STMicroelectronics VIPER27LD

Overview

VIPER27LD from STMicroelectronics is an off-line high-voltage PWM controller IC with integrated 800 V avalanche-rugged N-channel MOSFET, 60 kHz fixed switching frequency (L-type), adjustable current limit via CONT pin, and <50 mW standby power at 265 Vac - used in auxiliary power supplies for ATX systems, DVD players, and white goods.

For engineers reviewing the VIPER27LD datasheet, VIPER27LD pinout, VIPER27LD application, or VIPER27LD equivalent, this device delivers integrated HV startup, burst-mode operation for energy compliance, hysteretic thermal shutdown, brown-out protection, and on-board soft-start - critical for low/medium-power AC-DC flyback converters requiring minimal external components and robust fault recovery.

Technical Context

The VIPER27LD implements current-mode PWM control with leading-edge blanking (300 ns), digitally filtered overvoltage protection strobed every 2.2 µs, and dual-level overcurrent protection - including cycle-by-cycle limiting (0.7 A typ.) and hiccup-mode second-level OCP (1 A). Its internal 800 V power section eliminates external HV start-up circuitry.

It features a jittered oscillator (±4 kHz spread at 250 Hz) to reduce EMI, a dedicated BR pin for brown-out detection (0.45 V threshold), and FB pin-based regulation with burst-mode activation below 0.6 V - enabling compliance with EU ErP Lot 6 and ENERGY STAR standby requirements.

Key Specifications

Pinout & Package

Package: SO16 narrow (SO-16N), surface-mount, with DRAIN pins (13–16) connected to internal metal frame for enhanced thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE2QS03G and LNK306P, VIPER27LD provides superior integration (HV startup, BR pin, strobed OVP), tighter standby performance (<50 mW), and design flexibility via CONT-pin current adjustment - making it optimal for cost-constrained, regulatory-compliant consumer auxiliary supplies.

Availability

VIPER27LD is available at Aetrix Electronics and suitable for ATX auxiliary power supplies, DVD player SMPS, and white goods control power circuits requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for VIPER27LD 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

VIPER27LD belongs to ST's VIPer™ family of high-voltage offline controllers - designed specifically for compact, low-cost, high-efficiency flyback converters in sub-25 W consumer and home appliance power supplies.

FAQ

What is the purpose of the BR pin on VIPER27LD?

The BR (Brown-out) pin monitors the rectified input voltage via a resistive divider. When voltage at this pin falls below 0.45 V (with 50 mV hysteresis), the IC disables switching to prevent unstable operation during low-line conditions. It can be grounded if unused, and draws only 7–12 µA hysteresis current - minimizing impact on divider accuracy.

How does the CONT pin function in VIPER27LD?

The CONT pin serves two roles: (1) adjusting cycle-by-cycle current limit via external RLIM resistor (0.7 A default, scalable down to ~0.3 A), and (2) sampling auxiliary winding voltage during MOSFET OFF time for digital overvoltage protection. It uses a 2.2 µs strobe window and four-consecutive-sample logic to reject noise while ensuring fast OVP response.

Can VIPER27LD operate without an auxiliary winding?

No - VIPER27LD 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 14 V, the HV generator turns off and the auxiliary winding must supply >25 mA to maintain regulation. Without it, VDD collapses below 8.5 V and the IC shuts down.

What thermal derating applies to VIPER27LD in SO16N package?

In SO16 narrow package mounted on standard FR4 with 100 mm² copper pour, VIPER27LD has RthJA = 50 °C/W. At 60 °C ambient, maximum continuous power is 1.5 W (per datasheet Table 5). For 20 W output designs, thermal design must ensure junction temperature stays ≤150 °C - typically requiring ≥4 cm² copper area under DRAIN pins and airflow or heatsink for sustained load.