STMicroelectronics VIPER38HD

Overview

VIPER38HD from STMicroelectronics is a high-voltage PWM current-mode flyback controller IC integrating an 800 V avalanche-rugged power MOSFET, embedded HV startup generator, and dual-level overcurrent protection (IDlim = 1.15 A typ, IDMAX = 1.7 A). It delivers up to 30 W peak power at 230 Vac in SO16 Narrow package, supports jittered 115 kHz operation (H-type), and achieves 30 mW no-load consumption - enabling compliance with stringent energy-saving standards in auxiliary power supplies.

For engineers reviewing the VIPER38HD datasheet, VIPER38HD pinout, VIPER38HD application, or VIPER38HD equivalent, key selection considerations include its integrated 800 V MOSFET breakdown rating, adjustable current limit via CONT pin, EPT-enabled sustained overload capability, and digital noise-filtered output overvoltage protection with 3.0 V threshold.

Technical Context

The VIPER38HD implements a current-mode PWM architecture with built-in oscillator jitter (±8 kHz modulation depth at 920 Hz center) to reduce EMI, and features two independent overcurrent protections: cycle-by-cycle limiting (IDlim adjustable down to 85% via external resistor) and second-level hiccup-mode shutdown (IDMAX = 1.7 A) for transformer saturation or secondary diode short-circuit events.

Its control loop uses a dedicated FB pin with three defined thresholds: burst-mode activation (VFBbm = 0.6 V), overload detection (VFBlin = 3.5 V), and shutdown (VFBolp = 4.8 V); the CONT pin configures either current limit scaling or output voltage monitoring with strobed, digitally filtered OVP (tSTROBE = 2 μs).

Key Specifications

Pinout & Package

Package: SO16 Narrow (10.3 mm × 7.6 mm, 1.27 mm pitch), thermally enhanced with DRAIN pins (13–16) connected to internal metal frame for direct PCB copper heat sinking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage flyback controller applications.

Compared with ICE3B0565J and LNK364PG, VIPER38HD provides superior surge resilience (800 V vs ≤725 V), deterministic overload handling (EPT + dual OCP), and certified EMI reduction (jitter + digital OVP), making it the only choice for industrial-grade auxiliary supplies requiring >20 W continuous output and <30 mW standby.

Availability

VIPER38HD is available at Aetrix Electronics and suitable for smart energy meter auxiliary supplies, industrial PLC adapters, home appliance standby power, and IoT gateway AC-DC converters requiring stable component supply across multi-year production cycles.

Supply support for VIPER38HD 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 silicon solutions for automotive, industrial, and power management applications.

VIPER38HD belongs to the VIPerPlus family of high-voltage offline controllers, engineered specifically for compact, low-component-count flyback power supplies targeting energy-efficient auxiliary rails in metering, industrial automation, and connected appliances.

FAQ

What is the maximum continuous output power achievable with VIPER38HD in an open-frame design?

VIPER38HD delivers up to 15 W continuous output power at 50 °C ambient in an open-frame configuration with adequate heat sinking, as verified in ST's DS10100 Rev 3 datasheet Table 1. This rating assumes SO16 Narrow package mounted on FR4 with 100 mm² copper pour, and accounts for thermal derating above 50 °C using RTH-JA = 85 °C/W.

How does the Extra Power Timer (EPT) function extend overload capability?

The EPT pin connects to an external capacitor that delays second-level OCP (IDMAX) activation for up to 2 seconds, allowing VIPER38HD to sustain 23–25 W peak loads - such as motor start-up surges in smart appliances. Once the capacitor charges to 4.0 V, the IC enters hiccup mode, preventing thermal runaway while maintaining system responsiveness.

Can VIPER38HD operate with a 12 V DC input instead of AC mains?

No - VIPER38HD is designed exclusively for offline AC-DC conversion with 85–265 Vac input rectified to bulk DC. Its HV startup circuit requires ≥60 V on the DRAIN pin to initiate charging of the VDD capacitor; applying 12 V DC directly to VDD bypasses protection circuits and violates absolute maximum ratings (VDD clamp = 23.5 V, but internal UVLO thresholds assume HV startup sequence).

What layout practices are mandatory for reliable thermal performance in SO16 Narrow package?

ST mandates connecting DRAIN pins (13–16) to ≥100 mm² of 35 µm copper on the primary-side PCB layer, with thermal vias to inner ground planes. The GND pins (1–2) must tie to the same low-impedance plane, and the VDD capacitor must be placed within 5 mm of pin 5 to minimize ringing. Failure to implement this results in junction temperature exceeding 150 °C at >10 W continuous load.