Monolithic Power Systems Inc. HF500GS-7-Z

Overview

HF500GS-7-Z from Monolithic Power Systems is a fixed-frequency, current-mode flyback regulator IC integrating a 700V/12Ω MOSFET and self-supply startup circuitry in a single SOIC8-7B package. It delivers up to 7W output power at 230Vac input with external VCC supply, supports frequency jittering (±6.5% amplitude), operates down to 25kHz minimum switching frequency in foldback mode, and enters burst mode below 0.7V FB for <300mW standby consumption - deployed in low-power AC/DC adapters and auxiliary supplies.

For engineers reviewing the HF500GS-7-Z datasheet, HF500GS-7-Z pinout, HF500GS-7-Z application, or HF500GS-7-Z equivalent, key selection criteria include integrated 700V MOSFET R_DS(on), self-supply capability eliminating auxiliary winding, over-power line compensation via B/O pin, timer-based OLP with 32ms delay, and thermal shutdown with 25°C hysteresis.

Technical Context

The HF500GS-7-Z implements current-mode control with built-in slope compensation (18–31 mV/μs) to prevent subharmonic oscillation above 50% duty cycle in CCM operation. Its oscillator uses a triangular TIMER voltage (2.8–3.2V) modulated by an internal capacitor charging current to generate 65kHz ±6.5% jittered switching frequency.

Over-power compensation is achieved by adding a B/O-voltage-dependent offset (0–270mV) to the current-sense threshold, making OLP trip point independent of input voltage. The IC transitions from fixed-frequency (65kHz) → frequency foldback (25kHz min) → burst mode based on FB voltage thresholds: V_FB(FOLD) = 1.8V, V_BURL = 0.7V, V_BURH = 0.8V.

Key Specifications

Pinout & Package

HF500GS-7-Z is housed in a SOIC8-7B package: 8-lead narrow-body SOIC with pin 3 omitted (mechanical dummy), exposing no thermal pad. Pin spacing is 1.27mm, body width 3.9mm, and maximum height 1.75mm - compatible with standard SOIC reflow profiles and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP6004GQ-Z and UCC28740DR, HF500GS-7-Z uniquely combines self-supply, over-power compensation, and integrated slope compensation - reducing component count by 4–6 parts while enabling robust universal-input operation without external stability networks or auxiliary windings.

Availability

HF500GS-7-Z is available at Aetrix Electronics and suitable for home appliance auxiliary supplies, low-power AC/DC adapters, and industrial sensor node power converters requiring stable component supply across extended product lifecycles.

Supply support for HF500GS-7-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 integrated power solutions for consumer, industrial, and automotive markets.

The HF500GS-7-Z belongs to MPS's HF-series fixed-frequency flyback controllers, designed specifically for cost-sensitive, low-power offline SMPS where BOM reduction, EMI compliance, and universal-input robustness are critical.

FAQ

What is the purpose of the B/O pin on HF500GS-7-Z?

The B/O pin serves three functions: brown-in/brown-out detection (0.9V thresholds), input over-voltage protection (4.5V trigger), and over-power compensation (voltage-dependent FB offset). When pulled above 6V, all functions disable - allowing simplified operation if line monitoring is unnecessary.

Can HF500GS-7-Z operate without an auxiliary winding?

Yes. Its internal 3.6mA high-voltage start-up current source draws from the DRAIN pin to charge the VCC capacitor, enabling full self-supply operation. This eliminates the auxiliary winding, reducing BOM cost and PCB area - confirmed in typical application schematics with VCC supplied solely from DRAIN.

How does frequency jittering improve EMI performance?

Frequency jittering modulates the 65kHz switching frequency by ±6.5% with a 3.7ms period, spreading spectral energy across a ~4.2MHz band. This reduces peak conducted EMI amplitudes by up to 8dB versus fixed-frequency operation - easing compliance with EN55032 Class B limits without added filtering.

What triggers the latch-off OLP protection?

OLP activates when FB voltage exceeds 3.7V for 32ms (set by 47nF TIMER capacitor), indicating sustained overload. The IC then latches off until VCC drops below 2.5V - requiring full power cycle reset. This prevents thermal runaway while ignoring brief transients during startup or load steps.

What is the minimum switching frequency in foldback mode?

The HF500GS-7-Z reduces switching frequency to 25kHz minimum (typical) during light-load foldback, freezing peak current at 0.68V on SOURCE. This balances reduced switching loss against audible noise - verified in Figure 4 of the datasheet showing f_OSC(min) = 25kHz at V_FB = 1.0V.

How is thermal shutdown implemented?

Thermal shutdown triggers at 150°C junction temperature and auto-restarts when temperature falls to 125°C (25°C hysteresis). During shutdown, the VCC UVLO lower threshold drops from 7V to 5.3V to maintain latch condition - preventing erratic restarts until thermal recovery is complete.

What value of TIMER capacitor sets the OLP delay?

A 47nF capacitor on the TIMER pin yields the specified 32ms OLP delay, as confirmed in the Electrical Characteristics table (T_OLP = 32ms @ C_TIMER = 47nF). Changing capacitance linearly scales delay - e.g., 23.5nF halves it to 16ms.