Monolithic Power Systems Inc. HFC0511GS-Z

Overview

HFC0511GS-Z 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 130kHz nominal switching frequency, reduces frequency to 27kHz under light load, enters burst mode for <30mW no-load consumption, and integrates X-cap discharge, brown-out detection, and over-power compensation - enabling compliance with EuP Lot 6 in notebook adapters and LCD monitors.

For engineers reviewing the HFC0511GS-Z datasheet, HFC0511GS-Z pinout, HFC0511GS-Z application, or HFC0511GS-Z equivalent, key selection criteria include its HV-start capability (700V breakdown), programmable soft-start via TIMER pin, dual-threshold burst mode (0.7V/0.8V FB), frequency jittering (±6.5% amplitude), and SOIC8-7A package compatibility with standard PCB layouts.

Technical Context

The HFC0511GS-Z implements a fixed-frequency current-mode architecture with integrated slope compensation (25mV/μs typical) to prevent sub-harmonic oscillation in CCM operation above 50% duty cycle. Its control loop uses feedback voltage (FB) to directly set primary peak current via a 2.8× division ratio (KFB2), enabling precise output regulation across universal input (85–265Vac).

Power management combines three adaptive modes: frequency foldback (21–27kHz min) below VFB = 1.8V, burst mode activation at VFB ≤ 0.7V with hysteresis to 0.8V, and HV-based X-cap discharge triggered after AC removal - all coordinated through the TIMER pin's multi-function circuitry including soft-start timing, OLP delay (40ms), and brown-out detection.

Key Specifications

Pinout & Package

Available in SOIC8-7A package: 8-pin, small-outline integrated circuit with 7mm × 5mm body, 1.27mm pitch, and exposed thermal pad (not electrically connected). Pin 1 marked by notch or dot; top-side marking includes "HFC0511" followed by lot code.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28632DR and ICE2QS03G, the HFC0511GS-Z uniquely integrates X-cap discharge, burst-mode hysteresis (0.7V/0.8V), and HV brown-out detection in a single SOIC8-7A package - enabling full safety certification (IEC62368-1) and regulatory compliance (EuP Lot 6, DOE Level VI) without external components.

Availability

HFC0511GS-Z is available at Aetrix Electronics and suitable for AC/DC notebook adapters, smartphone charging adapters, and LCD monitor power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant green-mode operation.

Supply support for HFC0511GS-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 over 20 years of expertise in DC/DC, AC/DC, and motor driver solutions.

The HFC0511 belongs to MPS's Green-Mode Flyback Controller product line, engineered specifically for ultra-low standby power, integrated safety features, and simplified compliance with global energy regulations in consumer and industrial offline power supplies.

FAQ

What is the minimum VCC hold-up time required to avoid brown-out during 50Hz AC dips?

The HFC0511GS-Z requires VCC capacitance sufficient to sustain operation for ≥10ms during line dips. Using Equation (3) with ICC(noswitch) = 700μA and Tinput = 20ms, a minimum 10μF VCC capacitor is recommended. A 22μF/25V ceramic+electrolytic parallel combination ensures reliable hold-up across temperature and aging.

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

The HV pin activates an internal 2.8mA current source 32 TIMER cycles after AC removal, discharging X-caps in timed 48-cycle bursts until voltage drops to VCC level. This replaces constant-loss 100kΩ/2W resistors, cutting no-load power by 120mW while maintaining IEC62368-1 touch-safe discharge within 1 second.

Can the HFC0511GS-Z operate in continuous conduction mode (CCM) at 230Vac input?

Yes - its internal slope compensation (25mV/μs typical) stabilizes current-mode control above 50% duty cycle. With KP = 0.8 ripple-to-peak ratio and proper transformer design, CCM operation is supported across universal input range, reducing RMS current and improving efficiency at full load.

What is the purpose of the two leading-edge blanking (LEB) times on the CS pin?

The HFC0511GS-Z uses dual LEB: 350ns for normal current limiting (VILIM) and 270ns for short-circuit protection (VSCP). This prevents false triggering from MOSFET switching spikes while ensuring fast SCP response - critical for protecting transformers and MOSFETs during output shorts.

How is over-power compensation adjusted for different input voltage ranges?

Over-power compensation is tuned by selecting a series resistor between CS and ground. The KOPC ratio (0.45μA/V) scales HV voltage into the CS node, allowing designers to match OLP trip points across 120V and 380V line peaks - narrowing power variation to ±3% instead of ±15% in uncompensated designs.

Does the HFC0511GS-Z support synchronous rectification?

No - the HFC0511GS-Z is a primary-side controller only and does not provide secondary-side gate drive signals. Synchronous rectification requires a separate SR controller (e.g., MP6908) or transformer auxiliary winding feedback; the HFC0511GS-Z's DRV pin drives only the primary-side MOSFET.

What thermal derating applies above 70°C ambient temperature?

With θJA = 96°C/W, the HFC0511GS-Z dissipates ≤1.3W at 25°C. At 70°C ambient, maximum allowable power drops to 0.83W (calculated as (150°C − 70°C)/96°C/W). Designers must reduce peak current or increase heatsinking to maintain thermal shutdown margin.