Analog Devices Inc. LT1109CZ-12#PBF

Overview

LT1109CZ-12#PBF from Analog Devices (formerly Linear Technology) is a fixed-output 12V step-up DC/DC converter in a 3-lead TO-92 package, designed for flash memory VPP programming and low-power 5V-to-12V conversion. It delivers up to 60mA output current from a 5V input, features 120kHz oscillator frequency, 1.6V minimum start-up voltage, and 320µA quiescent current - enabling operation from two-cell alkaline or NiMH batteries.

For engineers reviewing the LT1109CZ-12#PBF datasheet, LT1109CZ-12#PBF pinout, LT1109CZ-12#PBF application, or LT1109CZ-12#PBF equivalent, key selection criteria include fixed 12V output tolerance (±4.2%), TO-92 thermal limitations (θ_JA = 160°C/W), absence of shutdown control (Z-package only), and compatibility with off-the-shelf 33µH surface-mount inductors.

Technical Context

The LT1109CZ-12#PBF implements a gated-oscillator boost topology with internal 1.25V reference and comparator-based feedback. Its bootstrapped power architecture draws operating current from the VOUT pin, eliminating need for external bias supply. The device uses no frequency compensation components due to built-in hysteresis (8–12.5mV) in the error amplifier.

It operates in discontinuous conduction mode with fixed 4.2µs typical switch ON time and 50% nominal duty cycle at full load. Output regulation is achieved by cycling the internal 1.2A NPN switch at 120kHz, storing energy in an external inductor and transferring it via external Schottky diode to the output capacitor.

Key Specifications

Pinout & Package

LT1109CZ-12#PBF is supplied in a 3-lead TO-92 plastic package (Z package), with bottom-view pinout optimized for through-hole mounting and thermal dissipation in low-power applications. Package thermal resistance is θ_JA = 160°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-up DC/DC converter applications.

Compared with LT1109CZ-12#PBF, the LT1109CN8-12 adds controllable shutdown but increases board area and component count, while the LT1301CS8-12 trades TO-92 simplicity for higher output current and lower shutdown IQ - making LT1109CZ-12#PBF optimal for cost-sensitive, space-constrained, fixed-output VPP generation where 60mA suffices.

Availability

LT1109CZ-12#PBF is available at Aetrix Electronics and suitable for flash memory programming, disk drive auxiliary power, and battery-powered peripheral applications requiring stable component supply, long-lifecycle support, and TO-92 form factor compatibility.

Supply support for LT1109CZ-12#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 its portfolio of high-performance analog and power management ICs with emphasis on reliability and long-term support.

The LT1109 product line was designed specifically for low-cost, micropower DC/DC conversion in battery-operated and space-constrained systems - prioritizing minimal external component count, ultra-low quiescent current, and robust start-up behavior under marginal input conditions.

FAQ

What is the maximum output current capability of the LT1109CZ-12#PBF?

The LT1109CZ-12#PBF delivers up to 60mA continuous output current when supplied from a 5V input, as specified in the datasheet's electrical characteristics table. This rating assumes proper thermal management using the TO-92 package's 160°C/W junction-to-ambient thermal resistance and use of recommended external components (33µH inductor, Schottky diode, 22µF/16V output capacitor). Exceeding 60mA may cause thermal shutdown or output voltage droop.

Does the LT1109CZ-12#PBF include a shutdown control pin?

No, the LT1109CZ-12#PBF does not include a shutdown control pin. Shutdown functionality is only available on the 8-pin N8 and S8 package variants (e.g., LT1109CN8-12, LT1109CS8-12). The Z-package (TO-92) version is a fixed-function device with no enable/disable logic interface - it operates continuously when valid input voltage is applied to the VOUT pin.

Which inductor value is required for stable operation of the LT1109CZ-12#PBF?

The LT1109CZ-12#PBF requires a 33µH surface-mount inductor rated for ≥80mA DC current, such as Sumida CD54-330LC or Coiltronics CTX33-1. This value is explicitly validated in the datasheet's typical application circuits and ensures proper energy transfer at the 120kHz oscillator frequency while maintaining discontinuous conduction mode and staying within the 1.2A peak switch current limit.

Can the LT1109CZ-12#PBF operate from a single 3.7V Li-ion cell?

Yes, the LT1109CZ-12#PBF can operate from a single 3.7V Li-ion cell, but only during the cell's upper voltage range (≥3.7V). Its minimum start-up voltage is 1.6V at the VOUT pin, but sustained regulation requires sufficient input headroom: the datasheet specifies 3V ≤ VIN ≤ 12V for the -12 variant. Below ~3.2V, output current capability degrades rapidly, and regulation is lost below 3V input.

What is the output voltage tolerance of the LT1109CZ-12#PBF over temperature and line variations?

The LT1109CZ-12#PBF has a guaranteed output voltage tolerance of ±4.2% (11.52V to 12.55V) across the full 0°C to 70°C operating temperature range and 3V to 12V input voltage range. This specification includes initial accuracy, line regulation, load regulation, and temperature drift - all tested and characterized per the datasheet's ELECTRICAL CHARACTERISTICS table.