STMicroelectronics VIPER26LDTR

Overview

VIPER26LDTR from STMicroelectronics is a high-voltage offline PWM controller IC integrating an 800 V avalanche-rugged power MOSFET, current-mode control, and embedded HV startup circuitry. It delivers up to 20 W in open-frame designs at 50 °C ambient, supports flyback/buck/buck-boost topologies, and achieves <30 mW no-load input power at 230 VAC - enabling compliance with stringent energy-saving standards such as EU CoC Tier 2 and DOE Level VI in auxiliary power supplies for appliances and LED drivers.

For engineers reviewing the VIPER26LDTR datasheet, VIPER26LDTR pinout, VIPER26LDTR application, or VIPER26LDTR equivalent, this device requires attention to DRAIN thermal pad layout, LIM pin resistor selection for current limit tuning, FB/COMP loop compensation in isolated vs. non-isolated configurations, and burst-mode behavior under light load.

Technical Context

The VIPER26LDTR implements a fixed-frequency current-mode PWM controller with jittered oscillator (±4 kHz around 60 kHz) to reduce EMI filter cost, integrated transconductance error amplifier referenced to 3.3 V, and cycle-by-cycle OCP via internal SenseFET. Its HV startup circuit draws current directly from DRAIN to charge VDD until VDDon (12–14 V) is reached, then disables to minimize quiescent consumption.

Thermal protection uses hysteretic shutdown (TSD = 150–160 °C, THYS = 30 °C), while soft-start (tSS = 8.5 ms) progressively raises the drain current limit to prevent transformer saturation. The COMP pin serves dual roles: output of the internal E/A in non-isolated designs, or optocoupler-driven control node in isolated feedback - requiring FB shorted to GND to disable the E/A.

Key Specifications

Pinout & Package

Package: SO16 narrow (SO16N), thermally enhanced with exposed DRAIN pins (pins 13–16) for PCB copper heat spreading. Mounting on 100 mm² Cu (35 µm) reduces R_TH-JA to 85 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar offline PWM controller applications.

Compared with ICE2QS03G and LNK364PG, VIPER26LDTR uniquely combines 800 V ruggedness, jittered 60 kHz operation, and a dedicated LIM pin - enabling lower EMI filter cost, stricter standby compliance, and precise current limit calibration in compact auxiliary supplies.

Availability

VIPER26LDTR is available at Aetrix Electronics and suitable for appliance auxiliary supplies, smart metering systems, and LED driver designs requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for VIPER26LDTR 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.

The VIPER™ family targets highly integrated, low-component-count offline SMPS controllers - designed specifically to simplify auxiliary and low-power primary-side regulation while meeting global energy efficiency mandates.

FAQ

What is the function of the LIM pin on VIPER26LDTR?

The LIM pin is a current-sink input that adjusts the drain current limit (IDLIM) downward from its default 0.7 A value. Connecting an external resistor between LIM and GND sets the sunk current, which linearly scales IDLIM down to ~0.3 A. This enables precise OCP tuning for transformer saturation margin and short-circuit energy limiting - critical in flyback designs with variable output loads.

How does VIPER26LDTR achieve <30 mW no-load consumption?

VIPER26LDTR achieves ultra-low no-load power through three mechanisms: (1) HV startup circuit disables after VDD reaches 12–14 V, eliminating continuous high-voltage bias current; (2) burst mode activates when VCOMP falls below 1.1 V, reducing average switching frequency to hundreds of Hz; (3) internal logic enters ultra-low-current state (IDD0 ≤ 0.6 mA) during burst OFF periods - collectively cutting total input power to <30 mW at 230 VAC.

Can VIPER26LDTR be used in isolated flyback designs without an auxiliary winding?

Yes - VIPER26LDTR supports auxiliary-winding-less operation using its integrated HV startup current source. During initial power-up, the DRAIN pin supplies charging current to the VDD capacitor until VDDon is reached. Once running, the device can sustain operation from residual leakage inductance energy or minimal auxiliary coupling, though a dedicated auxiliary winding is recommended for robustness under all line/load conditions.

What thermal design considerations apply to the DRAIN pins?

The DRAIN pins (13–16) are mechanically tied to the MOSFET die pad and serve as primary thermal conduction paths. For SO16N packaging, STMicroelectronics specifies mounting on ≥100 mm² of 35 µm copper to achieve R_TH-JA = 85 °C/W. Thermal vias under the DRAIN pads and connection to inner-layer ground planes further reduce junction-to-ambient resistance - essential to maintain TJ ≤ 150 °C at full 20 W output in open-frame configurations.