Analog Devices Inc. LT1370IR#PBF

Overview

LT1370IR#PBF from Analog Devices (formerly Linear Technology) is a monolithic 500kHz current-mode switching regulator IC with integrated 6A power switch, supporting boost, buck, flyback, forward, inverting, and Cuk topologies. It delivers up to 2A output at 12V from 5V input with 92% peak efficiency, operates down to 2.7V input, and regulates both positive and negative outputs using separate FB and NFB pins.

For engineers reviewing the LT1370IR#PBF datasheet, LT1370IR#PBF pinout, LT1370IR#PBF application, or LT1370IR#PBF equivalent, key selection criteria include its 6A internal switch, 0.065Ω typical R_DS(on), ±1.245V/–2.48V dual reference architecture, 12µA shutdown current, and compatibility with surface-mount inductors as small as 4.7µH for high-frequency operation.

Technical Context

The LT1370IR#PBF implements current-mode control with adaptive anti-saturation driver circuitry, enabling precise pulse-by-pulse current limiting and fast transient response to input voltage changes. Its error amplifier features nonlinear transconductance (1100–1900 µmho) that increases 10× when FB exceeds V_REF by 40mV, reducing startup/overload overshoot.

Oscillator frequency shifts 5:1 under overload (FB < 0.6V), protecting external components; synchronization is supported from 600kHz to 800kHz via the S/S pin. The VC pin serves triple function-compensation node, soft-start control, and current limit adjustment-with clamping thresholds at 0.2–0.52V (low) and 1.5–2.3V (high).

Key Specifications

Pinout & Package

LT1370IR#PBF uses a 7-lead TO-220 (T7) package with exposed tab connected to GND for thermal dissipation. θ_JA = 50°C/W, θ_JC = 4°C/W. Mounting requires soldering the tab to a large copper area or heatsink.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switching regulator applications.

Compared with LTC3780EFE#PBF and TPS55340RTER, the LT1370IR#PBF uniquely integrates a 6A switch with dual-reference regulation in a TO-220 package, delivering the simplest BOM and smallest footprint for bipolar-output DC/DC conversion below 2 A.

Availability

LT1370IR#PBF is available at Aetrix Electronics and suitable for laptop power supplies, industrial flyback converters, battery-powered inverters, and laser biasing circuits requiring stable component supply and long-term obsolescence management.

Supply support for LT1370IR#PBF 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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LT1370 series.

The LT1370IR#PBF belongs to Linear's high-efficiency monolithic switching regulator family, designed specifically for compact, multi-topology DC/DC conversion in portable and industrial equipment where dual-polarity outputs and minimal external components are critical.

FAQ

What is the maximum continuous output current achievable with the LT1370IR#PBF in a boost configuration?

The LT1370IR#PBF supports up to 2 A continuous output current at 12 V from a 5 V input, as verified in the TA01 typical application circuit. This assumes proper thermal management using the TO-220 tab mounted to ≥1 in² copper area, ambient temperature ≤50°C, and 10 µH inductor. Peak switch current remains within the 6 A limit, and efficiency stays above 90% across the load range. Derating is required above 60°C ambient.

Can the LT1370IR#PBF regulate both positive and negative outputs simultaneously in one circuit?

Yes, the LT1370IR#PBF can regulate both polarities simultaneously using the TA04 dual-output flyback application. The FB pin senses the positive output against +1.245 V reference, while the NFB pin senses the negative output against –2.48 V reference. When both pins are active, the IC prevents either rail from exceeding its setpoint, providing inherent cross-regulation without optocouplers or secondary controllers.

What is the purpose of the VC pin on the LT1370IR#PBF, and how is it used in practice?

The VC pin on the LT1370IR#PBF is the error amplifier output and serves three functions: frequency compensation (via RC network to ground), soft-start control (via capacitor-coupled clamp), and current limit adjustment (via external voltage clamp). During operation, VC voltage ranges from ~1.0 V (light load) to ~1.9 V (full load). Clamping VC below 0.9 V forces zero duty cycle, enabling idle mode or precise current limiting.

Does the LT1370IR#PBF require an external synchronization signal to operate, or is it self-oscillating?

The LT1370IR#PBF is fully self-oscillating at 500 kHz nominal and does not require external synchronization. The S/S pin is optional: leaving it floating, tying it to VIN, or pulling it high enables normal operation. Only when system-level noise reduction or timing alignment is needed should a 600–800 kHz logic-level clock be applied to the S/S pin-this overrides the internal oscillator without affecting regulation stability.

How does the LT1370IR#PBF protect itself and external components during overload or short-circuit conditions?

The LT1370IR#PBF employs three coordinated protections: (1) pulse-by-pulse current limiting caps switch current at 6 A; (2) oscillator frequency shifting reduces switching frequency 5:1 when FB drops below 0.6 V, lowering peak energy per cycle; and (3) thermal shutdown activates if junction temperature exceeds 125°C. These mechanisms prevent destructive power dissipation in the internal switch and external inductor/diode during sustained faults.