Monolithic Power Systems Inc. HFC0500GS

Overview

HFC0500GS from Monolithic Power Systems is a fixed-frequency current-mode flyback controller with internal slope compensation, designed for medium-power offline AC/DC power supplies. It delivers 65 kHz nominal switching frequency, supports frequency foldback down to 25 kHz, enters burst mode below 0.7 V FB, and achieves ≤79 mW no-load power at 265 VAC - meeting EuP Lot 6 requirements. It integrates HV startup, X-cap discharge, and programmable OLP for notebook adapters and LCD TV power stages.

For engineers reviewing the HFC0500GS datasheet, HFC0500GS pinout, HFC0500GS application, or HFC0500GS equivalent, key selection criteria include its 700 V HV pin rating, 25 kHz minimum foldback frequency, burst-mode entry/exit thresholds (0.7 V / 0.8 V FB), integrated X-cap discharge timing, and SOIC8-7A package compatibility with standard flyback transformer designs.

Technical Context

HFC0500GS implements fixed-frequency current-mode control with 25 mV/μs internal slope compensation to prevent subharmonic oscillation in CCM operation above 50% duty cycle. Its dual-stage light-load management includes frequency foldback (active between 1.0–1.8 V FB) and burst mode (triggered below 0.7 V FB), both coordinated via the TIMER pin.

The controller uses a high-voltage (700 V) startup current source on the HV pin with brown-out detection (HVON = 107 V typ, HVOFF = 97 V typ) and intelligent X-cap discharge sequencing - initiating after ~32 TIMER cycles post-unplug, with alternating 16-cycle discharge/detection windows until VCC is reached.

Key Specifications

Pinout & Package

Package: SOIC8-7A (exposed pad not present; 7-pin functional count in 8-pin body, Pin 7 omitted).

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28630DR and ICE2QS03G, HFC0500GS uniquely combines fixed-frequency stability, programmable burst-mode thresholds, and autonomous X-cap discharge - enabling single-chip compliance with global no-load and safety standards without auxiliary circuitry.

Availability

HFC0500GS is available at Aetrix Electronics and suitable for AC/DC adapters, offline battery chargers, and LCD TV power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant green-mode operation.

Supply support for HFC0500GS 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.

HFC0500GS belongs to MPS's Green-Mode Flyback Controller product line, engineered specifically for ultra-low standby power and integrated safety features in universal-input offline SMPS.

FAQ

What is the purpose of the TIMER pin beyond soft start?

The TIMER pin serves four critical functions: (1) soft-start ramp generation via external capacitor; (2) frequency jitter modulation using internal 14 pF capacitor and 2.72 µA current source; (3) timing integration for OLP and brown-out protection (40 ms timeout); and (4) sequencing control for X-cap discharge cycles (32/16/48 pattern). All share the same pin to minimize external components while maintaining independent timing accuracy.

How does the X-cap discharge function eliminate external resistors?

HFC0500GS uses its HV pin as a smart switch: after AC removal, it waits ~32 TIMER cycles, then activates the internal HV current source for 16 cycles to discharge the X-cap. It then pauses 16 cycles to detect re-plug; if none, repeats with 48-cycle discharge. This eliminates constant-power bleed resistors - reducing no-load loss by up to 30 mW compared to passive solutions.

Can HFC0500GS operate without an auxiliary winding?

Yes - the HV pin provides a 700 V-rated startup current source that powers VCC until the auxiliary winding takes over. During brown-out or fault conditions, the HV source re-engages when VCC drops to 8.5 V (VCCON), enabling self-sustaining operation without auxiliary winding dependency - ideal for cost-sensitive, single-winding designs.

What defines the burst-mode hysteresis window?

Burst mode uses two distinct FB thresholds: entry at VBURL = 0.7 V (typ) and exit at VBURH = 0.8 V (typ), creating a 100 mV hysteresis window. This prevents oscillation near the threshold and ensures clean on/off transitions. The window is internally trimmed and temperature-compensated - no external components required.

How is overload protection implemented without secondary-side sensing?

OLP is primary-side sensed via FB voltage: when output overloads, opto-coupler current drops, raising FB above 3.7 V (VOLP). The TIMER pin then integrates this error for 40 ms (CTIMER = 47 nF). If sustained, the controller latches off - eliminating need for secondary-side current transformers or shunts while maintaining accurate power limiting across line variations.

Does HFC0500GS support continuous conduction mode (CCM)?

Yes - its internal 25 mV/μs slope compensation stabilizes current-mode control above 50% duty cycle, enabling reliable CCM operation across universal input ranges. Designers select primary inductance to target KP (ripple-to-peak ratio) of 0.6–0.8 for 85–265 VAC, ensuring stable regulation without subharmonic oscillation or external compensation.