Analog Devices Inc. LT1949-1EMS8#TRPBF

Overview

LT1949-1EMS8#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode step-up DC/DC converter with a 1A, 0.5Ω NPN internal switch, 1.1MHz switching frequency, and 30V switch rating. It generates 10V at 175mA from a 3.3V input and is designed for LCD bias supplies in portable electronics requiring compact, low-noise, ceramic-capacitor-compatible solutions.

For engineers reviewing the LT1949-1EMS8#TRPBF datasheet, LT1949-1EMS8#TRPBF pinout, LT1949-1EMS8#TRPBF application, or LT1949-1EMS8#TRPBF equivalent, key selection criteria include its 1.24V feedback reference, external compensation (VC pin), active low-battery detector (LBI/LBO), shutdown quiescent current of 50µA, and MSOP-8 package compatibility with layout-sensitive high-frequency boost topologies.

Technical Context

The LT1949-1EMS8#TRPBF employs peak-current-mode control with an integrated 1.1MHz oscillator and ramp compensation to prevent subharmonic oscillation above 50% duty cycle. Its error amplifier features 140–480 µmhos transconductance and 700 V/V voltage gain, driven by an external RC network on the VC pin for loop stability with low-ESR ceramic output capacitors.

It integrates a dedicated low-battery detector with a 200mV ±5% internal reference, active during shutdown, and uses a logic-level SHDN pin (1.4V high threshold, 0.4V low) to disable switching while retaining LBO functionality. The 30V-rated switch supports output voltages up to 28V with single-inductor topology.

Key Specifications

Pinout & Package

LT1949-1EMS8#TRPBF is housed in an 8-lead plastic MSOP package (3.0mm × 3.0mm × 0.86mm height), optimized for thermal performance (θ_JA = 120°C/W) and high-frequency layout integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost converter applications.

Compared with LT1317BEMS8#TRPBF and LT1930ES5#TRPBF, the LT1949-1EMS8#TRPBF uniquely combines 1A current capability, active low-battery detection, and external compensation in an MSOP-8 footprint-enabling robust, feature-rich boost conversion where runtime monitoring and output stability are critical.

Availability

LT1949-1EMS8#TRPBF is available at Aetrix Electronics and suitable for LCD bias supplies, GPS receiver power management, and portable medical diagnostic equipment requiring stable component supply and long-term lifecycle support.

Supply support for LT1949-1EMS8#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 full product support, datasheet archives, and application engineering for legacy Linear parts including the LT1949 family.

The LT1949 series was designed specifically for compact, high-efficiency boost conversion in space- and noise-sensitive applications such as LCD bias generation and portable instrumentation, emphasizing integration, low IQ, and built-in system monitoring.

FAQ

What is the minimum input voltage required for LT1949-1EMS8#TRPBF to regulate a 10V output?

The LT1949-1EMS8#TRPBF operates with input voltages as low as 1.5V, but regulation of a 10V output requires sufficient headroom for the internal switch and diode drop. With a 3.3V nominal input (as shown in Figure 1), the LT1949-1EMS8#TRPBF delivers 10V at 175mA. Below ~2.2V input, duty cycle approaches maximum and regulation may degrade; datasheet testing confirms stable operation down to 1.7V across temperature.

Does LT1949-1EMS8#TRPBF support ceramic output capacitors, and what is the recommended value?

Yes, the LT1949-1EMS8#TRPBF is explicitly designed for ceramic output capacitors. The datasheet recommends 3.3µF ceramic (e.g., Taiyo Yuden LMK325BJ335MD) placed close to the SW and GND pins. This value ensures adequate energy storage and low impedance at 1.1MHz, minimizing output ripple without requiring bulk electrolytic capacitors.

How does the low-battery detector in LT1949-1EMS8#TRPBF function during shutdown mode?

The low-battery detector in LT1949-1EMS8#TRPBF remains fully active during shutdown: the 200mV internal reference and LBI comparator continue operating, and LBO will assert low when the LBI voltage falls below threshold. This allows host systems to monitor battery health even when the main boost converter is disabled, with only 50µA total shutdown current drawn by the LT1949-1EMS8#TRPBF.

What is the purpose of the VC pin on LT1949-1EMS8#TRPBF, and how is it configured?

The VC pin on LT1949-1EMS8#TRPBF is the error amplifier compensation node. It requires an external series RC network (e.g., 30kΩ resistor + 330pF capacitor) connected to ground to stabilize the control loop. This configuration allows designers to tailor phase margin and transient response for specific output capacitor ESR and load dynamics-critical when using low-ESR ceramics.

Is LT1949-1EMS8#TRPBF pin-compatible with other members of the LT1949 family?

Yes, LT1949-1EMS8#TRPBF shares the same 8-lead MSOP package and pinout as LT1949EMS8#TRPBF (600kHz version) and is explicitly stated as pin-for-pin compatible with LT1317B. Differences lie in switching frequency, current limit, and internal oscillator design-not physical layout-so PCBs designed for LT1317B can accept LT1949-1EMS8#TRPBF without modification.