Analog Devices Inc. LT1268CT#PBF

Overview

LT1268CT#PBF from Analog Devices (formerly Linear Technology) is a monolithic 7.5A, 150kHz current-mode switching regulator IC in a 5-lead TO-220 package. It integrates a high-current switch, oscillator, error amplifier, and protection circuitry, enabling buck, boost, flyback, and inverting topologies. Key confirmed specs: 3.5V–30V input range, 7mA quiescent current, 1.244V reference voltage, 0.18Ω typical switch R_DS(on), and 65% max duty cycle - used in high-efficiency boost converters delivering 5.3V ±1% at 3.75A.

For engineers reviewing the LT1268CT#PBF datasheet, LT1268CT#PBF pinout, LT1268CT#PBF application, or LT1268CT#PBF equivalent, this page delivers verified functional identity, thermal and electrical limits, package-specific derating guidance, real-world efficiency curves, and validated alternative options for industrial power supply design.

Technical Context

The LT1268CT#PBF implements current-mode control with adaptive anti-saturation switch drive to maintain efficiency across wide load ranges. Its internal 7.5A switch features 60V breakdown rating and 0.18Ω on-resistance at ≤100°C, supporting continuous operation up to 125°C junction temperature with θ_JA = 50°C/W.

It includes a 1.244V ±9mV reference with 0.03%/V line regulation, 3000–6000 µmho error amplifier transconductance, and externally synchronizable 120–180kHz switching frequency. Shutdown mode reduces supply current to 100µA typical, triggered by <250mV on the VC pin.

Key Specifications

Pinout & Package

LT1268CT#PBF uses a 5-lead TO-220 (T package) with case-connected VIN pin for direct heatsink mounting. Thermal resistance is θ_JC = 2°C/W; layout must isolate FB and VC traces from noise sources.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3780EFE#PBF and LM5118MH/NOPB, the LT1268CT#PBF offers lowest component count and fastest time-to-operational prototype for ≤30V, ≤7.5A boost/buck applications - trading programmability and ultra-wide VIN for out-of-box reliability and thermal simplicity in TO-220 form factor.

Availability

LT1268CT#PBF is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered upconverters, and embedded PC auxiliary rails requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production lots.

Supply support for LT1268CT#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, inheriting its precision analog and power management portfolio. Linear pioneered monolithic high-current switching regulators with integrated power stages.

The LT1268CT#PBF belongs to Linear's legacy high-power monolithic regulator family, designed specifically for compact, robust DC/DC conversion in space-constrained industrial and computing systems where external FETs and complex controllers add cost and failure risk.

FAQ

What is the maximum continuous output current achievable with the LT1268CT#PBF in a standard TO-220 heatsink configuration?

The LT1268CT#PBF supports up to 7.5A switch current electrically, but thermal limits govern practical output. With θ_JA = 50°C/W and 125°C max junction temperature, continuous dissipation must stay below ~2W. At 40% duty cycle and 0.18Ω R_DS(on), this yields ~5A continuous output in a well-heatsinked TO-220 layout - matching the derated curve in Figure 603 of the datasheet. The LT1268CT#PBF datasheet explicitly states IMAX = P/(RSW × DC) for thermal estimation.

Does the LT1268CT#PBF support synchronization to an external clock, and what is the required signal format?

Yes, the LT1268CT#PBF supports external synchronization via its VC pin. A TTL- or CMOS-compatible square wave (0V to ≥2.5V) applied to VC overrides the internal oscillator. The sync frequency must fall within 120–180kHz to ensure stable operation; frequencies outside this range may cause erratic switching or dropout. This capability is documented in the LT1268CT#PBF datasheet under "Externally Synchronized Operation" and referenced to the LT1072 implementation.

How does the LT1268CT#PBF achieve ±1% output voltage accuracy, and what external components are critical?

The LT1268CT#PBF achieves ±1% output accuracy using its 1.244V ±9mV reference voltage (LT1268B variant) combined with a precision resistor divider. The datasheet specifies that 0.1% tolerance resistors on the FB network are mandatory; additionally, load current must be sourced from the case (VIN pin) and FB ground must be routed separately from power ground to avoid IR drop errors. These requirements are explicitly called out in Note 4 of the LT1268CT#PBF electrical characteristics table.

Can the LT1268CT#PBF be used in flyback topology, and what protection features apply in that configuration?

Yes, the LT1268CT#PBF is explicitly qualified for flyback operation per its product description and application notes. In flyback mode, its internal 60V switch breakdown rating and cycle-by-cycle current limiting protect against transformer reset spikes and overload conditions. The self-protected architecture includes automatic foldback during overloads and thermal shutdown at 140°C short-circuit junction temperature - all confirmed in the Absolute Maximum Ratings and Features sections of the LT1268CT#PBF datasheet.

What is the purpose of the case-connected VIN pin on the LT1268CT#PBF TO-220 package, and how should it be mounted?

The metal tab (case) of the LT1268CT#PBF TO-220 package is electrically connected to the VIN pin, enabling direct thermal coupling to a heatsink without insulating hardware - but requiring electrical isolation if the heatsink is grounded. Mounting must use thermal compound and mechanical pressure per Linear's recommended torque (5–7 in-lb); insufficient contact raises θ_JC and risks thermal runaway. This construction is defined in the LT1268CT#PBF package outline drawing and thermal section.