Analog Devices Inc. LTC3335IUDC#TRPBF

Overview

LTC3335IUDC#TRPBF from Analog Devices (formerly Linear Technology) is a nanopower buck-boost DC/DC converter with integrated precision coulomb counter, designed for ultra-low-power primary-cell battery applications. It delivers up to 50mA output current across eight pin-selectable voltages (1.8V–5V), operates down to 1.8V input, and draws only 680nA quiescent current in regulation - enabling multi-year operation in wireless sensors and remote monitors.

For engineers reviewing the LTC3335IUDC#TRPBF datasheet, LTC3335IUDC#TRPBF pinout, LTC3335IUDC#TRPBF application, or LTC3335IUDC#TRPBF equivalent, key selection criteria include its I²C-accessible coulomb counter with ±5% discharge accuracy, programmable 5–250mA peak input current, and 20-pin 3mm × 4mm QFN package with exposed PGND pad for thermal management.

Technical Context

The LTC3335IUDC#TRPBF implements a hysteretic buck-boost topology using four internal MOSFETs (A–D) in an H-bridge configuration, enabling seamless step-up/step-down conversion across 1.8V–5.5V input and 1.8V–5V output ranges. Regulation relies on sleep/wake thresholds with <3µs wake-up latency and zero-current switching detection to ensure accurate coulomb counting.

Its integrated coulomb counter measures accumulated battery discharge via AC(ON) time sampling synchronized to switch A/C conduction, storing results in a 50-bit counter chain (8 MSBs readable via I²C). The prescaler (M=0–15) and IPEAK setting jointly determine qLSB resolution - from 140.6mA·hr (5mA IPEAK) to 1793A·hr (250mA IPEAK, M=0) - supporting battery capacities from coin cells to large primary packs.

Key Specifications

Pinout & Package

The LTC3335IUDC#TRPBF is housed in a 20-lead plastic QFN package (3mm × 4mm, 0.75mm height) with an exposed power ground pad (Pin 21) that must be soldered to PCB for thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck-boost with fuel gauge applications.

Compared with MAX17055 and TPS62745, the LTC3335IUDC#TRPBF uniquely integrates both nanopower regulation and ±5% coulomb measurement in one 3mm × 4mm package - making it the sole option for space-constrained, long-life primary-cell systems requiring autonomous battery health reporting.

Availability

LTC3335IUDC#TRPBF is available at Aetrix Electronics and suitable for wireless sensors, remote monitors, and SmartMesh® endpoint designs requiring stable component supply over extended production lifecycles.

Supply support for LTC3335IUDC#TRPBF 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 legacy of high-performance power management ICs for precision, low-power, and reliability-critical applications.

The LTC3335IUDC#TRPBF belongs to Linear's nanopower DC/DC converter family, engineered specifically for energy-harvesting and primary-cell battery systems where multi-year operation and accurate battery telemetry are mandatory.

FAQ

What is the minimum input voltage required for LTC3335IUDC#TRPBF to regulate output?

The LTC3335IUDC#TRPBF supports input voltages as low as 1.8V while maintaining regulation across all eight output voltage options. This enables direct operation from depleted primary cells (e.g., alkaline down to 1.8V or LiSOCl₂ at end-of-life), eliminating the need for boost pre-regulators and extending usable battery capacity.

How does the coulomb counter in LTC3335IUDC#TRPBF achieve ±5% accuracy?

The LTC3335IUDC#TRPBF achieves ±5% total unadjusted coulomb counter accuracy by measuring AC(ON) time during each switch-A/C conduction cycle and compensating for IPEAK variation via internal calibration. This method avoids reliance on absolute current-sense resistor tolerance and remains valid across temperature, process, and supply variations - as verified in the Electrical Characteristics table under "Total Unadjusted Coulomb Counter Error".

Can LTC3335IUDC#TRPBF operate with a 5mA peak input current setting and still deliver 50mA output current?

No. At the 5mA IPEAK setting, the LTC3335IUDC#TRPBF is limited to ~1.8mA maximum continuous output current (per Figure 31). The 50mA output rating applies only when configured for higher IPEAK settings (e.g., 100mA or 250mA) and appropriate inductor selection - as specified in Table 8 and the "Available Output Current" parameter (20mA typical at 100mA IPEAK, VOUT = 3.3V).

What is the role of the exposed PGND pad (Pin 21) on the LTC3335IUDC#TRPBF package?

Pin 21 is the exposed power ground pad connected internally to the sources of all NMOS switches (B, C). It must be soldered to the PCB ground plane to provide low-impedance return paths for switching currents, minimize thermal resistance (θJA = 52°C/W), and reduce EMI. Leaving it unconnected degrades efficiency, increases junction temperature, and risks coulomb counter inaccuracy due to ground bounce.

Does LTC3335IUDC#TRPBF support I²C clock stretching or multi-master arbitration?

No. The LTC3335IUDC#TRPBF implements a standard-mode I²C slave interface (400kHz max) with fixed timing parameters (tLOW = 1.3µs, tHIGH = 0.6µs) and no clock stretching capability. It is designed for single-master systems where the host MCU initiates all transactions - consistent with its target use in resource-constrained sensor nodes without complex bus management requirements.