STMicroelectronics VIPER35HDTR

Overview

VIPER35HDTR from STMicroelectronics is a quasi-resonant high-voltage offline converter IC integrating an 800 V avalanche-rugged power MOSFET, current-mode PWM controller, embedded HV start-up, soft-start, and multifunction ZCD pin. It delivers up to 22 W in open-frame designs at 50 °C ambient, supports isolated flyback topology with optocoupler feedback, and achieves <30 mW no-load consumption at 230 VAC.

For engineers reviewing the VIPER35HDTR datasheet, VIPER35HDTR pinout, VIPER35HDTR application, or VIPER35HDTR equivalent, key selection criteria include its 800 V drain rating, quasi-resonant valley-switching operation, brown-out hysteresis (40–60 mV), thermal shutdown at 150–160 °C, and dual-frequency variants (136 kHz L-type / 225 kHz H-type) for EMI or transformer size optimization.

Technical Context

The VIPER35HDTR implements a current-mode quasi-resonant controller synchronized to transformer demagnetization via its ZCD pin, enabling valley-switching to minimize turn-on losses and EMI. Its integrated 800 V MOSFET features R_DS(on) = 4.5 Ω (25 °C) and 9 Ω (125 °C), with senseFET-based current limiting adjustable via external resistor on ZCD.

Brown-out protection uses a resistor divider on BR pin to set independent turn-on/turn-off thresholds (V_BRth = 0.45 V typ., hysteresis = 50 mV), while burst-mode operation below 0.6 V on FB enables <30 mW no-load standby power. Thermal shutdown is hysteric (T_SD = 155 °C typ., ΔT = 30 °C), and fault recovery is auto-restart with controlled VDD recharge via IDDch2 = 0.6 mA.

Key Specifications

Pinout & Package

Package: SO-16 narrow (SO 16 N), thermally enhanced with pins 13–16 connected to internal drain metal frame for improved heat dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quasi-resonant offline converter applications.

Compared with ICE3B0565J and LNK3206D, VIPER35HDTR uniquely combines 800 V ruggedness, true quasi-resonant valley switching, and four-function ZCD integration-enabling higher power density, lower EMI, and fewer external components in regulated flyback designs up to 22 W.

Availability

VIPER35HDTR is available at Aetrix Electronics and suitable for smartphone chargers, set-top box auxiliary supplies, industrial metering systems, and personal care appliance adapters requiring stable component supply, long-term lifecycle support, and compliance with global energy efficiency standards.

Supply support for VIPER35HDTR 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

VIPER™ is ST's proprietary family of high-voltage offline converters targeting cost-sensitive, space-constrained AC-DC power supplies-designed to integrate power switch, controller, and protection in single SO-16 packages for rapid, reliable design-in.

FAQ

What is the difference between VIPER35HDTR and VIPER35LDTR?

The 'H' and 'L' suffixes denote the internal oscillator frequency limit: VIPER35HDTR is rated for 225 kHz maximum switching frequency (typ.), optimized for extended quasi-resonant operation and smaller transformers, while VIPER35LDTR is limited to 136 kHz (typ.), prioritizing lower EMI and simplified filtering. Both share identical pinout, protection features, and 800 V drain rating.

Can VIPER35HDTR operate without an auxiliary winding?

Yes-its embedded HV start-up circuit draws initial charging current directly from the DRAIN pin, enabling operation without an auxiliary winding during startup. However, an auxiliary winding is required for sustained operation to maintain VDD above 8.5 V once the internal start-up current disables after turn-on.

How is overvoltage protection implemented on the ZCD pin?

OVP is configured using a resistor divider from the output to the ZCD pin. When output voltage exceeds the threshold (3.8–4.6 V), the ZCD pin voltage crosses its internal comparator threshold, triggering auto-restart protection. The same ZCD pin simultaneously handles zero-current detection and current-limit setup-no additional components needed.

What thermal derating applies to VIPER35HDTR in SO-16 package?

With standard FR4 PCB (100 mm² copper area), R_thJA = 80 °C/W. At 50 °C ambient, maximum continuous power is ~16 W (open frame) before junction temperature reaches 150 °C. Derating is linear: every 10 °C ambient rise reduces usable power by ~2 W. Pins 13–16 must be soldered to large copper pour for optimal heat transfer.