Infineon Technologies IRS27951SPBF

Overview

IRS27951SPBF from Infineon Technologies (formerly International Rectifier) is a self-oscillating resonant half-bridge controller IC for LLC DC-DC converters, featuring programmable 44–299 kHz switching frequency, 170–250 ns dead time, 600 V high-side floating offset capability, 300 mA HO source / 900 mA LO sink drive strength, and over-current protection via low-side MOSFET R_DS(on). It targets high-efficiency AC-DC adapters and TV power supplies.

For engineers reviewing the IRS27951SPBF datasheet, IRS27951SPBF pinout, IRS27951SPBF application, or IRS27951SPBF equivalent, key selection criteria include its fixed 50% duty cycle, micropower sleep mode (150–200 µA), CT/SD-controlled shutdown, bootstrap operation up to +600 V, and SOIC-8N package compatibility with resonant converter layout constraints.

Technical Context

The IRS27951SPBF implements a voltage-controlled oscillator with external RT/CT timing network, generating complementary HO/LO gate outputs with matched dead time. Its floating high-side driver uses bootstrap charging and dv/dt-tolerant level shifting to sustain VS node operation up to 600 V referenced to COM.

Over-current protection is implemented by sensing voltage across the low-side MOSFET's R_DS(on) at the VS node, triggering fault latching when VOCP exceeds 2.0 V (typ). The CT/SD pin supports both soft-start initiation and user-triggered micropower sleep mode via voltage threshold detection (VEN1 = 1.05 V, VEN2 = 0.85 V).

Key Specifications

Pinout & Package

IRS27951SPBF is housed in an 8-pin SOIC-N (SOIC8N) package with standard 1.27 mm pitch, gull-wing leads, and exposed pad not electrically connected. Thermal resistance R_thJA = 150 °C/W under board-mounted still-air conditions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar resonant half-bridge controller applications.

Compared with IRS27952SPBF, the IRS27951SPBF offers lower standby power but requires external 5 V bias; versus UCC256301D, it integrates gate drivers and simplifies layout at the cost of programmability and adaptive control.

Availability

IRS27951SPBF is available at Aetrix Electronics and suitable for LCD TV power supplies, telecom rectifiers, and PC ATX main converters requiring stable component supply, long-term lifecycle support, and lead-free compliance.

Supply support for IRS27951SPBF 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

Infineon Technologies acquired International Rectifier in 2015 and continues its legacy of high-voltage power ICs for energy-efficient power conversion.

The IRS2795x family was designed specifically for self-oscillating LLC resonant half-bridge topologies in consumer and telecom power supplies, emphasizing minimal external components and robust high-voltage operation.

FAQ

What is the maximum allowable dV/dt on the VS pin?

The IRS27951SPBF specifies ±50 V/ns as the maximum allowable slew rate on the VS node. Exceeding this may cause false triggering of the high-side level shifter or premature over-current detection. Layout best practices include minimizing loop area between VS, HO, and low-side MOSFET source, and using local 100 nF ceramic decoupling at VB and COM.

Can IRS27951SPBF drive GaN HEMTs directly?

Yes - its 300 mA HO source and 900 mA LO sink currents, combined with <65 ns fall time into 4.7 nF load, support direct gate driving of 100–200 mΩ GaN devices. However, external negative turn-off voltage (−2 V to −5 V) via Zener clamp is recommended to ensure robust Miller immunity during high dV/dt switching.

How is over-current protection reset after fault latching?

Over-current protection triggers latched shutdown: the IC stops switching and enters sleep mode until V_CC drops below 8.1 V (UVLO threshold), then reboots. No external reset pin exists. To enable auto-restart, design the V_CC supply with a bleed resistor that discharges C_VCC within 10–20 ms after fault.

Is the CT/SD pin compatible with microcontroller GPIO for active shutdown?

Yes - the CT/SD pin accepts TTL/CMOS logic levels. Driving it below 0.85 V with a GPIO (open-drain or push-pull) initiates micropower sleep mode with <200 µA V_CC draw. Ensure GPIO can sink ≥10 µA startup current and has sufficient noise immunity, as the pin also functions as oscillator timing node during normal operation.