Monolithic Power Systems Inc. HF81GS-P

Overview

HF81GS-P 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 through bleed resistors at 230 VAC (zero power loss), activates discharge when AC is 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-P datasheet, HF81GS-P pinout, HF81GS-P application, or HF81GS-P 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 ultra-low no-load power and safety-certified designs.

Technical Context

The HF81GS-P 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 (e.g., plug removal), enabling precise timing control independent of input voltage magnitude.

It uses dual-pin redundancy per terminal (L1 and L2) to maintain functionality under single-point failure, and its 1000 V-rated internal JFET ensures robust operation across 110–410 VAC inputs while meeting IEC 60950-1 clearance and creepage requirements.

Key Specifications

Pinout & Package

HF81GS-P is housed in an industry-standard SOIC8 package with >4 mm creepage distance on PCB and molded body, compliant with JEDEC MS-012 AA. Pin assignment features dual-redundant terminals for functional safety: L1 (pins 2 & 3), L2 (pins 6 & 7), and four NC pins (1, 4, 5, 8).

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-P uniquely delivers zero-power standby operation, deterministic 25 ms detection, and certified dual-pin fault tolerance - making it optimal for high-reliability, safety-critical, and ultra-low-power AC/DC front-ends.

Availability

HF81GS-P is available at Aetrix Electronics and suitable for energy-efficient AC/DC adapters, EuP Lot 6–compliant appliances, and server power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing for safety-critical designs.

Supply support for HF81GS-P 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 two decades of leadership in DC/DC converters, LED drivers, and AC/DC solutions.

The HF81GS-P belongs to MPS's safety-critical power management product line, engineered specifically to replace lossy discharge resistors in X-capacitor circuits while meeting global safety standards including IEC 60950-1 and EN 60335-1.

FAQ

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

The HF81GS-P supports up to 5 μF X-capacitors when paired with the corresponding total series resistance (150 kΩ) from Table 1. This configuration delivers 464 mW of power saving at 265 VAC and ensures discharge to ≤37% within 1 second per safety standards.

Does HF81GS-P require a ground connection?

No. HF81GS-P has no ground pin and operates entirely between L1 and L2. This architecture provides high common-mode surge immunity and simplifies PCB layout in isolated front-end designs, eliminating grounding conflicts in double-insulated systems.

How does HF81GS-P behave during a single-pin open failure?

Due to dual-pin redundancy (pins 2 & 3 for L1; pins 6 & 7 for L2), disconnecting one L1 or L2 pin has no effect on discharge functionality. The device continues operating normally - a verified behavior documented in Table 3 of the datasheet for IEC 60950-1 compliance.

Can HF81GS-P be placed after the input fuse?

Yes - HF81GS-P is certified for use both before and after the input fuse. When the X-capacitor exceeds 0.1 μF, placement before the fuse is required to meet safety standards; HF81GS-P's dual-pin design and 1000 V rating make it suitable for either location.

What is the recommended PCB layout for surge immunity?

Place HF81GS-P physically adjacent to the MOV - either directly underneath the X-capacitor (MOV Position 1) or on the same side as the MOV (Position 2). Minimize trace length between HF81GS-P and MOV to reduce inductive voltage drop during 1.5–2 kV surges, as specified in Figure 2 and layout guidance on page 8.

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

Yes. HF81GS-P is fully RoHS-compliant and lead-free, consistent with MPS's green manufacturing policy. Full compliance documentation, including substance declarations and test reports, is available on the Monolithic Power Systems Quality Assurance webpage.