Analog Devices Inc. LT1305CS8#PBF

Overview

LT1305CS8#PBF from Analog Devices (formerly Linear Technology) is a micropower step-up DC/DC converter with integrated low-battery detector, designed for 2-cell to 3-cell alkaline/NiMH input (1.8V–4.5V) delivering regulated 5V at up to 400mA. It features Burst Mode™ operation, 120µA quiescent current, 1.24V feedback reference, and an open-collector LBO output that asserts low at 1.24V on the LBI pin - used in portable instruments and EL panel drivers.

For engineers reviewing the LT1305CS8#PBF datasheet, LT1305CS8#PBF pinout, LT1305CS8#PBF application, or LT1305CS8#PBF equivalent, key selection criteria include input voltage range (1.8V min), peak switch current (2.0A typ), low-battery trip accuracy (±30mV), SO-8 thermal resistance (θ_JA = 80°C/W), and compatibility with surface-mount inductors like Coilcraft DO3316-103.

Technical Context

The LT1305CS8#PBF employs a hysteretic current-mode Burst Mode™ architecture with a 120–185kHz oscillator, enabling ultra-low quiescent current during light loads while maintaining regulation via periodic switching bursts. Its internal 2A NPN switch features 140–280mV saturation voltage at 1A, and the feedback loop uses a precision 1.24V ±1% reference with 6–12.5mV hysteresis.

Low-battery detection operates independently of regulation: the LBI comparator monitors external voltage divider output and drives open-drain LBO low when input falls below 1.24V (±30mV), with no hysteresis unless externally added. Shutdown control (SHDN) reduces total supply current to ≤10µA and disables both regulator and detector.

Key Specifications

Pinout & Package

LT1305CS8#PBF is housed in an 8-lead plastic SOIC (SO-8) package with standard 1.27mm pitch, JEDEC MS-012AC compliant, and rated for 0°C to 70°C ambient operation. PGND and GND are separate pins but must be tied together under the package for optimal noise and thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1303CS8#PBF and MAX756CPA+, the LT1305CS8#PBF uniquely combines 400mA output, integrated low-battery detection, and SO-8 packaging - enabling single-chip power + supervision in space- and component-constrained portable designs.

Availability

LT1305CS8#PBF is available at Aetrix Electronics and suitable for portable instruments, EL panel drivers, medical sensors, and wireless remote terminals requiring stable component supply with long-term lifecycle support.

Supply support for LT1305CS8#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 technical and manufacturing continuity for all Linear legacy products including the LT1305 series.

The LT1305 belongs to Linear's micropower DC/DC converter product line, engineered specifically for battery-operated portable equipment where extended runtime, compact size, and integrated supervision are mandatory design requirements.

FAQ

What is the minimum input voltage required for LT1305CS8#PBF to start switching?

The LT1305CS8#PBF begins regulation at 1.8V input, with guaranteed operation down to this level per datasheet specifications. Below 1.8V, the internal reference and oscillator may not stabilize reliably. The device can maintain output during brief dips below 1.8V if sufficient input capacitance is present, but startup will not occur from cold at <1.8V. Designers should verify battery discharge curves to ensure sustained operation above this threshold throughout product lifetime.

Can LT1305CS8#PBF generate an output voltage other than 5V?

Yes, the LT1305CS8#PBF supports adjustable output voltages via the FB pin. By replacing the internal 5V feedback network with an external resistor divider, users can set V_OUT = 1.24V × (1 + R2/R1). The datasheet confirms this configuration in TA03 and TA06 schematics. Output accuracy depends on resistor tolerance and FB pin bias current (7–20nA), so 1% resistors and ≤100kΩ total divider impedance are recommended for ≤2% error.

How does the low-battery detector in LT1305CS8#PBF interact with shutdown mode?

The low-battery detector in LT1305CS8#PBF is disabled when SHDN is pulled high - LBO remains high-impedance regardless of LBI voltage. Only when SHDN is grounded (normal operation) does the LBI comparator activate and drive LBO low upon crossing 1.24V. This behavior is explicitly documented in Note 2 of the Electrical Characteristics table and ensures no false alerts during standby.

What inductor value is recommended for LT1305CS8#PBF when input is 2.0V?

For 2.0V input, the LT1305CS8#PBF datasheet specifies a 10µH inductor (e.g., Coilcraft DO3316-103) as optimal. This value balances peak current handling (2.0A), core saturation margin, and physical size. Using <5µH risks excessive ripple and reduced efficiency; >15µH increases turn-on time and may limit transient response. DCR must remain ≤50mΩ to avoid >100mV conduction loss at 400mA load.

Is LT1305CS8#PBF RoHS-compliant and lead-free?

Yes, LT1305CS8#PBF is RoHS-compliant and lead-free. The "#PBF" suffix denotes Pb-free (lead-free) packaging per Analog Devices' product marking convention. The SO-8 package uses matte tin lead finish, and the device meets JEDEC J-STD-020 moisture sensitivity level 3 (MSL3) requirements. Full compliance documentation, including substance declarations and test reports, is available through Analog Devices' quality portal.