Texas Instruments TPS61121PW

Overview

TPS61121PW from Texas Instruments is a synchronous boost converter with integrated 200-mA LDO, designed for single-cell Li-Ion/Li-Polymer or dual–quadruple alkaline/NiMH battery-powered portable systems. It delivers a fixed 3.3-V DC-DC output (≥250 mA at 1.8-V input) and a fixed 1.5-V LDO output (≥120 mA), operating from 1.8 V to 5.5 V input with 95% peak efficiency and 40-µA typical quiescent current.

For engineers reviewing the TPS61121PW datasheet, TPS61121PW pinout, TPS61121PW application, or TPS61121PW equivalent, key selection considerations include its dual-output architecture (boost + post-regulated LDO), low-battery detection interface (LBI/LBO), power-good signaling (PGOOD), thermal shutdown, and compatibility with compact TSSOP-16 layout in space-constrained handheld devices.

Technical Context

The TPS61121PW implements a fixed-frequency (500 kHz nominal), multiple feed-forward PWM controller with synchronous rectification using integrated N- and P-channel MOSFETs. It senses input voltage, output voltage, NMOS switch voltage drop, and peak switch current (1300 mA typ.) to dynamically adjust duty cycle and maintain regulation across wide load and input ranges.

Its dual-ground architecture separates signal ground (GND) from power ground (PGND) to prevent noise coupling, while an integrated antiringing switch suppresses SW-node oscillation in discontinuous conduction mode. The LDO stage supports back-bias operation and independent enable control (LDOEN), allowing seamless switchover between battery-derived and external power sources.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm body), thermally enhanced with exposed pad not connected internally; requires PCB thermal relief and GND connection per TI layout guidelines.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output boost+LDO applications.

Compared with TPS61121PW, TPS61221DRCR omits the LDO entirely - eliminating dual-rail functionality but shrinking size and cost; MAX8642ETA+ provides similar dual-rail capability but lacks integrated battery monitoring and power-good, increasing system-level component count and validation effort.

Availability

TPS61121PW is available at Aetrix Electronics and suitable for portable medical devices, handheld industrial scanners, USB-powered test equipment, and consumer audio products requiring stable component supply across long production lifecycles.

Supply support for TPS61121PW 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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in power management IC design and high-volume manufacturing reliability.

The TPS6112x product line was engineered specifically for ultra-low-power, dual-rail portable electronics - integrating boost conversion, post-regulation, battery supervision, and fault signaling into a single TSSOP/VQFN package to reduce system complexity and bill-of-materials cost.

FAQ

What is the minimum input voltage required for TPS61121PW to regulate its 3.3-V output?

The TPS61121PW maintains regulation of its fixed 3.3-V DC-DC output down to a 1.8-V input voltage under typical conditions. Below 1.8 V, undervoltage lockout disables the device to prevent malfunction. At 1.8-V input, it delivers ≥250 mA to the 3.3-V rail with >85% efficiency, enabling full utilization of single-cell Li-Ion discharge curves.

Can the TPS61121PW operate with the LDO enabled while the boost converter is disabled?

Yes, the TPS61121PW supports independent control: the LDO can remain active (via LDOEN = high) even when the boost converter is disabled (EN = low). This allows the LDO to supply its 1.5-V output from an external source (e.g., USB 5 V applied to LDOIN) while the boost stage is off - enabling flexible power-source arbitration without additional external switches.

How does the low-battery detection (LBI/LBO) function on the TPS61121PW?

The TPS61121PW's LBI pin accepts a scaled-down battery voltage; when that voltage falls below 500 mV (with 10-mV hysteresis), the open-drain LBO pin pulls low. The function is active only when EN = high. For example, a 1-MΩ/1-MΩ resistor divider on a 3.6-V battery yields 1.8 V at LBI - triggering LBO when battery drops to ~2.7 V, providing early warning before system brownout.

Does the TPS61121PW require external components for stable operation?

Yes, the TPS61121PW requires external components per TI's recommended schematic: a 10-µH power inductor (e.g., Sumida CDRH73–100), 10-µF ceramic output capacitor on VOUT, 2.2-µF ceramic on LDOOUT, 100-µF low-ESR tantalum on input, and 2.2-µF ceramic on LDOIN. These ensure stability, transient response, and EMI compliance - omitting any compromises efficiency or reliability.

What thermal considerations apply to the TPS61121PW in TSSOP-16 package?

The TPS61121PW in TSSOP-16 has a junction-to-ambient thermal resistance (R_θJA) of 100.5°C/W. To avoid thermal shutdown at 125°C junction, average power dissipation must stay below ~500 mW with standard 2-layer PCB copper. TI recommends 250 mm² of 1-oz copper connected to PGND and GND pins, plus thermal vias under the exposed pad area (if used per layout guidelines) to improve heat transfer.