STMicroelectronics VIPER12AS

Overview

VIPER12AS from STMicroelectronics is a high-voltage, current-mode PWM controller with integrated 730 V Power MOSFET in SO-8 package, designed for off-line SMPS primary-side switching. It operates at fixed 60 kHz, supports 9–38 V VDD supply, and delivers up to 8 W (wide-range AC) or 13 W (European AC) output power in battery charger adapters, TV standby supplies, and auxiliary motor control power rails.

For engineers reviewing the VIPER12AS datasheet, VIPER12AS pinout, VIPER12AS application, or VIPER12AS equivalent, key selection criteria include its integrated HV start-up current source, VDD hysteresis (6.5 V typ), thermal shutdown at 170 °C, and FB-pin current-sensing architecture enabling precise peak-current limiting and burst-mode operation under light load.

Technical Context

The VIPER12AS integrates a 730 V vertical Power MOSFET and current-mode PWM controller on a single die, eliminating external gate drivers and bootstrap components. Its internal high-voltage start-up current source charges the VDD capacitor directly from the DRAIN pin, enabling self-biased operation without auxiliary winding during initial startup.

Feedback is implemented via current-mode sensing at the FB pin (0–1 V range), where drain peak current is linearly controlled by injected FB current (GID = 320 typ). Protection features include auto-restart overvoltage lockout (VDDovp = 42 V), undervoltage hysteresis (VDDon/VDDoff = 14.5 V / 8 V), and thermal shutdown with 40 °C hysteresis.

Key Specifications

Pinout & Package

SO-8 surface-mount package (JEDEC MS-012AC), 5.0 mm × 6.0 mm body, 1.27 mm pitch, with exposed DRAIN pads thermally connected to pins 1, 2, 3, and 4 for enhanced heat dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side SMPS controller applications.

Compared with LNK304P and ICE2QS03G, VIPER12AS offers superior integration (HV MOSFET + start-up source), tighter VDD hysteresis control, and lower system-level component count for sub-13 W offline SMPS-making it optimal for space-constrained, low-BOM-cost adapters and standby supplies.

Availability

VIPER12AS is available at Aetrix Electronics and suitable for battery charger adapters, TV standby power supplies, and auxiliary motor control rails requiring stable component supply across long-lifecycle industrial and consumer programs.

Supply support for VIPER12AS 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

VIPER12AS belongs to ST's VIPer™ family of high-voltage SMPS primary controllers, engineered specifically for compact, low-component-count offline power supplies targeting <15 W applications with stringent cost and size constraints.

FAQ

What is the maximum continuous output power achievable with VIPER12AS in a universal-input flyback design?

The VIPER12AS delivers up to 8 W with 85–265 Vac input and 13 W with 195–265 Vac input, as verified in ST's AN2357 reference design. Output power is limited by thermal resistance (55 °C/W junction-to-ambient in SO-8) and peak current capability (0.4 A), not switching frequency. Derating is required above 50 °C ambient.

Can VIPER12AS operate without an auxiliary winding for VDD supply?

Yes - its integrated high-voltage start-up current source draws from the DRAIN pin to charge the VDD capacitor, enabling operation with no auxiliary winding during initial startup. However, a minimal auxiliary winding is still required for sustained regulation once VDD reaches 14.5 V, as the start-up source disables at that threshold.

How does the FB pin current control affect loop stability in optocoupler-based feedback?

The FB pin presents a 1.2 kΩ input impedance and responds linearly to injected current (0–0.9 mA), allowing standard TL431 + optocoupler circuits to achieve phase margin >45° with proper compensation. The internal blanking time (500 ns) and minimum on-time (700 ns) constrain low-frequency gain but simplify Type II compensation network design.

Is VIPER12AS RoHS-compliant and halogen-free?

Yes - VIPER12AS (SO-8 package) is manufactured per RoHS Directive 2011/65/EU and meets JEDEC JS709B halogen-free requirements (<900 ppm bromine, <900 ppm chlorine, total ≤1500 ppm). ST's official device summary document (Doc ID 11255) confirms Pb-free matte tin lead finish and green molding compound.