Texas Instruments TPS61251DSGT

Overview

TPS61251 from Texas Instruments is a synchronous boost converter IC designed for battery backup capacitor charging, operating as a resistor-programmable constant-current source with 2.3 V to 6.0 V input, adjustable 3 V to 6.5 V output, ±10% input current limit accuracy at 500 mA, and 3.5 MHz switching frequency-used in Li-ion-powered SSDs and RF-PA buffers.

For engineers reviewing the TPS61251 datasheet, TPS61251 pinout, TPS61251 application, or TPS61251 equivalent, key selection considerations include its snooze-mode 2 µA quiescent current, programmable 100–1500 mA input current limit, power-good signaling during shutdown, 100% duty-cycle operation when VIN > VOUT, and integrated reverse-current protection for bulk-capacitor backup systems.

Technical Context

The TPS61251 employs an adaptive on-time valley-current-mode control architecture with quasi-constant 3.5 MHz switching under moderate-to-heavy loads and automatic transition to PFM mode at light loads. Its internal averaging circuit directly regulates average input current via valley current sensing across the synchronous rectifier, enabling ±10% accuracy at 500 mA without external current-sense resistors.

It integrates undervoltage lockout (2.0 V falling, 2.1 V rising), input overvoltage protection (6.4–6.5 V), thermal regulation (active above 110°C), and thermal shutdown (140°C). The power-good (PG) open-drain output remains functional during shutdown, monitoring VOUT down to 2.3 V while maintaining high-impedance state until VOUT falls below 2.0 V.

Key Specifications

Pinout & Package

The TPS61251 is housed in an 8-pin WSON package (DSG suffix) with a 2.0 mm × 2.0 mm body and exposed thermal pad that must be soldered to GND for thermal and mechanical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS61252DSGT and MAX17222ETA+T, the TPS61251DSGT uniquely combines adjustable output voltage, 1500 mA programmable input current limit, power-good signaling during shutdown, and 3.5 MHz operation in a 2×2 mm WSON-making it the only option capable of robust Farad-range capacitor charging for high-peak-power portable systems.

Availability

TPS61251DSGT is available at Aetrix Electronics and suitable for SSD power backup, RF-PA buffer supply, Li-ion battery backup, audio codec power rails, and portable medical device hold-up requiring stable component supply across production lifecycles.

Supply support for TPS61251DSGT 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 delivering analog, embedded processing, and connectivity solutions with emphasis on power management innovation and long-term product support.

The TPS61251 belongs to TI's high-efficiency boost converter product line, engineered specifically for capacitor-based battery backup systems in portable electronics requiring precise input current limiting and ultra-low quiescent power.

FAQ

What is the minimum input voltage required for TPS61251DSGT to start switching?

The TPS61251DSGT incorporates undervoltage lockout (UVLO) with a falling threshold of 2.0 V and hysteresis of 100 mV. It begins switching only when VIN rises above 2.1 V. Below 2.0 V, the device remains fully disabled with load disconnected and PG in high-impedance state. This prevents erratic operation during battery brownout conditions and protects against excessive cell discharge.

How does the TPS61251DSGT implement current limiting without an external sense resistor?

The TPS61251DSGT uses internal valley current sensing across the synchronous rectifier's RDS(on) during off-time to regulate average input current. The ILIM pin sets a reference voltage that adjusts the valley current threshold dynamically. This achieves ±10% accuracy at 500 mA without external components-reducing BOM cost, board area, and power loss compared to shunt-based methods.

Can the TPS61251DSGT maintain power-good signaling after shutdown is asserted?

Yes-the TPS61251DSGT's PG output remains functional during shutdown. When EN is pulled low or VIN is removed, PG continues monitoring VOUT and asserts high as long as VOUT stays ≥95% of the programmed value. PG goes low only when VOUT drops below 2.3 V, providing unambiguous status of bulk capacitor charge level throughout discharge.

What happens to the TPS61251DSGT output when input voltage exceeds output voltage?

When VIN > VOUT, the TPS61251DSGT enters 100% duty-cycle mode: the PMOS switch remains continuously on, creating a low-impedance path. Output voltage follows VIN minus drop across the PMOS RDS(on) (200 mΩ) and inductor DCR. This minimizes dropout and preserves efficiency during input voltage surges or battery recovery, without disabling regulation or current limiting.

Does the TPS61251DSGT require external compensation components?

No-the TPS61251DSGT integrates all loop compensation and soft-start circuitry. Its adaptive slope-compensated current-mode control and internal error amplifier eliminate the need for external compensation networks. Designers only require the feedback divider (R1/R2), ILIM resistor, input/output capacitors, and inductor-reducing design complexity and validation effort.