Analog Devices Inc. LT1072CK

Overview

LT1072CK from Analog Devices (formerly Linear Technology) is a monolithic 1.25A current-mode switching regulator in TO-3 metal-can package, supporting buck, boost, flyback, forward, inverting, and Cuk topologies. It operates from 3V to 40V input, delivers up to 20W output power, features internal 65V switch, 40kHz fixed-frequency oscillator, and 6mA quiescent current - ideal for offline converters, battery upconverters, and isolated dual-rail supplies.

For engineers reviewing the LT1072CK datasheet, LT1072CK pinout, LT1072CK application, or LT1072CK equivalent, key selection considerations include its 1.25A switch current limit, flyback-regulated floating outputs without optocouplers, adaptive anti-saturation drive, shutdown mode drawing only 50µA, and compatibility with wide-input industrial and automotive power rails.

Technical Context

The LT1072CK implements current-mode control: switch duty cycle is directly set by sensed switch current rather than output voltage feedback, enabling fast line transient response and simplified loop compensation. Its internal 2.3V low-dropout regulator powers all circuitry, allowing stable operation across the full 3V–40V input range.

It integrates oscillator, error amplifier (gm = 3000–6000 µmho), current-limit comparator, adaptive anti-saturation driver, and 1.25A/65V NPN switch. The VC pin serves quadruple function - compensation node, current limit adjustment, soft-start control, and shutdown trigger - while FB pin supports both standard regulation and flyback mode via external resistor pull-down.

Key Specifications

Pinout & Package

K Package: 4-lead TO-3 metal can (case grounded), θJC = 8°C/W, θJA = 35°C/W, TJMAX = 150°C. Designed for high-power dissipation without heatsink in moderate ambient conditions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1072CT and LT1072CN8, the LT1072CK offers lowest thermal resistance (35°C/W), direct case-to-ground path for EMI shielding, and highest reliability in high-temperature environments - making it optimal for sealed industrial enclosures and high-reliability offline power supplies.

Availability

LT1072CK is available at Aetrix Electronics and suitable for offline AC/DC converters, battery-powered upconverters, and isolated dual-rail supplies requiring stable component supply, long-lifecycle assurance, and traceable sourcing.

Supply support for LT1072CK 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, inheriting its legacy of high-performance analog and power management ICs designed for precision, reliability, and rugged operation.

The LT1072 product line was engineered as a monolithic high-current switching regulator family targeting medium-power industrial, telecom, and instrumentation applications where simplicity, topology flexibility, and robustness outweigh cost-driven integration trade-offs.

FAQ

What is the maximum input voltage rating for the LT1072CK?

The LT1072CK has an absolute maximum input voltage of 40V, as specified for the standard LT1072 variant (not HV). Exceeding this may cause switch breakdown. For 60V input applications, the LT1072HVCK variant must be used instead. The LT1072CK's 65V switch breakdown voltage provides necessary margin but does not extend the rated operating range beyond 40V.

Can the LT1072CK generate isolated outputs without an optocoupler?

Yes - the LT1072CK supports flyback-regulated mode where the FB pin is pulled low, enabling regulation of the reflected flyback pulse amplitude. This allows fully floating, isolated outputs up to the transformer's breakdown voltage without optocouplers or secondary-side references. The LT1072CK includes internal blanking to ignore leakage spikes, improving regulation accuracy.

How does the VC pin function in the LT1072CK?

The VC pin in the LT1072CK serves four critical roles: (1) compensation node for loop stability, (2) current limit adjustment via external clamp, (3) soft-start control using capacitor coupling, and (4) shutdown activation when pulled below 0.15V. At normal operation, VC sits between 0.9V and 2.0V - its voltage directly sets peak switch current.

What is the thermal performance difference between LT1072CK and LT1072CT?

The LT1072CK (TO-3) has θJA = 35°C/W and θJC = 8°C/W, while the LT1072CT (TO-220) has θJA = 50°C/W and θJC = 8°C/W. The LT1072CK's metal-can construction provides superior heat conduction to chassis or heatsink, enabling higher continuous power in confined spaces. Its case is internally tied to GND, simplifying grounding and EMI mitigation.

Does the LT1072CK support external frequency synchronization?

Yes - the LT1072CK can be synchronized to an external clock in the 48kHz–70kHz range by pulling the VC pin to ground with a narrow (<1µs) pulse via an external transistor. This feature reduces EMI by aligning switching edges across multiple regulators. Synchronization does not affect regulation accuracy, though very low compensation resistors may increase offset voltage slightly.