STMicroelectronics VIPER28LDTR

Overview

VIPER28LDTR from STMicroelectronics is a high-voltage AC-DC converter IC integrating an 800 V avalanche-rugged power MOSFET, current-mode PWM controller, and embedded HV startup circuit. It delivers up to 12 W continuous output in open-frame designs at 50 °C ambient, supports dual switching frequencies (60 kHz or 115 kHz), and achieves ≤30 mW no-load consumption at 230 Vac - enabling compliance with stringent energy-saving standards for auxiliary power supplies.

For engineers reviewing the VIPER28LDTR datasheet, VIPER28LDTR pinout, VIPER28LDTR application, or VIPER28LDTR equivalent, key selection considerations include its adjustable cycle-by-cycle overcurrent threshold (IDlim = 0.8 A typ.), integrated extra power timer (EPT) for 2-second overload tolerance, digital noise-filtered output overvoltage protection (VOVP = 3.0 V ±0.3 V), and SO16 narrow package thermal resistance (RthJA = 105 °C/W on standard FR4).

Technical Context

The VIPER28LDTR implements a current-mode flyback controller with integrated 800 V power switch, eliminating external HV startup components. Its oscillator features jittered frequency modulation (±4 kHz for L-type, ±8 kHz for H-type) to reduce EMI peaks, and burst-mode operation below 0.6 V FB input enables ultra-low standby power.

Protection architecture includes dual-level OCP (IDlim = 0.8 A and IDMAX = 1.2 A), strobed digital OVP with 2.2 µs response, thermal shutdown at 155 °C (30 °C hysteresis), and automatic hiccup-mode restart after fault clearance - all managed without external supervision.

Key Specifications

Pinout & Package

VIPER28LDTR uses the SO16 narrow (SOIC-16) surface-mount package with exposed drain pads (pins 13–16) for enhanced thermal dissipation. The package measures 10.3 × 7.5 mm with 1.27 mm pitch and is supplied in tape-and-reel format.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage flyback controller applications.

Compared with VIPER28LDTR, ICE3B0565J trades 800 V ruggedness and EMI-reducing jitter for lower unit cost, while VIPER06XS retains voltage rating and package compatibility but removes critical configuration options for OCP and overload management - making VIPER28LDTR optimal for universal-input, high-reliability auxiliary supplies requiring adaptive protection.

Availability

VIPER28LDTR is available at Aetrix Electronics and suitable for smart energy meters, AC-DC adapters, and home appliance auxiliary power supplies requiring stable component supply across multi-year production cycles.

Supply support for VIPER28LDTR 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.

VIPER28 belongs to ST's VIPer Plus family of high-voltage converters designed specifically for compact, low-component-count AC-DC flyback power supplies targeting energy-efficient auxiliary and adapter applications.

FAQ

What is the maximum continuous output power achievable with VIPER28LDTR in a vented open-frame design?

VIPER28LDTR delivers up to 12 W continuous output power at 50 °C ambient temperature in an open-frame configuration with adequate heat sinking, as verified in ST's DocID15028 Rev 6 (Table 2). This assumes SO16N mounting on standard FR4 with 100 mm² copper pour, and accounts for thermal derating above 50 °C ambient per RthJA = 105 °C/W.

How does the Extra Power Timer (EPT) function protect the system during overload conditions?

The EPT pin accepts an external capacitor that sets a programmable 2-second overload sustain window. When FB voltage exceeds 3.5 V (VFBlin), the IC enters extra-power mode - maintaining regulation while limiting peak drain current to IDlim. After the capacitor discharges to VEPT(RESTART) ≈ 0.6 V, the IC either resumes normal operation or enters hiccup mode if overload persists beyond the timer window.

Can VIPER28LDTR operate without an optocoupler in the feedback loop?

No - VIPER28LDTR requires a feedback signal on the FB pin for closed-loop regulation. While it supports primary-side sensing topologies using auxiliary winding voltage, ST's reference designs (Figures 15–16) and electrical characteristics specify operation with optocoupler-based secondary-side regulation. The FB pin's 0.6 V burst-mode threshold and 3.5 V overload detection require accurate voltage referencing not achievable without isolation.

What is the purpose of the N.A. pin (pin 4) in the SO16N package, and how should it be handled?

Pin 4 (N.A.) is mechanically bonded to the controller die pad and serves as a thermal and noise-shielding node. ST explicitly recommends connecting it to GND (pins 1–2) to improve noise immunity and enhance thermal conduction from the controller die. Leaving it floating degrades EMI performance and may cause erratic OVP or soft-start behavior under high dv/dt conditions.