Texas Instruments TPS65251-1RHAT

Overview

TPS65251-1RHAT from Texas Instruments is a triple-output synchronous buck converter IC for multi-rail power management in wide-input industrial and consumer systems. It integrates three high-current DC/DC step-down regulators (3 A / 2 A / 2 A continuous), supports 4.5–18 V input, delivers adjustable outputs from 0.8 V to VIN−1 V, and features independent enable, soft-start, and current-limit pins per channel-used in set-top boxes and automotive infotainment head units.

For engineers reviewing the TPS65251-1RHAT datasheet, TPS65251-1RHAT pinout, TPS65251-1RHAT application, or TPS65251-1RHAT equivalent, key selection criteria include per-channel current limit adjustability via RLIM resistors, 300 kHz–2.2 MHz programmable switching frequency, 180° out-of-phase operation between Buck 1 and Buck 2/3 to reduce input ripple, and factory-default active-high PGOOD with 1-second reset timing specific to the -1 variant.

Technical Context

The TPS65251-1RHAT implements peak current-mode control with internal slope compensation across all three buck channels, enabling stable loop response with simple RC compensation networks on COMP pins. Each channel uses integrated high-side (95 mΩ Buck 1; 120 mΩ Buck 2/3) and low-side (50 mΩ Buck 1; 80 mΩ Buck 2/3) MOSFETs for synchronous conversion.

It supports dual operating modes: automatic PFM/PWM transition for light-load efficiency and forced PWM via LOW_P pin grounding. Input ripple is minimized by fixed 180° phase shift between Buck 1 and Buck 2, while Buck 2 and Buck 3 operate in-phase-enabling optimized input capacitor sizing and EMI reduction without external timing coordination.

Key Specifications

Pinout & Package

VQFN-40 (RHA) package, 6.0 mm × 6.0 mm body, 0.4 mm pitch, exposed thermal pad soldered to GND plane for enhanced thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-buck power management applications.

Compared with TPS65251-2RHAT and TPS65251-3RHAT, the TPS65251-1RHAT's 1000 ms PGOOD reset time provides maximum sequencing margin for complex multi-rail systems but adds latency unsuitable for time-sensitive applications-making variant selection a deliberate timing architecture decision, not a functional substitution.

Availability

TPS65251-1RHAT is available at Aetrix Electronics and suitable for set-top box, automotive infotainment, and security camera DVR applications requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for TPS65251-1RHAT 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, embedded processing, and power management technologies with over 50 years of innovation in high-reliability IC design.

The TPS65251-x family is designed for multi-rail power management in space-constrained consumer and industrial systems requiring high integration, flexible sequencing, and wide-input operation from unregulated 5–18 V sources.

FAQ

What is the PGOOD reset timing for TPS65251-1RHAT?

The TPS65251-1RHAT has a factory-programmed PGOOD reset time of 1000 ms. This means the open-drain PGOOD signal remains low for 1 second after all three buck outputs reach ≥90% of their target voltages, ensuring full sequencing completion before system release. This timing is unique to the -1 variant and differs from TPS65251-2RHAT (32 ms) and TPS65251-3RHAT (256 ms).

How do I set the switching frequency of TPS65251-1RHAT?

Set the switching frequency of TPS65251-1RHAT by connecting a resistor from the ROSC pin to ground. The value determines frequency: 230 kΩ yields 800 kHz (typical), while values from 50 kΩ to 600 kΩ support the full 300 kHz–2.2 MHz range. If synchronizing to an external clock, connect that signal to the SYNC pin-but note synchronization only engages after PGOOD assertion.

Can TPS65251-1RHAT operate with pre-biased outputs?

Yes, TPS65251-1RHAT supports pre-biased output startup. Its current-mode control architecture and internal soft-start circuitry allow safe ramp-up even when output capacitors retain residual voltage. The device does not force reverse current into the output, preventing potential damage to downstream components during hot-plug or partial-power-up scenarios.

What is the purpose of the LOW_P pin on TPS65251-1RHAT?

The LOW_P pin on TPS65251-1RHAT selects operating mode: grounded = forced PWM (constant frequency); pulled high = automatic PFM/PWM transition. In PFM mode, TPS65251-1RHAT skips pulses at light loads to improve efficiency while maintaining <2% output ripple-ideal for standby or low-power states in battery-backed or energy-conscious designs.

How is current limit adjusted per channel on TPS65251-1RHAT?

Current limit on TPS65251-1RHAT is adjusted per channel using external resistors on RLIM1, RLIM2, and RLIM3 pins. For Buck 1, a 75–300 kΩ resistor sets 100–300 mA peak current; for Buck 2/3, 1.1–5.1 A is set via resistor values specified in the datasheet's Figure 6-6, 6-12, and 6-18. This enables precise inductor selection and overcurrent protection tuning per rail.