Analog Devices Inc. LT1170CT#PBF

Overview

LT1170CT#PBF from Analog Devices (formerly Linear Technology) is a monolithic 5A, 100kHz current-mode switching regulator IC in a 5-lead plastic TO-220 package. It integrates a high-current power switch, oscillator, error amplifier, shutdown logic, and adaptive anti-saturation driver. Designed for buck, boost, flyback, inverting, and Cuk topologies, it delivers up to 100W output power with 3V–60V input range and 6mA quiescent current - used in industrial DC-DC conversion where high efficiency and topology flexibility are required.

For engineers reviewing the LT1170CT#PBF datasheet, LT1170CT#PBF pinout, LT1170CT#PBF application, or LT1170CT#PBF equivalent, key selection criteria include its internal 5A/75V switch, flyback-regulated floating output capability, 85–97% maximum duty cycle, shutdown mode drawing only 50µA, and compatibility with standard 5-pin TO-220 thermal management.

Technical Context

The LT1170CT#PBF implements current-mode control: the internal oscillator initiates each switching cycle, and the power switch turns off when sensed current reaches a level set by the VC pin voltage. This architecture provides inherent cycle-by-cycle current limiting, fast line transient response, and simplified loop compensation across wide input/output ranges.

It supports dual regulation modes: normal mode (FB referenced to 1.24V internal bandgap) and flyback mode (FB pulled low to enable 15V ±1.3V isolated reference). The VC pin serves four functions - error amplifier output, soft-start node, current limit adjust, and shutdown control - with clamp voltages at 0.25V (low) and 2.3V (high).

Key Specifications

Pinout & Package

The LT1170CT#PBF uses a 5-lead plastic TO-220 package (T package), with the metal tab internally connected to GND for thermal and electrical grounding. Pin 1 = VIN, Pin 2 = VSW, Pin 3 = GND (tab), Pin 4 = FB, Pin 5 = VC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3775EFE#TRPBF and LM5088MHX/NOPB, the LT1170CT#PBF uniquely combines 5A integration, flyback regulation, 100kHz operation, and TO-220 thermal performance - making it optimal for cost-sensitive, isolated, or wide-input industrial DC-DC where simplicity and proven reliability outweigh ultra-high frequency or digital control needs.

Availability

LT1170CT#PBF is available at Aetrix Electronics and suitable for industrial automation, battery-powered instrumentation, isolated sensor interfaces, and telecom power conversion requiring stable component supply over extended production lifecycles.

Supply support for LT1170CT#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, datasheets, and application notes for legacy Linear parts including the LT1170 series.

The LT1170CT#PBF belongs to Linear's monolithic high-power switching regulator family, designed specifically for rugged, topology-flexible DC-DC conversion in industrial, automotive, and telecom environments where integration, thermal robustness, and wide input range are critical.

FAQ

What is the maximum continuous output power achievable with the LT1170CT#PBF in buck configuration?

The LT1170CT#PBF supports up to 100W continuous output power in buck mode under appropriate thermal conditions. This is calculated as P_OUT ≈ 5A × V_OUT, assuming efficient layout, adequate heatsinking on the TO-220 tab, and input voltage within 3V–60V. At 12V output, this enables 5A delivery; derating applies above 85°C ambient or with poor copper pour.

Does the LT1170CT#PBF support flyback topology with true galvanic isolation?

Yes, the LT1170CT#PBF supports fully isolated flyback operation. When the FB pin is pulled below 0.5V via an external resistor, it activates flyback mode with a 15.0V ±1.3V reference, allowing regulation of secondary-side voltage without direct feedback connection. Output isolation is limited only by transformer winding breakdown voltage - confirmed in the LT1170/LT1171/LT1172 datasheet Figure TA03.

What thermal resistance does the LT1170CT#PBF exhibit in its TO-220 package?

The LT1170CT#PBF has θ_JA = 75°C/W and θ_JC = 2°C/W in the 5-lead plastic TO-220 (T) package. This means junction-to-case thermal resistance is extremely low (2°C/W), enabling effective heat transfer to an external heatsink, while junction-to-ambient depends on PCB copper area - verified in the "Order Information" table on page 3 of the LT1170 datasheet.

Can the LT1170CT#PBF be synchronized to an external clock?

Yes, the LT1170CT#PBF supports external synchronization between 120kHz and 160kHz. Synchronization is achieved by pulling the VC pin to ground with a narrow (<0.3µs) pulse from an external transistor, as detailed in Application Note AN19 and Figures OP01/OP02 in the LT1170 datasheet. This avoids EMI peaks and enables timing alignment in multi-regulator systems.

How does the LT1170CT#PBF implement current limiting and overload protection?

The LT1170CT#PBF uses true current-mode control: switch conduction ends when sensed current reaches a threshold set by the VC pin voltage (0–2V → 0–5A). This provides per-cycle limiting, preventing destructive currents during short circuits. Combined with thermal foldback behavior and 50µA shutdown mode, it delivers robust self-protection without external circuitry - validated in the "Operation" section (page 9) and Electrical Characteristics table (page 4).