STMicroelectronics L6598D

Overview

L6598D from STMicroelectronics is a high-voltage resonant controller IC designed for half-bridge LLC and series-resonant AC/DC power supplies, featuring 600 V high-side rail capability, ±50 V/ns dV/dt immunity across –40 °C to +125 °C, 250 mA source / 450 mA sink driver current, and integrated bootstrap diode - enabling compact, robust adapter designs up to 400 kHz switching frequency.

For engineers reviewing the L6598D datasheet, L6598D pinout, L6598D application, or L6598D equivalent, key selection criteria include soft-start frequency shifting (120 kHz → 60 kHz), high-accuracy current-controlled oscillator (±3% fmin tolerance), sense op amp with 1 MHz GBW and ±10 mV offset, and dual enable inputs (latched EN1 @ 0.6 V, unlatched EN2 @ 1.2 V) for system-level fault recovery and sequencing control.

Technical Context

The L6598D implements a dedicated timing architecture where soft-start is governed by CSS ramp charging into a transconductance amplifier, subtracting from Ifstart to linearly shift oscillator frequency from fstart to fmin - eliminating fixed-threshold timing dependencies. Its oscillator uses mirrored current sources (x4/x8) driving Cf to generate precise triangular waveforms, with fmin = 1.41/(Rfmin·Cf) valid from 30–100 kHz.

High/low-side drivers incorporate internal logic-enforced deadtime (270 ns typ.) to prevent cross-conduction, while the patented integrated bootstrap DMOS (150 Ω RDSon) replaces external diodes and is synchronized with LVG output - reducing component count without sacrificing recharging efficiency at frequencies up to 200 kHz.

Key Specifications

Pinout & Package

Available in SO16N (small-outline 16-pin) package with 1.27 mm pitch, 10 mm × 4 mm body, and ECOPACK® RoHS-compliant finish. Thermal resistance RthJA = 120 °C/W enables operation up to +125 °C ambient without forced cooling in typical 65–150 W adapters.

Key Features

Applications

Equivalent & Alternatives

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

Compared with FAN7688 and UCC256301, the L6598D offers analog simplicity, integrated bootstrap, and proven stability in cost-sensitive 65–150 W adapters - making it optimal where minimal external components, deterministic analog behavior, and rapid time-to-market outweigh programmability or ultra-high-frequency needs.

Availability

L6598D is available at Aetrix Electronics and suitable for USB-C PD adapters, industrial AC/DC modules, LED driver power supplies, and server auxiliary rails requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L6598D 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, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The L6598D belongs to ST's high-voltage resonant controller product line, engineered specifically for compact, efficient half-bridge LLC converters in AC/DC adapters - emphasizing integration, ruggedness, and ease of use in cost-sensitive power applications.

FAQ

What is the purpose of the CSS pin and how does it affect startup behavior?

The CSS pin connects to an external capacitor that sets the soft-start duration via linear voltage ramp generation. As CSS charges, the oscillator frequency shifts from fstart (e.g., 120 kHz) to fmin (e.g., 60 kHz) over time TSS = 0.15 s/µF × CSS. This controlled ramp prevents inrush current and ensures zero-voltage switching (ZVS) is established before full-load operation begins.

Can the L6598D drive both MOSFETs and IGBTs in half-bridge configuration?

Yes - the L6598D's 450 mA sink / 250 mA source drivers and 600 V high-side rating support both power MOSFETs and IGBTs. Its 270 ns minimum deadtime prevents shoot-through, and the integrated bootstrap DMOS handles the floating supply requirements for either device type without external diodes.

How does the sense op amp interface with the oscillator for current-mode control?

The sense op amp output (OPout) connects directly to the Rfmin pin. When current-sense voltage exceeds threshold, OPout sinks current into Rfmin, increasing the oscillator's effective current and raising switching frequency - thereby reducing resonant tank gain to regulate output current. This enables fast, analog closed-loop protection without digital intervention.

What is the functional difference between EN1 and EN2 pins?

EN1 is a latched enable: a >0.6 V pulse forces immediate shutdown (LVG/HVG low, oscillator halted) until full power cycle. EN2 is unlatched: a >1.2 V pulse resets EN1 latch and initiates new soft-start sequence. This allows independent fault detection (e.g., overtemperature on EN1) and remote recovery (e.g., microcontroller reset on EN2).