Monolithic Power Systems Inc. MP020A-5GS

Overview

MP020A-5GS from Monolithic Power Systems is an offline primary-side flyback controller IC with integrated 700V MOSFET, delivering precise constant-current (CC) and constant-voltage (CV) regulation for low-power AC/DC adapters without optocoupler or secondary feedback. It supports 5W adapter output (85–265VAC), features 10Ω R_DS(ON), 30mW no-load consumption, and operates in DCM using variable off-time control.

For engineers reviewing the MP020A-5GS datasheet, MP020A-5GS pinout, MP020A-5GS application, or MP020A-5GS equivalent, key selection considerations include its SOIC8-7A package, 4V FB threshold, 380mA current limit, 120Hz minimum switching frequency, and integrated OVP/OCP/OTP/OCkP protection for cost-sensitive, EMI-constrained battery charger designs.

Technical Context

The MP020A-5GS implements primary-side regulation via auxiliary winding voltage sampling at FB, with 3.5µs delayed OVP detection and 120mV DCM threshold to enforce discontinuous conduction mode across load and line conditions. Its internal 700V MOSFET enables direct high-voltage start-up through the DRAIN pin, eliminating external HV bias circuitry.

Constant-current regulation relies on ZCD-based duty-cycle estimation and a fixed 0.152A I_{O_REF}, while CV mode uses FB voltage sampling referenced to 4.0V ±3%. Cable compensation is implemented via CP pin, generating up to 2V DC voltage proportional to load current for dynamic output voltage adjustment.

Key Specifications

Pinout & Package

MP020A-5GS is housed in a SOIC8-7A package (JEDEC MS-012 compliant), featuring gull-wing leads, 1.27mm pitch, and exposed thermal pad design optimized for PCB heat dissipation in compact adapters.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side CC/CV flyback controller applications.

Compared with MP020A-5GS, MP023DN supports higher power but sacrifices cable compensation, while INN2214K improves CV accuracy and safety features at the cost of added component count and design complexity.

Availability

MP020A-5GS is available at Aetrix Electronics and suitable for cell phone chargers, USB wall adapters, and standby power supplies requiring stable component supply, RoHS-compliant packaging, and long-term lifecycle support.

Supply support for MP020A-5GS 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 core expertise in DC/DC conversion, LED drivers, and AC/DC controllers.

The MP020A-5GS belongs to MPS's offline primary-side regulator product line, designed specifically for cost-sensitive, low-power (<10W) AC/DC adapters where simplicity, EMI performance, and no-load efficiency are critical.

FAQ

What is the purpose of the CP pin on MP020A-5GS?

The CP pin outputs a DC voltage (0–2V) proportional to load current, used to inject compensating current into the FB resistor divider. This dynamically raises the regulated output voltage under load to offset cable voltage drop, ensuring ±5% regulation at the device connector rather than at the transformer secondary.

How does MP020A-5GS achieve primary-side constant-current regulation without secondary sensing?

It uses zero-current detection (ZCD) on the auxiliary winding to estimate secondary diode conduction time, then calculates output current via the relationship I_O ∝ V_ZCD × I_PK. The internal IO_REF is fixed at 0.152A, and the error signal adjusts MOSFET on-time to maintain this value across line and load variations.

Can MP020A-5GS operate without an auxiliary winding?

No. The auxiliary winding is mandatory: it provides both VCC bias after start-up and the sampled voltage for FB-based CV/CC regulation. Without it, the IC cannot sustain operation beyond initial HV start-up, and regulation loops fail entirely.

What is the significance of the 3.5µs delay in FB OVP detection?

This delay ensures OVP sampling occurs after switching noise and ringing on the FB node have settled, preventing false trips during normal DCM transitions. It aligns with the chip's internal timing window for valid voltage measurement, making OVP robust against transient disturbances.

Does MP020A-5GS require a dummy load for stable no-load operation?

Yes. Due to its minimum 120Hz switching frequency, output voltage can rise above regulation without load. A ~10mW dummy load (e.g., 2.2MΩ across 5V) ensures stable CV mode entry and prevents OVP triggering during no-load standby.

How is thermal performance managed in the SOIC8-7A package?

The package relies on PCB copper area connected to pins 2/5/6 (GND) as the primary heat conduction path. Designers must provide ≥1 in² of top-side copper tied to GND, with multiple vias to inner-layer ground planes, to maintain junction temperature ≤125°C at full 5W load.

What protection features activate during open-circuit fault conditions?

Open-circuit protection (OCkP) triggers when the FB pin fails to detect a ≥120mV falling edge per cycle-indicating loss of secondary conduction. The IC shuts down drive pulses and enters hiccup mode, resuming only after the fault clears and VCC recycles through UVLO.