STMicroelectronics VIPER28LE

Overview

VIPER28LE from STMicroelectronics is an off-line high-voltage AC-DC converter IC integrating an 800 V avalanche-rugged N-channel power MOSFET, current-mode PWM controller, dual over-current protection (OCP), output overvoltage protection (OVP), and on-board soft-start. It delivers up to 12 W in open-frame designs at 50 °C ambient, supports 60 kHz or 115 kHz fixed-frequency operation (H-type variant), and achieves ≤30 mW standby power at 265 Vac for energy-compliant auxiliary supplies.

For engineers reviewing the VIPER28LE datasheet, VIPER28LE pinout, VIPER28LE application, or VIPER28LE equivalent, this device is selected for low/medium-power flyback converters requiring integrated high-voltage startup, burst-mode efficiency at light load, thermal shutdown with 30 °C hysteresis, and EPT-based peak power management - especially where board space and BOM count are constrained.

Technical Context

The VIPER28LE implements a current-mode flyback controller with cycle-by-cycle current limiting set via the CONT pin, and a secondary-level OCP (2nd OCP) that triggers hiccup-mode restart upon sustained overload. Its oscillator features ±4 kHz jitter at 250 Hz for EMI reduction, and internal high-voltage startup draws current directly from the DRAIN pin above 80 V.

Protection architecture includes digitally strobed OVP (2.7–3.3 V threshold, 2.2 µs sampling delay), hysteretic thermal shutdown (150–160 °C trip, 30 °C hysteresis), UVLO (VDDon = 13–15 V, VDDoff = 7.5–8.5 V), and burst-mode activation when FB voltage falls below 0.6 V - enabling <30 mW no-load consumption.

Key Specifications

Pinout & Package

VIPER28LE is housed in a 10-pin SDIP (Small Outline Dual In-line Package) with exposed drain pads for enhanced thermal dissipation. The package supports surface-mount assembly and provides low RthJA of 65 °C/W on standard FR4 with 100 mm² copper pour.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar off-line flyback controller applications.

Compared with ICE3B0565J and LNK306P, VIPER28LE offers superior surge immunity (800 V), precise dual-OCP coordination, and EPT-based peak power extension - making it optimal for applications demanding robustness, regulated burst-mode efficiency, and transient overload handling in compact auxiliary supplies.

Availability

VIPER28LE is available at Aetrix Electronics and suitable for ATX auxiliary power supplies, white goods control boards, and DVD player adapters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for VIPER28LE 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.

VIPER28LE belongs to ST's VIPer™ family of high-voltage offline converters, designed specifically for cost-sensitive, space-constrained AC-DC applications where integration, reliability, and regulatory compliance are critical.

FAQ

What is the maximum continuous output power achievable with VIPER28LE in an open-frame design?

VIPER28LE delivers up to 12 W continuous output power in open-frame configurations at 50 °C ambient temperature with adequate heat sinking, as verified in ST's typical power table (Doc ID 15028 Rev 5, p.4). This assumes SO16N or SDIP10 packages mounted on FR4 with 100 mm² copper pour and proper transformer derating for thermal margin.

How does the EPT (Extra Power Timer) function work, and what external component is required?

The EPT pin connects to an external capacitor that controls the duration of elevated peak current capability - allowing temporary output power boost beyond nominal rating. When EPT voltage drops below 0.6 V, the IC reverts to standard current limit; when above 4 V, it disables the function. A typical 100 nF ceramic capacitor yields ~100 ms peak enable time, scalable per Equation in ST Application Note AN4109.

Can VIPER28LE operate without an optocoupler in the feedback loop?

No - VIPER28LE requires feedback via the FB pin, which sources a precise −200 µA current. While primary-side sensing schemes exist, ST's reference designs (e.g., Figure 17) use optocoupler-based secondary regulation to maintain tight output voltage accuracy across line/load/temperature. Direct primary-sense configurations are not supported by the IC's internal error amplifier topology.

What is the purpose of the CONT pin's dual functionality, and how are the two modes selected?

The CONT pin serves two mutually exclusive roles: (1) adjustable current limit set point (via external RLIM resistor to GND), or (2) OVP monitoring (via resistive divider from auxiliary winding). Mode selection is automatic - OVP activates only during MOSFET OFF time when VCONT exceeds VOVP threshold; current limit adjustment operates continuously during ON time based on RLIM value and sink current.