Monolithic Power Systems Inc. MP4078GS-Z

Overview

MP4078GS-Z from Monolithic Power Systems is a primary-side regulation (PSR) offline controller with integrated active PFC for constant-voltage LED drivers and front-end pre-regulators. It operates in discontinuous conduction mode (DCM) with valley switching, delivers <50 mW no-load power at 230 VAC, achieves >0.9 PF across universal input (90–265 VAC), and integrates a 35 V/320 mΩ internal low-side MOSFET in SOIC-8. Used in smart LED lighting systems requiring optocoupler-free isolation and high efficiency.

For engineers reviewing the MP4078GS-Z datasheet, MP4078GS-Z pinout, MP4078GS-Z application, or MP4078GS-Z equivalent, this page provides verified technical context, SOIC-8 pin mapping with circuit roles, PSR + PFC control architecture details, real-world performance metrics (PF, THD, transient response), and validated alternative controllers for CV offline designs.

Technical Context

The MP4078 implements constant-on-time (COT) control with input voltage sensing via the MULT pin to maintain high power factor across 90–265 VAC input. Its on-time generator uses a slew-rate capacitor charged by VMULT-derived current and compared against COMP voltage - with VCOMP_HALF (2.2 V) enabling fixed on-time under light load to sustain regulation.

Primary-side regulation relies on zero-current detection (ZCD pin) with adaptive blanking delay (1.16–1.79 µs based on S-pin current), sample-and-hold feedback reconstruction, and valley-switching logic triggered by ZCD falling edges with 300 ns turn-on delay. Protection includes OVP (2.96 V FB threshold), SCP (200 mV FB threshold, 6 ms duration), and OTP (160 °C).

Key Specifications

Pinout & Package

MP4078GS-Z is housed in an SOIC-8 package with exposed pad (thermal pad not electrically connected). Pin 1 is GATE; pin 5 is GND; pin 8 is D (drain of internal MOSFET). All pins are rated for -0.3 V to +28 V except ZCD (-0.7 V to +6.5 V) and D (-0.7 V to +35 V).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PSR + PFC offline controller applications.

Compared with MP4077GS-Z, MP4078GS-Z delivers higher integration (integrated 35 V MOSFET) and simpler layout but less voltage headroom; versus UCC28056DR, it offers lower component count and better light-load efficiency but trades off CV precision and maximum power capability.

Availability

MP4078GS-Z is available at Aetrix Electronics and suitable for smart LED lighting, front-end pre-regulators, high-efficiency AC-DC adapters, and IoT gateway power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for MP4078GS-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 over 20 years of expertise in DC-DC, AC-DC, motor drivers, and LED controllers.

The MP4078 belongs to MPS's PSR+PFC offline controller product line, designed specifically for cost-sensitive, space-constrained constant-voltage LED and industrial pre-regulator applications demanding high PF, low THD, and ultra-low standby power.

FAQ

What is the minimum recommended ZCD resistor divider ratio for a 50 V output?

For a 50 V output with typical diode drop (0.7 V), NAUX:NS = 12:12, and RZCD2 = 10 kΩ, Equation (1) yields RZCD1 ≈ 22.1 kΩ. The datasheet confirms RZCD1//RZCD2 = 2.8–3.3 kΩ or >8.8 kΩ for tCYCLE_MIN configuration - so 22.1 kΩ/10 kΩ satisfies the high-ratio option and ensures stable ZCD sampling under all loads.

Does MP4078GS-Z support non-isolated buck-boost topologies?

Yes - the datasheet explicitly states MP4078 supports non-isolated topologies including buck-boost. Its PSR architecture adapts to auxiliary winding sensing in isolated designs or direct output sensing in non-isolated configurations, and the integrated MOSFET's 35 V rating suits typical 12–24 V buck-boost outputs.

How does the MULT pin enable brownout protection?

The MULT pin senses rectified input via RMULT_UP/RMULT divider. When VMULT falls below 210 mV (typical brownout threshold), the IC disables switching and enters latch-off state until VMULT rises above 320 mV (brown-in threshold), providing 110 mV hysteresis to prevent chatter during marginal line conditions.

What is the purpose of the cascode MOSFET architecture?

The cascode architecture uses the internal low-side MOSFET (D/S pins) to drive an external high-voltage MOSFET's source. This enables fast VCC charging from the D pin during start-up - eliminating the need for a high-voltage startup resistor and reducing start-up time to 49 µs while maintaining safe gate drive levels.

Can MP4078GS-Z achieve constant current (CC) output for LED strings?

No - MP4078 is specified exclusively for constant voltage (CV) output applications. Its feedback loop regulates VFB against 2.49 V reference, and protections (OVP, SCP) are calibrated for voltage-based fault detection. For CC LED drivers, MPS recommends MPQ4077 or MP4088 families.

What thermal derating applies above 25°C ambient?

With θJA = 96 °C/W, maximum continuous power dissipation drops linearly: PD(MAX) = (150°C − TA)/96. At 70°C ambient, PD(MAX) = 0.83 W - requiring careful PCB copper area allocation around the SOIC-8 thermal pad and monitoring of internal MOSFET temperature rise during full-load operation.