Analog Devices Inc. LTC3129IMSE-1#TRPBF

Overview

LTC3129IMSE-1#TRPBF from Analog Devices (formerly Linear Technology) is a 200mA synchronous buck-boost DC/DC converter with 1.3µA quiescent current, fixed 1.2MHz PWM switching, and eight user-selectable fixed output voltages (2.5V–15V). It features maximum power point control (MPPC), accurate RUN pin threshold (1.22V typ), and seamless mode transitions-ideal for energy-harvesting systems powered by photovoltaic panels or low-voltage batteries.

For engineers reviewing the LTC3129IMSE-1#TRPBF datasheet, LTC3129IMSE-1#TRPBF pinout, LTC3129IMSE-1#TRPBF application, or LTC3129IMSE-1#TRPBF equivalent, key selection criteria include its 1.92V–15V input range, MPPC programmability, 16-pin MSOP package thermal performance (θJA = 40°C/W), and Burst Mode vs. fixed-frequency PWM operation trade-offs.

Technical Context

The LTC3129IMSE-1#TRPBF employs average current mode control with an internal transconductance error amplifier and oscillator-synchronized duty-cycle modulation. Its four-NMOS switch topology enables continuous regulation when VIN < VOUT (boost), VIN > VOUT (buck), or VIN ≈ VOUT (buck-boost boundary), with no subharmonic oscillation or output transients during mode transitions.

It integrates internal loop compensation, soft-start (3ms), and an on-chip voltage divider for output selection via VS1–VS3 pins. The MPPC function servo-controls VIN to a programmable voltage (1.175V reference) using external resistors, while the RUN comparator provides hysteresis (80mV typ) for predictable turn-on at user-defined thresholds.

Key Specifications

Pinout & Package

Package: 16-lead plastic MSOP (3mm × 4.9mm), thermally enhanced with exposed PGND pad (Pin 17) requiring PCB soldering for θJA = 40°C/W performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck-boost regulator applications.

Compared with LTC3129EMSE-1#TRPBF, the LTC3129IMSE-1#TRPBF offers guaranteed operation down to –40°C and superior thermal performance; compared with LTC3129IUD-1#TRPBF, it delivers 40% lower thermal resistance in the same footprint class, enabling full 200mA output in space-constrained industrial designs.

Availability

LTC3129IMSE-1#TRPBF is available at Aetrix Electronics and suitable for industrial wireless sensor nodes, solar panel post-regulators, and intrinsically safe power supplies requiring stable component supply, long-lifecycle support, and guaranteed extended-temperature performance.

Supply support for LTC3129IMSE-1#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 with rigorous automotive and industrial qualification.

The LTC3129 family was designed specifically for ultra-low-power energy harvesting and battery-backed systems where seamless buck-boost regulation, nanoscale quiescent current, and programmable MPPC are mandatory.

FAQ

What is the minimum input voltage required to start up the LTC3129IMSE-1#TRPBF?

The LTC3129IMSE-1#TRPBF has a guaranteed startup voltage of 2.42V (typical 2.25V) when VCC is unpowered. Once running, it sustains regulation down to 1.92V input due to back-driven VCC operation-enabling compatibility with partially discharged alkaline or NiMH cells. This behavior is confirmed in the Electrical Characteristics table under "VIN Start-Up Voltage" and "Input Voltage Range".

How does the MPPC function work on the LTC3129IMSE-1#TRPBF, and what external components are needed?

The MPPC pin on the LTC3129IMSE-1#TRPBF connects to a resistor divider from VIN to GND, setting a target input voltage (VIN = 1.175V × [1 + R_top/R_bottom]). When load demand exceeds source capability, the controller reduces inductor current to hold VIN at that setpoint-maximizing power transfer. No active components are required; only two precision resistors referenced to the 1.175V internal MPPC threshold.

Can the LTC3129IMSE-1#TRPBF operate with an output voltage higher than its input voltage?

Yes-the LTC3129IMSE-1#TRPBF is a true buck-boost converter and regulates VOUT above, below, or equal to VIN. In boost mode (e.g., VIN = 2.5V → VOUT = 5V), it uses SW1 and SW2 with BST1/BST2 bootstrapping to sustain gate drive. The block diagram and Figure 1 power stage schematic confirm four-NMOS topology enabling bidirectional voltage conversion without external diodes or transformers.

What is the purpose of the exposed pad (Pin 17) on the LTC3129IMSE-1#TRPBF MSOP package?

The exposed pad (Pin 17) on the LTC3129IMSE-1#TRPBF is electrically connected to PGND and serves dual functions: (1) primary high-current return path for switch currents, and (2) thermal conduction path to the PCB ground plane. Per the datasheet, it must be soldered to a thermal pad on the PCB to achieve the specified θJA = 40°C/W; omitting this connection degrades thermal performance by >2× and risks thermal shutdown under load.

How do I select between Burst Mode and fixed-frequency PWM operation on the LTC3129IMSE-1#TRPBF?

Set the PWM pin (Pin 8) to GND for Burst Mode (1.3µA IQ, best for battery life) or tie it to VCC for fixed 1.2MHz PWM (lower output ripple, deterministic frequency). The datasheet confirms automatic mode transition: even with PWM = GND, the LTC3129IMSE-1#TRPBF switches to PWM mode above ~20–50mA load (depending on VIN/VOUT) to maintain regulation-no external control logic required.