STMicroelectronics VIPER37LDTR

Overview

VIPER37LDTR from STMicroelectronics is a fixed-frequency offline AC-DC converter IC integrating an 800 V avalanche-rugged N-channel power MOSFET, current-mode PWM controller, adjustable cycle-by-cycle overcurrent protection (OCP), brownout detection, and burst-mode operation for <30 mW standby power at 265 Vac. It delivers up to 20 W in open-frame designs and supports flyback topologies for auxiliary and low/medium-power SMPS in consumer electronics.

For engineers reviewing the VIPER37LDTR datasheet, VIPER37LDTR pinout, VIPER37LDTR application, or VIPER37LDTR equivalent, key selection considerations include its 60 kHz switching frequency (L-type), integrated high-voltage startup, dual OCP levels (primary + 2nd-level hiccup), thermal shutdown with 30 °C hysteresis, and SO16 narrow package with 16 pins including five DRAIN terminals for enhanced thermal dissipation.

Technical Context

The VIPER37LDTR implements a current-mode PWM control architecture with leading-edge blanking (300 ns), adjustable current limit via the CONT pin, and digitally filtered overvoltage protection strobed at 2.2 µs. Its oscillator includes ±4 kHz frequency jittering at 60 kHz to reduce EMI filter cost and complexity.

Brownout protection uses a dedicated BR pin with 0.45 V threshold (±40 mV) and 50 mV hysteresis, while thermal shutdown activates at 155 °C (typ.) with 30 °C hysteresis. The device enters burst mode when FB voltage falls below 0.6 V, reducing no-load consumption to <30 mW at 265 Vac.

Key Specifications

Pinout & Package

VIPER37LDTR is housed in a SO16 narrow (SOIC-16) surface-mount package with exposed thermal pad and five parallel DRAIN pins (pins 13–16 and pin 1) for low-thermal-resistance heat transfer to PCB copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar offline flyback controller applications.

Compared with ICE3B0565J and LNK364PG, VIPER37LDTR offers superior input voltage range (800 V), direct brownout integration, and user-adjustable current limit - making it optimal for universal-input, thermally constrained, and regulatory-compliant auxiliary SMPS where design simplicity and reliability are critical.

Availability

VIPER37LDTR is available at Aetrix Electronics and suitable for set-top box auxiliary supplies, DVD recorder primary SMPS, and ATX standby power systems requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for VIPER37LDTR 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.

VIPER37LDTR belongs to the VIPerPlus family of high-voltage offline converters engineered specifically for cost-effective, compact, and energy-efficient AC-DC power supplies in consumer and home appliance applications.

FAQ

What is the purpose of the BR pin on VIPER37LDTR?

The BR (Brownout) pin monitors a scaled version of the rectified input voltage. When the voltage at this pin falls below 0.45 V (with 50 mV hysteresis), the IC disables switching to protect downstream circuitry from undervoltage conditions. It can be grounded if brownout protection is not required, simplifying design in stable-line applications.

How does the CONT pin adjust overcurrent protection?

The CONT pin sets the cycle-by-cycle current limit threshold. Connecting an external resistor between CONT and GND lowers the default 1 A limit proportionally - e.g., a 10 kΩ resistor reduces it to ~0.7 A. This allows precise adaptation to transformer turns ratio and output power requirements without changing the MOSFET.

Can VIPER37LDTR operate without an auxiliary winding?

Yes - its high-voltage startup circuit draws charging current directly from the DRAIN pin, enabling operation without an auxiliary winding during initial startup. However, once running, the VDD capacitor must be sized to sustain operation until the auxiliary winding takes over; otherwise, repeated restarts occur due to VDD droop.

What thermal derating applies to VIPER37LDTR in SO16 narrow package?

In a standard single-sided FR4 board with 100 mm² copper pour, the junction-to-ambient thermal resistance is 80 °C/W. At 50 °C ambient, maximum continuous power is limited to ~15 W before exceeding the 150 °C max junction temperature - consistent with the datasheet's "open frame" rating at that temperature.