Monolithic Power Systems Inc. HF900GS-Z

Overview

HF900GS-Z from Monolithic Power Systems is a 900V integrated offline flyback switching regulator with monolithically integrated high-voltage MOSFET, peak-current-mode control, programmable switching frequency up to 300kHz, and burst-mode operation for <100mW standby power. It targets AC/DC power supplies in smart meters, industrial controls, and large appliances operating on unstable AC grids.

For engineers reviewing the HF900GS-Z datasheet, HF900GS-Z pinout, HF900GS-Z application, or HF900GS-Z equivalent, key selection criteria include its 900V drain rating, internal OTP co-integrated with the power FET, VCC UVLO hysteresis (3.6V typ), FB-triggered burst mode (0.5V entry / 0.7V exit), and FSET-programmable frequency with ±4% jittering for EMI reduction.

Technical Context

The HF900GS-Z implements peak-current-mode control with internal slope compensation (40 mV/μs) and dual leading-edge blanking (350 ns for current sense, 300 ns for SCP), enabling stable operation in discontinuous and continuous conduction modes up to 50% duty cycle. Its proprietary 900V monolithic process integrates the power switch and thermal shutdown circuitry on a single die.

It features active burst-mode control triggered by FB voltage (0.4–0.6V entry, 0.58–0.86V exit), time-based overload protection (82 ms delay at 100 kHz), and auto-recovery fault management for OVP (VCC >26.0V), SCP (VCS >1.42V), and PRO input overvoltage (>3.1V). The VCC supply transitions from DRAIN-startup current source to auxiliary winding after reaching VCCH (11.5–14.5V).

Key Specifications

Pinout & Package

HF900GS-Z is packaged in SOIC14-11, a thermally enhanced 14-pin surface-mount package with exposed pad (EP) for improved heat dissipation (θ_JA = 70°C/W, θ_JC = 35°C/W). Pin 13 is NC; pins 1, 2, 7, and 8 are internally bonded to GND for low-inductance grounding.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP100GZ and UCC28881DR, HF900GS-Z uniquely combines 900V integration, on-die OTP, and programmable jittering-enabling single-chip, certified-compliant solutions for harsh-grid and wireless-sensitive applications where reliability and EMI margin are non-negotiable.

Availability

HF900GS-Z is available at Aetrix Electronics and suitable for smart metering, industrial motor drive auxiliary supplies, and building automation controllers requiring stable component supply across extended product lifecycles and global regulatory certifications.

Supply support for HF900GS-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 leadership in integrated power stages and energy-efficient DC/DC conversion.

The HF900 product line delivers high-voltage offline regulators optimized for reliability-critical AC/DC conversion in utility infrastructure, industrial equipment, and home appliances operating on globally unstable grids.

FAQ

What is the maximum recommended continuous output power for HF900GS-Z in SOIC14-11 package?

The SOIC14-11 package has a thermal resistance θ_JA of 70°C/W and a maximum junction temperature of 150°C. At 25°C ambient, maximum continuous power dissipation is 1.45W. Accounting for conduction and switching losses, typical continuous output power is 8–10W with proper heatsinking and airflow. Higher power requires derating per ambient temperature and PCB copper area.

Can HF900GS-Z operate directly from 420VAC rectified input without capacitor stacking?

Yes. With a 900V drain rating and guaranteed 900V breakdown voltage (V_(BR)DSS), HF900GS-Z supports direct connection to a 420VAC full-wave rectified bus (≈590VDC peak). No capacitor stacking is required, unlike 600V or 650V alternatives - simplifying safety certification and improving long-term reliability.

How does the FSET pin set switching frequency, and what resistor value yields 100kHz?

FSET sets frequency via a resistor to GND using f_S ≈ 1/(R_FSET × 200pF) + 112.5kHz. For 100kHz, R_FSET ≈ 100kΩ yields 104kHz typical (90–118kHz min/max). The 1.23V reference ensures tight tolerance; ±1% resistor yields <1% frequency variation across temperature and unit-to-unit.

Does HF900GS-Z support both DCM and CCM operation, and how is CCM enabled?

Yes. Peak-current-mode control with internal slope compensation (40 mV/μs) allows stable operation in both DCM and CCM. CCM is enabled by selecting primary inductance and turns ratio such that duty cycle exceeds 50% at minimum input - slope compensation prevents subharmonic oscillation, verified per Equation (6) and (12) in the datasheet.

What protection features activate during a short-circuit event on the secondary side?

During secondary short-circuit, SOURCE voltage exceeds 1.42V (V_SC), triggering immediate shutdown within one switching cycle. The IC enters auto-recovery mode: VCC discharges to 5.3V (V_CCR), then recharges via DRAIN current source. Recovery occurs only after fault removal and VCC recharge to 13.0V (V_CCH), preventing latch-up.

Is the PRO pin intended only for input overvoltage protection?

No. While commonly used for input OVP (via resistor divider), PRO is a general-purpose protection input. It can monitor external signals such as NTC thermistor voltage for heatsink overtemperature, auxiliary rail undervoltage, or optocoupler fault detection - any condition exceeding 3.1V triggers shutdown with 0.2V hysteresis.

How does burst-mode operation reduce standby power, and what is the typical no-load consumption?

Burst mode disables switching when FB drops below 0.5V (e.g., light/no load), eliminating switching losses. The controller wakes periodically to sample FB; if >0.7V, it resumes PWM. This reduces no-load consumption to 65–85 mW depending on transformer design and output capacitance - meeting DOE Level VI and EU CoC Tier 2 requirements.