Analog Devices Inc. LTC3255HDD#PBF

Overview

LTC3255HDD#PBF from Analog Devices (formerly Linear Technology) is a thermally enhanced, high-temperature-rated switched-capacitor step-down DC/DC converter delivering up to 50mA output current from a 4V–48V input, with adjustable regulated output from 2.4V to 12.5V and 16µA quiescent current in Burst Mode® regulation - optimized for 4mA–20mA current loop housekeeping power in industrial control and SCADA systems.

For engineers reviewing the LTC3255HDD#PBF datasheet, LTC3255HDD#PBF pinout, LTC3255HDD#PBF application, or LTC3255HDD#PBF equivalent, key selection considerations include its 2:1/1:1 automatic mode switching, integrated VIN shunt regulator for current-fed inputs, PGOOD open-drain output, reverse-polarity input tolerance (–52V), and –40°C to 150°C guaranteed junction temperature operation in the 3mm × 3mm 10-lead DFN package.

Technical Context

The LTC3255HDD#PBF implements a multimode capacitive charge pump with automatic 2:1 or 1:1 ratio selection based on VIN, VOUT, and load - enabling regulation across wide input ranges without inductors. Its internal shunt regulator, enabled by connecting SHUNT to BIAS, allows stable operation from high-impedance 4mA–20mA current sources while maintaining 2:1 conversion exclusively.

Burst Mode® regulation maintains 1.200V ±2.4mV feedback reference accuracy over temperature, with PGOOD asserting at ≥94% of final regulation voltage and releasing at ≤90%. Reverse-polarity protection limits VOUT excursion to one diode drop below GND when VIN < 0V, and thermal shutdown activates at ~175°C with hysteresis returning operation at ~165°C.

Key Specifications

Pinout & Package

Package: 10-lead (3mm × 3mm) plastic DFN with exposed thermal pad (Pin 11 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity (θJA = 43°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switched-capacitor step-down converter applications.

Compared with LTC3255HMSE#PBF, the LTC3255HDD#PBF offers superior board-area efficiency and identical high-temperature rating, while LTC3255IDD#PBF provides cost savings in non-extreme thermal environments but cannot replace LTC3255HDD#PBF in 150°C-critical applications.

Availability

LTC3255HDD#PBF is available at Aetrix Electronics and suitable for industrial control, factory automation, and SCADA system designs requiring stable component supply with guaranteed 150°C junction operation and current-loop compatibility.

Supply support for LTC3255HDD#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 precision analog and power management product lines with full technical and manufacturing continuity.

The LTC3255HDD#PBF belongs to Linear's high-reliability switched-capacitor DC/DC converter family, designed specifically for fault-tolerant, inductor-free power in current-fed and wide-input industrial applications.

FAQ

What is the maximum junction temperature specification for the LTC3255HDD#PBF?

The LTC3255HDD#PBF is guaranteed to operate over a junction temperature range of –40°C to +150°C. This high-temperature rating is validated per JEDEC standards and enables use in sealed enclosures, near heat sources, or in high-ambient industrial settings where standard-grade parts would derate or fail. Thermal design must ensure power dissipation keeps actual junction temperature within this limit.

How does the LTC3255HDD#PBF achieve current multiplication in 4mA–20mA current loops?

The LTC3255HDD#PBF achieves current multiplication by enabling its VIN shunt regulator (via SHUNT-to-BIAS connection), which locks the charge pump in 2:1 mode and draws only the necessary current from the loop to maintain regulation. For example, with a 4mA input and 3.3V output, the LTC3255HDD#PBF delivers up to 7.4mA continuously - effectively doubling usable current without violating loop compliance.

Can the LTC3255HDD#PBF operate with input voltages below 4V?

No - the LTC3255HDD#PBF has a minimum specified input voltage of 4V per its absolute ratings and electrical characteristics. Below 4V, undervoltage lockout prevents operation, and internal circuitry may not bias correctly. Attempting sub-4V operation risks failure to regulate or erratic behavior; no characterization data exists for operation below 4V.

What flying capacitor value is required for full 50mA output capability with the LTC3255HDD#PBF?

To achieve the full 50mA output current rating, the LTC3255HDD#PBF requires a flying capacitor of at least 0.4µF capacitance over temperature and bias - typically implemented using a 1µF X5R/X7R ceramic capacitor rated ≥(VOUT + 1V). Lower values reduce available output current and may cause regulation loss under load.

Is the LTC3255HDD#PBF pin-compatible with other variants like LTC3255EMSE#PBF?

Yes - the LTC3255HDD#PBF shares identical pin functions and electrical behavior with all LTC3255 variants, including LTC3255EMSE#PBF. However, package type (DFN vs MSOP), thermal resistance (43°C/W vs 40°C/W), and temperature grade (–40°C to 150°C vs –40°C to 125°C) differ. Layout and thermal design must match the specific package; electrical substitution is valid only within rated temperature limits.