STMicroelectronics VIPER38LD

Overview

VIPER38LD from STMicroelectronics is a high-voltage PWM current-mode flyback controller IC integrating an 800 V avalanche-rugged power MOSFET, embedded HV startup generator, and dual-level overcurrent protection (IDlim = 1.15 A typ, IDMAX = 1.7 A). It operates at 60 kHz (L-type) or 115 kHz (H-type), delivers up to 30 W peak power at 230 Vac, and achieves 30 mW no-load consumption - enabling compliance with stringent energy-saving standards in auxiliary power supplies.

For engineers reviewing the VIPER38LD datasheet, VIPER38LD pinout, VIPER38LD application, or VIPER38LD equivalent, key selection considerations include its SDIP10 package thermal performance (R_TH-JC = 5 °C/W), adjustable extra power timer (EPT), digital noise-filtered overvoltage protection (VOVP = 3.0 V ±0.3 V), and soft-start timing (t_SS = 8.5 ms typ).

Technical Context

The VIPER38LD implements a current-mode PWM control architecture with integrated oscillator jitter (±4 kHz for L-type, ±8 kHz for H-type) to reduce EMI, and features dual OCP thresholds: cycle-by-cycle limiting (IDlim) set via CONT pin resistor and secondary saturation/short-circuit protection (IDMAX = 1.7 A). Its HV startup circuit draws current directly from the DRAIN pin above V_{DRAIN_START} = 80 V, eliminating external startup components.

Operation includes burst mode below V_FBbm = 0.6 V (typ), automatic restart after fault clearance, thermal shutdown at T_SD = 155 °C (hysteresis = 30 °C), and digitally filtered output overvoltage protection strobed at t_STROBE = 2 μs. The internal SenseFET enables lossless current sensing without external shunt resistors.

Key Specifications

Pinout & Package

Available in SDIP10 package (10-pin stretched dual-in-line plastic) with exposed metal pad for thermal dissipation; DRAIN pins (9–12) are internally connected to the metal frame to enhance heat transfer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE3B0565J and LNK364PG, VIPER38LD offers superior surge resilience (800 V), deterministic overload management (EPT), and lower EMI through oscillator jitter - making it optimal for compact, high-reliability auxiliary supplies in energy infrastructure and connected appliances.

Availability

VIPER38LD is available at Aetrix Electronics and suitable for energy meter auxiliary supplies, smart home adapters, and industrial data concentrator power systems requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for VIPER38LD 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 with broad automotive, industrial, and consumer portfolios.

VIPER38LD belongs to the VIPerPlus family of high-voltage offline controllers designed specifically for compact, low-component-count flyback converters targeting energy-efficient auxiliary power supplies in metering, home automation, and white goods.

FAQ

What is the maximum continuous output power achievable with VIPER38LD in an open-frame design?

The VIPER38LD delivers up to 15 W continuous power in an open-frame configuration at 50 °C ambient with adequate heatsinking, as verified in ST's DS10100 Rev 3 datasheet Table 1. Peak power reaches 25 W for ≤2 seconds using the EPT function with appropriate external capacitor sizing.

How does the CONT pin configure dual functionality for current limit and overvoltage monitoring?

When a resistor connects CONT to GND, it scales down the internal IDlim threshold proportionally (per Figure 13). When driven above V_{CONT_h} = 5.5 V, the pin enables strobed OVP monitoring - detecting FB voltage exceeding VOVP (3.0 V) with digital noise filtering and 2 μs strobe window to reject transients.

Can VIPER38LD operate without an optocoupler in the feedback loop?

Yes - VIPER38LD supports primary-side regulation using auxiliary winding sensing. The FB pin accepts voltage derived from an auxiliary winding via resistor divider; burst-mode entry at V_FBbm = 0.6 V and OLP at 3.5 V enable stable regulation without optocoupler or TL431, reducing cost and improving reliability.

What thermal derating applies when using the SDIP10 package on a standard FR4 board?

On a single-sided FR4 board with minimal copper, R_TH-JA = 105 °C/W (Table 4). At 25 °C ambient, maximum continuous power is limited to ~0.9 W before reaching T_J = 150 °C. With 100 mm² copper pour, R_TH-JA improves to 90 °C/W, enabling ~1.2 W continuous - confirming need for proper heatsinking in >10 W designs.