Monolithic Power Systems Inc. HF81GS-Z

Overview

HF81GS-Z from Monolithic Power Systems is a two-terminal X-capacitor bleeder IC that functions as a smart high-voltage switch in series with discharge resistors to eliminate standby power loss while ensuring automatic, safe X-cap discharge upon AC removal. It blocks current flow at 230 VAC (zero power loss), activates discharge when unplugged, and integrates a 1000 V internal JFET for differential surge immunity. Used in AC/DC front-ends requiring EuP Lot 6 or Energy Star V2.0 compliance.

For engineers reviewing the HF81GS-Z datasheet, HF81GS-Z pinout, HF81GS-Z application, or HF81GS-Z equivalent, key selection criteria include AC removal detection time (25 ms), saturation current (3.0 mA), supply current at 1000 V (15 µA), UVLO threshold (3.7 V), and SOIC8 package creepage (>4 mm) - all critical for safety-certified low-standby-power designs.

Technical Context

The HF81GS-Z operates without external bias, deriving power directly from the AC line via zero-crossing detection circuitry. Its internal latch and timer block trigger discharge only after sustained absence of zero crossings-ensuring reliable disconnection during operation and activation within 25 ms of AC removal.

It employs dual-pin redundancy per terminal (L1 and L2) to maintain functionality under single-point failure, and its 1000 V-rated internal JFET enables direct placement before or after the input fuse while meeting IEC 60950-1 creepage and surge immunity requirements.

Key Specifications

Pinout & Package

HF81GS-Z is housed in an industry-standard SOIC8 package with >4 mm creepage on PCB and dual-pin redundancy per terminal for safety-critical redundancy. Pin 1 is NC; Pins 2 & 3 are bonded to L1; Pins 6 & 7 are bonded to L2; remaining pins (1, 4, 5, 8) are NC.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar X-capacitor bleeder applications.

Compared with VIPer06XS and SIC8000, HF81GS-Z uniquely delivers zero standby loss, self-powered operation, and dual-pin safety redundancy - making it the only drop-in solution for certified low-standby-power AC/DC front-ends requiring automated X-cap discharge.

Availability

HF81GS-Z is available at Aetrix Electronics and suitable for energy-efficient AC/DC converters, EuP-compliant appliances, and telecom/server power supplies requiring stable component supply, long-term lifecycle support, and safety-certified X-capacitor discharge functionality.

Supply support for HF81GS-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 a focus on energy efficiency, miniaturization, and reliability across industrial, computing, and consumer markets.

The HF81 belongs to MPS's safety and protection IC product line, engineered specifically to replace lossy passive bleeder networks in AC/DC front-ends while enabling compliance with global energy regulations and safety standards.

FAQ

What is the maximum X-capacitor value supported by HF81GS-Z?

The HF81GS-Z supports up to 5 μF X-capacitors when paired with the corresponding total series resistance (150 kΩ) as specified in Table 1 of the datasheet. This value ensures the RC time constant remains ≤0.75 s, meeting IEC 60950-1 discharge requirements (voltage decay to ≤37% within 1 s) under worst-case tolerance conditions.

Can HF81GS-Z be placed before the input fuse?

Yes - HF81GS-Z is certified for placement before or after the input fuse per IEC 60950-1. When the X-capacitor exceeds 0.1 μF, it must be placed before the fuse to satisfy safety discharge requirements. Its double-pin L1/L2 terminals and 1000 V rating ensure robust operation in this configuration.

How does HF81GS-Z achieve zero standby power loss?

During AC operation, the HF81GS-Z actively blocks current through the external bleed resistors using its internal 1000 V JFET switch. This open-circuit state draws only 15 µA supply current at 1000 V, reducing resistive power loss to effectively zero - unlike fixed resistors that continuously dissipate watts.

What is the role of dual-pin bonding on L1 and L2?

Dual-pin bonding provides hardware-level redundancy: if one L1 or L2 pin fails open or shorts to the opposite terminal, the device either continues normal operation (open fault) or safely defaults to a shorted state equivalent to bypassing the HF81 (short fault), preserving system safety per single-point-failure testing in Table 3.

Does HF81GS-Z require external components to function?

Yes - HF81GS-Z requires two external bleed resistors (R1 and R2) connected in series between L1 and L2, sized per Table 1 based on X-capacitance. No external bias, timing capacitors, or control signals are needed - power and control are derived entirely from the AC line.

Is HF81GS-Z RoHS-compliant and lead-free?

Yes - HF81GS-Z is fully RoHS-compliant and lead-free, consistent with Monolithic Power Systems' green manufacturing policy. The SOIC8 package uses matte tin plating, and all materials meet JEDEC J-STD-020 moisture sensitivity level (MSL) 3 requirements for standard surface-mount assembly.