STMicroelectronics VIPER27HD

Overview

VIPER27HD from STMicroelectronics is an off-line high-voltage AC-DC converter IC integrating an 800 V avalanche-rugged N-channel power MOSFET, current-mode PWM controller, adjustable cycle-by-cycle overcurrent protection (IDlim = 0.7 A typ.), 115 kHz fixed switching frequency with ±8 kHz jitter, and <50 mW standby power at 265 Vac - used as primary-side controller in flyback converters for auxiliary power supplies in consumer electronics.

For engineers reviewing the VIPER27HD datasheet, VIPER27HD pinout, VIPER27HD application, or VIPER27HD equivalent, key selection considerations include its SO16 narrow package thermal performance (RthJA = 60 °C/W on standard FR4), integrated HV startup (VDRAIN_START = 80 V typ.), burst-mode operation below VFBbm = 0.6 V, and dual-level OCP with hiccup mode recovery.

Technical Context

The VIPER27HD implements a current-mode flyback controller with internal SenseFET-based drain current sensing, enabling precise cycle-by-cycle current limiting via the CONT pin (adjustable IDlim range: 0.66–0.74 A at 25 °C). Its oscillator delivers fixed 115 kHz operation with 250 Hz spread-spectrum frequency modulation (±8 kHz depth) to reduce EMI peak emissions without external filtering.

It integrates brown-out protection (VBRth = 0.45 V, 50 mV hysteresis), hysteretic thermal shutdown (TSD = 155 °C typ., THYST = 30 °C), and auto-restart after fault clearance with reduced restart current (IDDch = 0.6 mA vs. 3 mA normal start-up), ensuring safe recovery under overload, OVP, or overtemperature conditions.

Key Specifications

Pinout & Package

VIPER27HD is housed in a SO16 narrow (SO-16N) surface-mount package with exposed DRAIN pins (13–16) connected to the metal frame for enhanced thermal dissipation (RthJA = 60 °C/W on 100 mm² Cu).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE3B0565J and LNK306PN, VIPER27HD provides superior integration (800 V rating, adjustable OCP/OVP, burst-mode, brown-out), tighter thermal management (hysteretic shutdown), and lower standby power - making it optimal for space-constrained, high-reliability consumer auxiliary supplies.

Availability

VIPER27HD is available at Aetrix Electronics and suitable for ATX auxiliary power supplies, set-top box SMPS, and DVD player adapters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for VIPER27HD 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 analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

VIPER27HD belongs to ST's VIPer™ family of high-voltage offline controllers - engineered specifically for cost-sensitive, low-to-medium power AC-DC conversion in consumer auxiliary and embedded power applications.

FAQ

What is the maximum continuous output power achievable with VIPER27HD in an open-frame design?

VIPER27HD supports up to 12 W continuous output power in open-frame configurations at 50 °C ambient with adequate heatsinking, as verified in ST's reference design (Doc ID 15133, Table 2). This assumes proper PCB copper area under DRAIN pins and SO16N thermal resistance of 60 °C/W on standard FR4.

How does the CONT pin function in overvoltage protection mode?

In OVP mode, the CONT pin samples the auxiliary winding voltage during MOSFET OFF time. When this voltage exceeds VOVP = 3.0 V for four consecutive cycles (with 2.2 µs strobe delay), the IC enters auto-restart. The same pin also adjusts current limit via external resistor RLIM - dual functionality requires careful RC network design per Figure 27 in the datasheet.

Can VIPER27HD operate without an auxiliary winding?

No - VIPER27HD requires an auxiliary winding to sustain VDD after startup. The internal HV startup current (−3 mA) only charges the VDD capacitor initially; once VDD reaches VDDon = 14 V, the HV generator disables and the IC relies on energy from the auxiliary winding. Omitting it causes immediate shutdown after startup.

What is the purpose of the BR pin, and how should it be configured?

The BR pin implements brown-out protection by monitoring a scaled version of the bulk DC voltage. It triggers non-latching shutdown when voltage falls below VBRth = 0.45 V (with 50 mV hysteresis). If unused, ST recommends connecting BR directly to GND to disable the function - leaving it floating may cause erratic behavior due to noise coupling.