Analog Devices Inc. LT1244IS8#TRPBF

Overview

LT1244IS8#TRPBF from Analog Devices is an 8-pin, fixed-frequency, current-mode PWM controller optimized for off-line and DC/DC converters. It delivers 1A totem-pole output drive, operates up to 500kHz switching frequency, features 50ns current sense delay and active undervoltage lockout with 16V start-up threshold - enabling robust gate driving of power MOSFETs in isolated flyback and forward converters.

For engineers reviewing the LT1244IS8#TRPBF datasheet, LT1244IS8#TRPBF pinout, LT1244IS8#TRPBF application, or LT1244IS8#TRPBF equivalent, key selection criteria include its 50ns current sense delay, 16V UVLO start-up threshold, 1A peak output sink/source capability, trimmed oscillator sink current (8.2mA), and -40°C to 125°C industrial temperature range.

Technical Context

The LT1244IS8#TRPBF implements a fixed-frequency current-mode control architecture with leading-edge blanking on the ISENSE comparator and a tightly trimmed 8.2mA oscillator discharge current. Its error amplifier provides 90dB DC gain and 1MHz unity-gain bandwidth, with internal 2.5V reference tied to the FB pin.

Oscillator timing is set via external RT/CT network; output switching frequency equals half the oscillator frequency (e.g., 1MHz oscillator → 500kHz output). The device actively pulls both OUTPUT and VREF low during undervoltage lockout using Darlington PNP transistors, eliminating need for external pull-down resistors.

Key Specifications

Pinout & Package

S8 package: 8-lead plastic SOIC, –40°C to 125°C operating temperature range, JEDEC MS-012AC compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar current-mode PWM controller applications.

Compared with UC3844N and UCC2802DR, the LT1244IS8#TRPBF offers superior high-frequency stability via 50ns current sense delay and built-in blanking, tighter oscillator tolerance via trimmed 8.2mA sink current, and enhanced system safety through active dual-rail pull-down during UVLO - making it optimal for demanding industrial and telecom power designs.

Availability

LT1244IS8#TRPBF is available at Aetrix Electronics and suitable for off-line converters, DC/DC regulators, and industrial power supplies requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT1244IS8#TRPBF 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

Analog Devices (now part of Analog Devices, Inc. following merger with Linear Technology) is a global leader in high-performance analog, mixed-signal, and power management ICs.

The LT1241 series - including LT1244IS8#TRPBF - was designed specifically for high-reliability, high-frequency current-mode switching power supplies targeting industrial, telecom, and medical equipment where precision timing, noise immunity, and thermal robustness are critical.

FAQ

What is the UVLO start-up threshold voltage for LT1244IS8#TRPBF?

The LT1244IS8#TRPBF has a guaranteed UVLO start-up threshold of 15V to 17V, with typical value 16V. This allows reliable activation after rectified AC line voltage reaches sufficient level in off-line applications. The hysteresis is 5.5V, ensuring clean turn-off below ~10.5V. This specification is validated across the full –40°C to 125°C operating range per the official datasheet.

Does LT1244IS8#TRPBF support 500kHz switching operation?

Yes, the LT1244IS8#TRPBF supports up to 500kHz output switching frequency - achieved by running its internal oscillator at 1MHz and dividing by two. This capability is enabled by its 50ns current sense delay, eliminated cross-conduction in the output stage, and trimmed 8.2mA oscillator sink current, all confirmed in the LT1241 Series datasheet Rev B.

How does the leading-edge blanking function on LT1244IS8#TRPBF?

The LT1244IS8#TRPBF incorporates fixed-duration leading-edge blanking of 100ns on the ISENSE comparator output, triggered at each OUTPUT turn-on edge. This suppresses false triggering from transformer leakage spikes and diode reverse recovery noise. Blanking time scales down linearly as FB pin voltage drops below 2.5V - minimizing blanking during short-circuit faults.

What is the purpose of the active pull-down on VREF and OUTPUT pins during UVLO?

During undervoltage lockout, the LT1244IS8#TRPBF actively pulls both VREF and OUTPUT low via internal Darlington PNP transistors. This holds the external MOSFET gate off without needing an external pull-down resistor, and allows the VREF pull-down to reset an external soft-start capacitor - enabling controlled, repeatable startup sequencing in complex power systems.

Can LT1244IS8#TRPBF drive large-gate-charge MOSFETs directly?

Yes, the LT1244IS8#TRPBF features a ±1A totem-pole output stage with 40ns rise and 30ns fall times into 1nF, enabling direct drive of high-Ciss MOSFETs such as 600V/2A superjunction devices. Its 18V output clamp prevents gate oxide overstress, and elimination of cross-conduction current ensures clean switching transitions without shoot-through risk.