Monolithic Power Systems Inc. HFC0300HS-LF-Z

Overview

HFC0300HS-LF-Z from Monolithic Power Systems is a variable off-time, current-mode flyback controller IC designed for universal-input AC/DC SMPS. It implements fixed-peak-current control with frequency foldback (65 kHz max → <20 kHz light load), peak-current compression to suppress transformer acoustic noise, active burst mode (VBURH = 3.2 V, VBURL = 3.1 V), and integrated high-voltage startup (700 V HV pin). It targets compact, high-efficiency offline adapters and battery chargers.

For engineers reviewing the HFC0300HS-LF-Z datasheet, HFC0300HS-LF-Z pinout, HFC0300HS-LF-Z application, or HFC0300HS-LF-Z equivalent, key selection criteria include its SOIC-7 package, 8.2–20 V VCC operating range, 0.5 V current-sense threshold, thermal shutdown with 25°C hysteresis, and OVP latch-off at 24 V with 3.0 V reset.

Technical Context

The HFC0300HS-LF-Z uses a voltage-controlled oscillator architecture where the FSET pin capacitor (charged by 28 µA current source) sets maximum switching frequency, while COMP pin feedback dynamically adjusts off-time to regulate output. Its fixed-peak-current loop enables boundary conduction mode (BCM) operation across universal input (85–265 VAC) without external slope compensation in most designs.

Protection logic integrates digital timing: overload protection triggers after 74 ms delay (CFSET = 330 pF), short-circuit protection activates at CS ≥ 1.0 V with 200 ns leading-edge blanking, and over-voltage protection employs a 20 µs time-constant filter on VCC to enforce latched shutdown above 24 V until VCC drops to 3.0 V.

Key Specifications

Pinout & Package

Package: SOIC-7 (7-pin small outline integrated circuit), RoHS-compliant, surface-mount, thermal resistance θJA = 96°C/W (4-layer PCB).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar flyback controller applications.

Compared with UCC28740 and ICE2QS03G, the HFC0300HS-LF-Z delivers superior light-load efficiency through monolithic burst mode and frequency foldback, eliminates external HV start-up components, and integrates all protections in a single SOIC-7 package - reducing total solution size by ≥30% and bill-of-materials cost by $0.18–$0.25 per unit.

Availability

HFC0300HS-LF-Z is available at Aetrix Electronics and suitable for USB-C wall adapters, smart home IoT power supplies, industrial sensor transmitters, and medical auxiliary modules requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for HFC0300HS-LF-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 analog and power ICs, with design centers in the US, China, and Taiwan, and global distribution.

The HFC0300 belongs to MPS's offline AC/DC controller product line, engineered specifically for high-efficiency, low-noise, and ultra-low-standby-power flyback converters targeting consumer, industrial, and medical power applications.

FAQ

What is the minimum FSET capacitor value required for stable operation?

The FSET capacitor must be sized to ensure the voltage across it remains within 0.82–3.2 V during operation. For 65 kHz maximum frequency, Equation (9) specifies CFSET ≈ 430 pF (using 28 µA charge current and 0.88 V threshold). A 330 pF capacitor yields ~74 kHz, exceeding datasheet max; 470 pF is recommended for margin and temperature stability.

How does the HFC0300HS-LF-Z prevent transformer acoustic noise at light loads?

It combines two mechanisms: frequency foldback reduces switching frequency below audible range (<20 kHz), and peak-current compression actively lowers the 0.5 V current-sense threshold proportionally as load decreases - both suppressing mechanical resonance excitation in ferrite cores and windings.

Can the HFC0300HS-LF-Z operate without an auxiliary winding?

No. While the HV pin provides high-voltage startup current, the IC requires sustained VCC bias from an auxiliary winding once startup completes. If the auxiliary winding fails or is omitted, VCC drops below 8.2 V and the controller shuts down, then re-engages HV current source - causing unstable oscillation or no regulation.

What is the purpose of the 0.6 µs delay after FSET capacitor discharge?

This fixed delay ensures consistent minimum off-time and prevents premature re-triggering of the oscillator. It guarantees the FSET capacitor fully discharges to near 0 V before the next charging cycle begins - stabilizing frequency control and preventing sub-harmonic oscillation under dynamic load conditions.

Does the HFC0300HS-LF-Z require external slope compensation in CCM operation?

Only when duty cycle exceeds 50% in continuous conduction mode. The datasheet recommends ramp compensation (e.g., 33 pF + 510 kΩ from DRV to CS) for CCM designs above 40 W. At ≤40 W and BCM operation - typical for this controller - slope compensation is unnecessary due to inherent stability of fixed-peak-current control.

How is over-voltage protection (OVP) reset after latching?

OVP causes hard latch-off: the controller stops switching and holds VCC > 24 V until mains power is cycled. Reset occurs only when VCC falls below 3.0 V - typically achieved by unplugging the AC input and reapplying power. No software or signal-based reset is supported; this ensures safety-critical isolation integrity.

What is the thermal shutdown hysteresis and why is it critical?

Thermal shutdown trips at 150°C and releases at 125°C - a 25°C hysteresis prevents rapid on/off cycling near the limit. This protects the IC and external MOSFET during sustained overload or poor heatsinking, allowing safe cooldown before resuming operation without external intervention.