STMicroelectronics VIPER27LDTR

Overview

VIPER27LDTR 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 - designed for low/medium-power AC-DC flyback converters in auxiliary power supplies.

For engineers reviewing the VIPER27LDTR datasheet, VIPER27LDTR pinout, VIPER27LDTR application, or VIPER27LDTR equivalent, this device delivers integrated high-voltage startup, burst-mode operation for energy compliance, hysteretic thermal shutdown, brown-out protection, and on-board soft-start - all in a SO-16 narrow package suitable for compact SMPS designs.

Technical Context

The VIPER27LDTR implements current-mode PWM control with cycle-by-cycle overcurrent protection, second-level OCP (hiccup mode), and digitally filtered overvoltage protection strobed during MOSFET off-time. Its oscillator features ±4 kHz frequency jittering at 250 Hz to reduce EMI peak emissions.

It integrates a high-voltage startup generator sourcing −3 mA into VDD from DRAIN above 80 V, transitions to self-supply via auxiliary winding, and includes UVLO (VDDon = 14 V, VDDoff = 8 V), thermal shutdown (TSD = 155 °C), and brown-out detection (VBRth = 0.45 V) with 50 mV hysteresis.

Key Specifications

Pinout & Package

Package: SO-16 narrow (SO16N), 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 LNK304P, VIPER27LDTR offers higher 800 V drain rating, adjustable current limit via CONT pin, and dedicated brown-out input - enabling more robust universal-input designs with fewer external components and tighter safety margins.

Availability

VIPER27LDTR is available at Aetrix Electronics and suitable for ATX auxiliary power supplies, consumer set-top box SMPS, and white goods auxiliary supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for VIPER27LDTR 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 analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

VIPER27LDTR belongs to ST's VIPer™ family of high-voltage off-line controllers - engineered specifically for compact, low-cost, energy-efficient AC-DC conversion in auxiliary and medium-power applications.

FAQ

What is the purpose of the CONT pin on VIPER27LDTR?

The CONT pin serves dual functions: it adjusts the cycle-by-cycle current limit threshold via an external resistor (RLIM), and acts as the input for overvoltage protection by monitoring the auxiliary winding voltage during MOSFET off-time. Its digital filtering and strobed sampling (2.2 µs delay) ensure noise immunity in high-dv/dt flyback environments.

How does VIPER27LDTR achieve <50 mW standby power?

It combines burst-mode operation (activated when FB voltage falls below 0.6 V), ultra-low quiescent current (270 µA in VDD-off state), and automatic transition to high-impedance mode during fault conditions. The 800 V MOSFET also eliminates external HV bias networks that contribute to no-load loss.

Can VIPER27LDTR be used in continuous conduction mode (CCM)?

No - VIPER27LDTR is optimized for discontinuous conduction mode (DCM) and quasi-resonant (QR) flyback topologies. Its 60 kHz fixed frequency, leading-edge blanking (300 ns), and current-mode architecture assume DCM operation; CCM use risks instability and inaccurate current sensing due to lack of slope compensation.

What thermal derating applies to VIPER27LDTR in SO-16 narrow package?

At TA = 60 °C, maximum power dissipation is 1.5 W (RthJA = 60 °C/W on standard FR4). Derating begins linearly above 60 °C ambient; junction temperature must stay ≤150 °C. For 12 W output designs, ≥100 mm² copper pour under DRAIN pins is required to maintain RthJP ≤25 °C/W.