STMicroelectronics VIPER25HDTR

Overview

VIPER25HDTR from STMicroelectronics is an off-line quasi-resonant (QR) flyback controller IC with integrated 800 V avalanche-rugged power MOSFET, adjustable current limiting via ZCD pin, hysteretic thermal shutdown at 150–160 °C, and <50 mW standby power at 265 Vac. It delivers up to 20 W in open-frame designs and supports brown-in/brown-out protection for universal AC input (85–265 Vac) applications including LED drivers and auxiliary supplies for TVs and set-top boxes.

For engineers reviewing the VIPER25HDTR datasheet, VIPER25HDTR pinout, VIPER25HDTR application, or VIPER25HDTR equivalent, key selection criteria include its QR valley-switching operation, dual overcurrent protection (static + second-level), programmable overvoltage protection (3.8–4.6 V threshold), and SO-16N package with DRAIN pins thermally connected to metal frame for enhanced heat dissipation.

Technical Context

The VIPER25HDTR implements a current-mode PWM controller with zero-current detection (ZCD) circuitry enabling true quasi-resonant operation-synchronizing MOSFET turn-on to transformer demagnetization valleys. Its internal oscillator provides frequency foldback, limiting max switching to 200–250 kHz (VIPER25H variant), and supports valley-skipping and burst-mode transitions under light load.

Brown-out protection uses a dedicated BR pin with 0.41–0.49 V threshold and 50 mV hysteresis; overvoltage protection is strobed and digitally filtered on the ZCD pin (VOVP = 3.8–4.6 V). The high-voltage start-up circuit draws current directly from the DRAIN pin (VDRAIN_START = 60–100 V) and disables once VDD reaches 13–15 V.

Key Specifications

Pinout & Package

VIPER25HDTR is housed in a SO-16N (Small Outline, 16-pin, narrow) package with exposed DRAIN pins (13–16) thermally connected to the metal frame for efficient heat transfer to PCB copper area. Minimum recommended copper area under DRAIN pins is 100 mm² (35 µm thick) to achieve R_TH-JA = 85 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quasi-resonant flyback controller applications.

Compared with ICE2QS03G and LNK306P, VIPER25HDTR uniquely combines 800 V integration, true QR valley switching, ZCD-programmable current limit, and strobed OVP-making it optimal for 10–20 W universal-input SMPS where EMI, efficiency, and fault robustness are co-prioritized.

Availability

VIPER25HDTR is available at Aetrix Electronics and suitable for LED drivers, auxiliary power supplies for LCD/PDP TVs, adapters for cordless phones, and SMPS for set-top boxes requiring stable component supply, long-term lifecycle support, and compliance with global energy regulations.

Supply support for VIPER25HDTR 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 automotive, industrial, and consumer markets.

VIPER25HDTR belongs to ST's VIPer™ high-voltage AC-DC converter family, engineered specifically for compact, low-cost, energy-efficient offline SMPS targeting consumer electronics, home appliances, and industrial auxiliary supplies.

FAQ

What is the purpose of the ZCD pin in VIPER25HDTR?

The ZCD (Zero-Current Detection) pin serves three critical functions: it senses transformer demagnetization for quasi-resonant valley switching, sets the adjustable drain current limit via RLIM resistor, and hosts the strobed overvoltage protection circuit (VOVP = 3.8–4.6 V). Its internal arming (0.8 V) and triggering (0.6 V) thresholds ensure noise-immune operation during high-dv/dt switching transitions.

How does VIPER25HDTR achieve <50 mW standby power?

VIPER25HDTR achieves sub-50 mW standby power through burst-mode operation (activated when FB voltage falls below 0.6 V), ultra-low quiescent current in shutdown (270 µA at VDD = 7 V), and automatic disabling of the HV start-up circuit once VDD exceeds 13 V. Its internal oscillator halts during burst intervals, minimizing switching and gate drive losses at near-zero load.

Can VIPER25HDTR operate without an auxiliary winding?

No-VIPER25HDTR requires an auxiliary winding to sustain VDD after startup. The internal HV start-up circuit only charges the VDD capacitor initially (−2 to −4 mA from DRAIN); once VDD reaches 13–15 V, the HV generator disables and the IC relies entirely on the auxiliary winding for continuous operation. Without it, VDD collapses below 7.5 V and the device shuts down.

What thermal design considerations apply to the SO-16N package?

The SO-16N package uses pins 13–16 (DRAIN) as thermal pads connected to the internal MOSFET die. To achieve R_TH-JA = 85 °C/W, a minimum 100 mm² copper pour (35 µm thick) must be placed beneath these pins. Thermal vias to inner/ground planes are recommended. Without adequate copper area, junction temperature can exceed 150 °C even at 12 W output, triggering thermal shutdown.