STMicroelectronics VIPER12AS-E

Overview

VIPER12AS-E from STMicroelectronics is a monolithic high-voltage offline SMPS primary switcher integrating a 730 V avalanche-rated power MOSFET and current-mode PWM controller in SO-8 package. It delivers up to 8 W at 195–265 Vac input, features fixed 60 kHz switching, 9–38 V VDD operating range, and built-in overtemperature, overcurrent, and overvoltage protection with auto-restart-used in battery charger adapters and TV standby supplies.

For engineers reviewing the VIPER12AS-E datasheet, VIPER12AS-E pinout, VIPER12AS-E application, or VIPER12AS-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 rectangular U-I output capability for dual voltage/current regulation in Li-ion charging circuits.

Technical Context

The VIPER12AS-E implements a current-mode control loop where peak drain current is directly set by feedback current (IFB) into the FB pin, with gain GID = 320 A/A and internal 0.23 V reference comparator. Its oscillator operates at 60 kHz ±10% across 0–100 °C and VDD = 9–35 V, enabling stable flyback operation without external timing components.

Startup relies on an internal high-voltage current source connected to the DRAIN pin, charging the VDD capacitor until VDD reaches 14.5 V (VDDon); shutdown occurs at 8 V (VDDoff) with 6.5 V hysteresis. Protection includes latch-free auto-restart on overtemperature (TSD = 140–170 °C), overcurrent (IDlim = 0.4 A typ), and overvoltage (VDDovp = 42 V typ).

Key Specifications

Pinout & Package

Package: SO-8, ECOPACK®-compliant, surface-mount, 1.27 mm pitch, 5.0 × 4.0 × 1.75 mm body height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE2A0565Z and LNK304P, VIPER12AS-E uniquely combines integrated HV start-up, current-mode FB control with optocoupler interface, and auto-burst mode - making it optimal for cost-sensitive, low-noise, dual-regulation offline supplies under 8 W.

Availability

VIPER12AS-E is available at Aetrix Electronics and suitable for battery charger adapters, TV standby power supplies, and auxiliary motor control supplies requiring stable component supply and long-term industrial availability.

Supply support for VIPER12AS-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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

VIPER™ is ST's proprietary family of high-voltage offline SMPS controllers targeting cost-sensitive, low-to-medium power AC-DC conversion with integrated MOSFETs and minimal external components.

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, per ST application guidance. Lower values risk premature VDD collapse before auxiliary energy transfer, causing startup failure-especially at low input voltages (85 Vac). The capacitor must be placed within 5 mm of VDD and SOURCE pins to minimize parasitic inductance.

Can VIPER12AS-E regulate both output voltage and current simultaneously?

Yes-when paired with a dual-error amplifier like TSM101 on the secondary side, the FB pin's current-mode architecture enables combined CV/CC regulation. The resulting rectangular U-I output characteristic is confirmed in Figure 4 of the datasheet and validated in battery charger reference designs delivering defined charge current until voltage threshold is reached.

Does VIPER12AS-E require an external current-sense resistor?

No-internal current sensing eliminates the need for an external shunt. Peak drain current is controlled by FB pin current (IFB) interacting with the MOSFET's internal current-sense ratio (GID = 320 A/A) and 0.23 V comparator reference. This reduces power loss and PCB area versus discrete sense-resistor solutions.

How does thermal shutdown behave during sustained overload?

At junction temperature ≥170 °C, the device enters thermal shutdown and halts switching. After cooling by ≥40 °C (to ≤130 °C), it automatically restarts-no manual reset required. This auto-restart behavior is documented in Section 7 (Thermal data) and Figure 13, ensuring safe operation during intermittent overloads without latch-up.