Texas Instruments TPS61221DCKR

Overview

TPS61221DCKR from Texas Instruments is a fixed-output 3.3 V synchronous boost converter optimized for ultra-low-input-voltage battery-powered systems. It operates from 0.7 V to 5.5 V input, delivers up to 126 mA output current at 2.4 V input, achieves ≥90% efficiency at 50 mA load, and features 5.5 μA quiescent current - enabling multi-year operation in coin-cell or single-alkaline applications such as portable medical sensors and LED indicators.

For engineers reviewing the TPS61221DCKR datasheet, TPS61221DCKR pinout, TPS61221DCKR application, or TPS61221DCKR equivalent, this page provides verified technical context, real-world performance boundaries (e.g., startup at 0.7 V, 3.3 V ±3.1% output tolerance), package-aware layout guidance, and validated alternative options for low-power boost conversion where input voltage may dip below 1 V.

Technical Context

The TPS61221DCKR implements a hysteretic current-mode control architecture with synchronous rectification, using two integrated MOSFETs (R_DS(on) = 600 mΩ main switch, 700 mΩ rectifier) to minimize conduction loss at ultra-low input voltages. Its self-oscillating topology eliminates external compensation and supports wide-ranging external components - including 4.7 µH inductors and 10 µF ceramic capacitors - while maintaining stability across discontinuous-to-continuous current transitions.

Startup is managed by an internal oscillator that enables operation down to 0.7 V input, transitioning to normal hysteretic mode once V_OUT reaches ~1.8 V. Protection includes undervoltage lockout (0.7 V threshold), overvoltage clamping at 6.0–7.5 V, and thermal shutdown at 140 °C with 20 °C hysteresis - all implemented without external circuitry.

Key Specifications

Pinout & Package

TPS61221DCKR is housed in a 6-pin SC-70 (DCK) package measuring 2.00 mm × 1.25 mm, optimized for minimal PCB footprint in wearables and compact IoT devices. Thermal resistance R_θJA is 231.2 °C/W, requiring minimal copper pour for ambient operation up to 125 °C junction temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS61220DCKR and MAX17222ELT+T, the TPS61221DCKR delivers the highest guaranteed output current (126 mA) at low input voltages while retaining the lowest risk of BOM or layout change - making it optimal for production designs targeting robust 3.3 V delivery from marginal sources.

Availability

TPS61221DCKR is available at Aetrix Electronics and suitable for portable medical sensors, low-power LED indicators, energy-harvesting sensor nodes, and consumer wearables requiring stable component supply across long-lifecycle programs.

Supply support for TPS61221DCKR 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 ICs for battery-constrained applications.

The TPS6122x product line was designed specifically for ultra-low-input-voltage boost conversion in space- and energy-sensitive systems - targeting single-cell battery operation, coin-cell longevity, and minimal external component count.

FAQ

What is the minimum input voltage required for TPS61221DCKR to start up and regulate?

The TPS61221DCKR starts up and regulates at a minimum input voltage of 0.7 V, as confirmed in the datasheet's Recommended Operating Conditions and Electrical Characteristics tables. This enables reliable operation from deeply discharged alkaline, NiMH, or energy-harvesting sources. The device uses an internal startup oscillator to initiate switching before transitioning to normal hysteretic mode once V_OUT reaches ~1.8 V. Below 0.7 V, the TPS61221DCKR remains inactive.

Does TPS61221DCKR require external feedback resistors to set its output voltage?

No, the TPS61221DCKR does not require external feedback resistors. It is a fixed-output variant with an internally trimmed 3.3 V regulator. The FB pin is internally connected to the output voltage divider and must be shorted directly to the VOUT pin per the datasheet's Pin Configuration and Applications sections. Adding external resistors would disrupt regulation and is not supported for the TPS61221DCKR.

What happens to the output when TPS61221DCKR is disabled via the EN pin?

When the EN pin is pulled low, the TPS61221DCKR enters shutdown mode: switching stops, internal control circuitry powers down, and quiescent current drops to 0.2–0.5 μA. However, the output remains partially active due to the body diode of the internal rectifying MOSFET - allowing VIN to pass through to VOUT (with ~0.3–0.5 V drop). This pass-through behavior avoids the need for an external diode in applications requiring backup power path.

Can TPS61221DCKR drive a white LED directly from a single 1.5 V alkaline cell?

Yes, the TPS61221DCKR can drive a white LED directly from a single 1.5 V alkaline cell. With its 0.7 V startup capability and 3.3 V fixed output, it provides sufficient forward voltage for standard white LEDs (typically 2.8–3.4 V). At 1.2 V input, it delivers up to ~60 mA output current - adequate for indicator LEDs. Efficiency exceeds 85% under these conditions, minimizing heat and maximizing runtime as the cell discharges to 0.8 V.

What thermal considerations apply to TPS61221DCKR in a 2 mm × 1.25 mm SC-70 package?

The TPS61221DCKR has a junction-to-ambient thermal resistance (R_θJA) of 231.2 °C/W in the SC-70 package. To maintain safe operation up to 125 °C junction temperature, PCB layout must include adequate copper area under the exposed pad (if present) and thermal vias to inner layers. At 126 mA output with 1.2 V input, power dissipation is ~30 mW - resulting in <7 °C rise above ambient with minimal copper, but derating is advised above 85 °C ambient or under sustained high load.