STMicroelectronics VIPER35HE

Overview

VIPER35HE from STMicroelectronics is a quasi-resonant high-voltage offline converter IC integrating an 800 V avalanche-rugged power MOSFET, embedded HV start-up circuit, and current-mode PWM controller with ZCD-based valley switching. 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 VIPER35HE datasheet, VIPER35HE pinout, VIPER35HE application, or VIPER35HE equivalent, this device is selected for auxiliary power supplies requiring ultra-wide AC input (85–265 VAC), low standby power compliance (Energy Star), and integrated protection including brown-out hysteresis, short-circuit auto-restart, and thermal shutdown with 30 °C hysteresis.

Technical Context

The VIPER35HE implements a quasi-resonant current-mode control architecture where MOSFET turn-on is synchronized to transformer demagnetization via zero-current detection on the ZCD pin, enabling valley switching to minimize EMI and conduction losses. Its dual-threshold ZCD circuit (VZCDAth = 0.8 V, VZCDTth = 0.6 V) ensures reliable arming and triggering while tBLANK = 2.5–6.3 µs suppresses noise-induced false triggers from leakage inductance ringing.

It features a programmable drain current limit (IDlim = 0.65–1.05 A) set via external resistor on ZCD, frequency clamping at 136 kHz (L-type) or 225 kHz (H-type), and burst-mode operation below VFBbm = 0.6 V to achieve <30 mW no-load power. Brown-out protection uses a dedicated BR pin with VBRth = 0.45 V and hysteresis of 50 mV for independent turn-on/turn-off thresholds.

Key Specifications

Pinout & Package

Package: SO-16 Narrow (SO16N), surface-mount, with pins 13–16 internally connected to the metal frame for enhanced thermal dissipation (RthJA = 80 °C/W on FR4 with 100 mm² copper).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE3B0565J and LNK364PG, VIPER35HE provides superior efficiency via valley switching, tighter protection configurability (ZCD/OVP/BR), and regulatory-compliant standby power-making it optimal for compact, high-reliability auxiliary supplies where EMI and thermal performance are critical.

Availability

VIPER35HE is available at Aetrix Electronics and suitable for smartphone chargers, set-top box auxiliary supplies, industrial metering systems, and home appliance control boards requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for VIPER35HE 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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The VIPER™ family targets highly integrated, high-voltage AC-DC conversion-specifically engineered to replace discrete controller+FET combinations in cost- and space-constrained auxiliary power applications.

FAQ

What is the difference between VIPER35HE and VIPER35HS?

VIPER35HE is the 'L-type' variant with a 136 kHz internal frequency clamp (FOSClim), optimized for EMI filter minimization and lower switching losses at medium loads. VIPER35HS is the 'H-type' with 225 kHz clamp, enabling extended quasi-resonant operation range and smaller transformer size-but with higher gate drive losses. Both share identical pinout, protection features, and SO-16N package.

Can VIPER35HE operate without an optocoupler in flyback designs?

No-VIPER35HE requires optocoupler feedback for primary-side regulation. Its FB pin sources current (−215 µA typ.) into the optocoupler LED to close the voltage loop; there is no built-in secondary-side sensing or auxiliary winding regulation capability. Designs omitting optocouplers must use alternative controllers like VIPer0P or LNK320x series.

How is the drain current limit (IDlim) configured on the ZCD pin?

IDlim is set by an external resistor (RLIM) between ZCD and GND. With IZCD = −10 µA, IDlim = 1.0 A; increasing IZCD magnitude (e.g., −105 µA) reduces IDlim to 0.65 A. The relationship is linear and specified in Table 5 of DS10628 Rev 5, enabling precise output power scaling without changing transformer turns ratio.

What thermal derating applies when using VIPER35HE on a standard FR4 PCB?

With 100 mm² of 35 µm copper on a single-layer FR4 board, RthJA = 80 °C/W. At 50 °C ambient, maximum continuous power is limited to ~16 W (per DS10628 Table 1). To sustain 22 W, add thermal vias under pins 13–16 and increase copper area to ≥200 mm², or mount on aluminum-backed PCB to reduce junction temperature rise below 110 °C.