overview

MP4021GS-A-P from Monolithic Power Systems is a primary-side control offline LED controller with integrated active PFC, implemented in SOIC8 package. It delivers ±1.5% load regulation, ≥0.9 power factor across universal AC input (85–265VAC), and real-current control without optocoupler or secondary feedback. Used in isolated single-stage flyback LED drivers for residential and commercial lighting.

For engineers reviewing the MP4021GS-A-P datasheet, MP4021GS-A-P pinout, MP4021GS-A-P application, or MP4021GS-A-P equivalent, key selection considerations include boundary conduction mode operation, 20µA start-up current, VCC UVLO thresholds (12.6V turn-on / 9.0V turn-off), and multi-protection architecture including OVP, OCP, OTP, and cycle-by-cycle current limiting.

Technical Context

The MP4021GS-A-P employs proprietary real-current control to regulate LED current using only primary-side signals-eliminating optocouplers and secondary feedback components. Its multiplier-based PFC architecture shapes the primary peak current waveform to match the rectified AC line voltage, achieving ≥0.9 PF over universal input.

It operates in boundary conduction mode (BCM) with internal minimum off-time (3.5µs) and leading-edge blanking (280ns on CS, 1.8µs on ZCD). Protection functions are tightly coupled: ZCD pin monitors both zero-current detection (0.31V threshold) and over-voltage (5.4V after 1.5µs blanking) and over-current (0.60V after 280ns blanking) conditions.

Key Specifications

Pinout & Package

MP4021GS-A-P is housed in an industry-standard SOIC8 package (5.0mm × 6.0mm, 1.27mm pitch), optimized for compact offline LED driver PCB layouts with thermal pad grounding and minimal creepage requirements.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side offline LED controller applications.

Compared with MP4021GS-A-P, MP4026GS-Z offers measurable improvements in start-up current, noise immunity, and longevity assurance-making it the recommended upgrade path-while MP4027GS-Z trades external component count for reduced design flexibility and thermal headroom.

Availability

MP4021GS-A-P is available at Aetrix Electronics and suitable for residential LED lamps, commercial downlights, industrial panel lighting, and outdoor streetlight drivers requiring stable component supply and legacy design continuity.

Supply support for MP4021GS-A-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 over 20 years of leadership in DC/DC converters, LED drivers, and motor drivers.

The MP4021 series belongs to MPS's primary-side LED controller product line, designed specifically to replace optocoupler-dependent secondary-side controllers in cost-sensitive, high-reliability offline lighting applications.

FAQ

What is the function of the MULT pin on MP4021GS-A-P?

The MULT pin receives a scaled-down half-wave sinusoidal signal from the rectified AC line via a resistor divider. This signal serves as the reference input to the internal multiplier, enabling active power factor correction by shaping the primary peak current waveform to match the input voltage waveform-achieving ≥0.9 PF across universal input range.

Can MP4021GS-A-P operate in constant-voltage (CV) mode?

Yes-MP4021GS-A-P supports primary-side constant-voltage regulation via the FB pin. When a resistor divider from the auxiliary winding is connected to FB, the internal 0.414V reference regulates the output voltage. This enables single-stage CV flyback designs for LED drivers requiring stable voltage rails, such as those feeding downstream DC-DC LED drivers like MP2489.

How does the ZCD pin provide both zero-current detection and over-voltage protection?

ZCD performs dual functions through time-gated sampling: during the MOSFET off interval, it detects the falling edge at 0.31V to trigger turn-on (zero-current detection); 1.5µs after turn-off, it samples voltage again-if >5.4V, OVP latches and shuts down the IC. Both functions share the same pin but are separated temporally and electrically via internal blanking timers and thresholds.

What is the purpose of the COMP pin, and what compensation network is recommended?

The COMP pin is the error amplifier output node for loop compensation. A series RC network (e.g., 10kΩ + 10nF) is typically connected between COMP and GND to stabilize the current regulation loop. For wide-output-voltage applications, a high-value resistor (>3MΩ) may inject VCC-derived voltage into COMP to compensate for LED forward-voltage variation.

Why is MP4021GS-A-P marked "Not Recommended for New Designs"?

MPS has superseded MP4021GS-A-P with MP4026GS-Z (enhanced performance, longer support) and MP4027GS-Z (integrated MOSFET). While MP4021GS-A-P remains functional and available, new designs should use MP4026GS-Z for guaranteed long-term supply, improved ESD robustness, and updated qualification data per JEDEC JESD47.

What is the maximum allowable continuous power dissipation for MP4021GS-A-P in SOIC8?

At TA = +25°C, the maximum continuous power dissipation is 1.3W, calculated from θJA = 96°C/W and TJ(MAX) = 150°C. Derating is required above +25°C ambient: PD(MAX) = (150°C − TA)/96°C/W. Exceeding this limit triggers internal thermal shutdown with auto-restart behavior upon VCC UVLO recovery.

How does the real-current control method achieve accurate LED current without secondary feedback?

Real-current control calculates LED current from primary-side parameters: ILED ≈ (VFB × NSEC) / (2 × RS), where VFB = 0.414V (internal reference), NSEC is secondary turns, and RS is the MOSFET source sense resistor. The IC uses ZCD timing and CS voltage to reconstruct secondary current waveform-enabling ±1.5% accuracy without optocoupler or secondary shunt.