STMicroelectronics VIPER25HN

Overview

VIPER25HN from STMicroelectronics is an integrated quasi-resonant off-line PWM controller with 800 V avalanche-rugged power MOSFET, adjustable current limiting via ZCD pin, hysteretic thermal shutdown at 150–160 °C, and <50 mW standby power at 265 Vac. It delivers up to 20 W in open-frame SMPS designs for auxiliary power supplies in LCD TVs, LED drivers, and utility meters.

For engineers reviewing the VIPER25HN datasheet, VIPER25HN pinout, VIPER25HN application, or VIPER25HN equivalent, key selection considerations include its 800 V drain-source breakdown voltage, valley-switching QR control architecture, dual overcurrent protection (primary + secondary), programmable overvoltage threshold (3.8–4.6 V), and SO-16N package with thermally enhanced DRAIN pins.

Technical Context

The VIPER25HN integrates a current-mode PWM controller, zero-current detection (ZCD) circuit for transformer demagnetization sensing, high-voltage startup generator sourcing from DRAIN, and dual-level overcurrent protection - one cycle-by-cycle (IDlim = 0.7 A typ.) and one latched second threshold (IDMAX = 1.2 A). Its quasi-resonant operation synchronizes MOSFET turn-on to valley points, reducing switching losses and EMI.

Brown-in/brown-out protection (VBRth = 0.45 V ±40 mV) enables robust input voltage monitoring, while burst-mode operation below VFBbm (0.6 V falling) achieves ultra-low standby consumption. The device features internal soft-start (tSS = 4.2 ms), safe auto-restart after fault removal, and self-supply via auxiliary winding with VDD regulation between 8.5–23.5 V.

Key Specifications

Pinout & Package

Package: SO-16N (16-pin small outline, thermally enhanced with exposed metal pad under DRAIN pins 13–16 for PCB heat sinking).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quasi-resonant off-line controller applications.

Compared with ICE2QS03G and LNK364PG, VIPER25HN offers superior integration (800 V switch + ZCD + OVP + thermal shutdown), lower standby power, and true valley-switching - making it optimal for compact, high-efficiency, no-el-cap designs demanding long lifetime and surge resilience.

Availability

VIPER25HN is available at Aetrix Electronics and suitable for adapter power supplies, auxiliary power for LCD/PDP TVs, no-electrolytic-capacitor LED drivers, and utility power meter SMPS requiring stable component supply and long-term industrial availability.

Supply support for VIPER25HN 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

VIPER25HN belongs to ST's VIPer™ high-voltage off-line converter family, engineered specifically for cost-sensitive, space-constrained AC/DC power supplies needing integrated HV switching, QR control, and comprehensive protection - targeting adapters, auxiliary supplies, and smart metering.

FAQ

What is the purpose of the ZCD pin in VIPER25HN?

The ZCD pin serves four integrated functions: zero-current detection for transformer demagnetization timing, adjustable current limit setting (via RLIM resistor), voltage feed-forward compensation (via RFF), and overvoltage protection sensing. It eliminates need for external current sense transformers or optocoupler-based OVP circuits - enabling single-winding auxiliary supply and simplified flyback design.

How does VIPER25HN achieve <50 mW standby power?

VIPER25HN achieves ultra-low standby power through burst-mode operation (activated when FB voltage falls below 0.6 V), deep UVLO hysteresis (VDDoff = 7.5–8.5 V), and reduced restart current (−0.6 mA) after fault. Its internal oscillator halts during burst cycles, and gate drive is disabled except for brief pulses - minimizing both switching and quiescent losses at no-load.

Can VIPER25HN replace VIPER22A in existing designs?

VIPER25HN is not a drop-in replacement for VIPER22A: it has higher BVDSS (800 V vs. 730 V), different ZCD functionality, tighter OVP tolerance (±0.4 V vs. ±0.6 V), and distinct soft-start timing (4.2 ms vs. 3.5 ms). Layout changes, RLIM/RFF resistor recalculations, and FB loop compensation adjustment are required - validation per DS6205 Rev 5 is mandatory.

What thermal design considerations apply to the SO-16N package?

The SO-16N package requires ≥100 mm² copper area (35 µm thick) under pins 13–16 (DRAIN) to achieve RTH-JA = 85 °C/W. Without this, junction temperature may exceed 150 °C at 12 W continuous load. Thermal vias to inner ground planes and minimal trace length between DRAIN pins and transformer primary are essential - per Figure 4 and Table 4 in DS6205.