STMicroelectronics VIPER12ASTR-E

Overview

VIPER12ASTR-E from STMicroelectronics is a monolithic high-voltage offline SMPS primary switcher integrating a current-mode PWM controller and 730 V avalanche-rated power MOSFET in one SO-8 package. It delivers up to 8 W at 195–265 Vac input, features fixed 60 kHz switching, 9–38 V wide VDD operating range, and built-in overtemperature/overcurrent/overvoltage protection with auto-restart - enabling compact, low-cost auxiliary supplies for TV standby circuits.

For engineers reviewing the VIPER12ASTR-E datasheet, VIPER12ASTR-E pinout, VIPER12ASTR-E application, or VIPER12ASTR-E equivalent, key selection considerations include its integrated HV start-up current source, FB pin current-sensing architecture (0–1 V effective range), thermal shutdown at 140–170 °C, and SO-8 package's 55 °C/W junction-to-ambient thermal resistance under standard PCB layout.

Technical Context

The device implements current-mode control via an internal transconductance amplifier comparing sensed drain current (scaled by GID = 320) against a 0.23 V reference, enabling precise peak-current limiting. Its feedback pin accepts 0–0.9 mA current input - not voltage - and triggers shutdown if IFB exceeds 0.9 mA.

Startup relies on an internal high-voltage current source connected to DRAIN, charging the external VDD capacitor until VDD reaches 13–16 V (VDDon); operation halts when VDD drops below 7–9 V (VDDoff), with 5.8–7.2 V hysteresis. Overvoltage protection latches at 38–46 V on VDD and auto-resets after decay to VDDoff.

Key Specifications

Pinout & Package

Available in RoHS-compliant SO-8 package (5.0 × 4.0 × 1.75 mm, 1.27 mm pitch), with exposed DRAIN pads thermally connected to pins 1–4 and 5–8 for enhanced heat dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar offline SMPS primary switcher applications.

Compared with ICE2A265 and LNK304P, VIPER12ASTR-E provides integrated HV start-up, VDD overvoltage auto-restart, and wider 9–38 V supply tolerance - reducing component count and improving reliability in cost-sensitive, space-constrained auxiliary supplies.

Availability

VIPER12ASTR-E is available at Aetrix Electronics and suitable for battery charger adapters, TV standby supplies, and auxiliary motor drive power rails requiring stable component supply across industrial and consumer production programs.

Supply support for VIPER12ASTR-E 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/mixed-signal products for automotive, industrial, and consumer markets.

VIPER™ is ST's dedicated family of integrated HV converters targeting low-power offline SMPS applications - optimized for simplicity, safety, and compliance in cost-sensitive AC/DC adapter and auxiliary supply designs.

FAQ

What is the minimum recommended VDD capacitor value for reliable startup?

A 100 nF ceramic capacitor is sufficient when using forward-biased auxiliary winding supply, as specified in ST Application Note AN2359. This value ensures adequate energy storage during the startup interval before auxiliary power becomes active, preventing premature VDD collapse and failed startup under worst-case line and load conditions.

Can VIPER12ASTR-E operate with a resistive feedback network instead of an optocoupler?

No - the FB pin requires current injection (0–0.9 mA), not voltage bias. A resistive divider alone cannot provide controlled current sourcing/sinking; it must interface with a current-output device like an optocoupler LED or TSM101-based error amplifier to achieve regulation and protection functionality.

How does the device behave during output short-circuit conditions?

Under short-circuit, FB current rises rapidly, triggering immediate shutdown when IFB exceeds 0.9 mA. The device enters auto-restart mode: it remains off until VDD decays below VDDoff (~8 V), then re-attempts startup. This cycle repeats at ~16% duty cycle (DRST), limiting average power dissipation and preventing thermal runaway.

Is the SO-8 package thermally adequate for 8 W operation at 265 Vac?

Yes - with a standard single-sided FR4 PCB having ≥200 mm² copper pour connected to all DRAIN pins, the SO-8 achieves RthJA = 55 °C/W. At 8 W output with typical 65% efficiency (12.3 W input), junction temperature rise is ~678 °C·W × 0.0123 W ≈ 83 °C above ambient - well within the 150 °C case rating and 170 °C thermal shutdown threshold.