Monolithic Power Systems Inc. EVHF900-P-00A

Overview

EVHF900-P-00A from Monolithic Power Systems is an off-line switching regulator evaluation board built around the HF900GPR flyback controller with integrated 900V MOSFET, delivering triple isolated outputs (13.5V/300mA, 8V/50mA, 8V/50mA) across 85–420VAC input for high-voltage metering power supplies. It implements frequency jittering, active burst-mode standby control, and comprehensive protection including OTP, OVP, SCP, OLP, and VCC UVLO.

For engineers reviewing the EVHF900-P-00A datasheet, EVHF900-P-00A pinout, EVHF900-P-00A application, or EVHF900-P-00A equivalent, this board serves as a validated reference design for EN55022-compliant, high-input-voltage, triple-output flyback power conversion in utility metering and three-phase industrial monitoring systems.

Technical Context

The EVHF900-P-00A implements a current-mode flyback topology using the HF900GPR IC, which integrates a 900V avalanche-rated MOSFET and supports programmable switching frequency up to 300kHz via external resistor R15. Its transformer (EE16 core, 2.5mH primary inductance) enables safe isolation between primary and secondary windings - meeting 4500VAC dielectric strength requirements.

Control loop stability is maintained via TL431-based optocoupled feedback (U1/U3), with R14/R17 setting output voltage and R21/R22 configuring peak current sensing. EMI compliance is achieved through CX1/CX2/X-capacitors, LX1 common-mode choke, and frequency jittering - eliminating discrete filtering beyond the board's single-sided PCB layout.

Key Specifications

Availability

EVHF900-P-00A is available at Aetrix Electronics and suitable for utility metering, industrial three-phase monitoring, smart grid sensor nodes, and high-input-voltage AC/DC conversion requiring stable component supply, regulatory-compliant reference designs, and rapid prototyping validation.

Supply support for EVHF900-P-00A 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-efficient, high-voltage, and thermally optimized power management solutions.

The HF900 product line targets ultra-high-input-voltage offline flyback applications - specifically designed for utility-grade electricity meters, industrial AC-powered sensors, and equipment requiring >400VAC tolerance and reinforced isolation.

FAQ

What is the maximum input voltage the EVHF900-P-00A can safely handle?

The board is rated for continuous operation from 85VAC to 420VAC at 60Hz. Its transformer provides 4500VAC isolation between primary and secondary, and the integrated HF900GPR IC features a 900V MOSFET with avalanche rating - enabling reliable operation even during transient overvoltage events typical in utility distribution networks.

Can the 8V outputs be combined to increase current capability?

No - the two 8V outputs are galvanically isolated from each other and from the 13.5V rail, as confirmed by transformer winding diagram (N3/N4/N5 separate secondaries) and schematic (independent rectification D6/D9). Combining them would violate isolation barriers and compromise safety certification and EMC performance.

Does the board support synchronous rectification?

No - the secondary-side rectification uses diodes only: MBRS3200T3G Schottky (13.5V rail) and 1N4007 (8V rails). The HF900GPR does not provide gate drive signals for synchronous FETs; its architecture relies on diode-based flyback with slope compensation and leading-edge blanking for stability.

How is EMI compliance achieved without external filters?

Conducted EMI suppression is implemented on-board via CX1/CX2 X-capacitors (0.22μF total), LX1 common-mode choke (24mH), and frequency jittering in the HF900GPR IC. These elements meet EN55022 Class B limits across full input range - verified per Rev. 1.1 test report and confirmed by absence of external filter components in BOM and schematic.

Is the board agency-certified for safety standards?

No - the documentation explicitly states: "the engineering prototype has not been agency approved." It is intended for lab evaluation only. Users must implement isolation transformers during testing and perform full safety certification (e.g., UL/IEC 62368-1) on final end-equipment incorporating this reference design.

What is the role of the PRO pin on the HF900GPR IC?

The PRO pin is a dedicated protection configuration terminal that enables auto-restart after fault conditions (e.g., OLP, OTP). When pulled high via internal pull-up, it sets restart delay and latching behavior - allowing system-level customization of fault recovery without external circuitry, as implemented via R18 and C14 on the board.