Texas Instruments TPS65251-1RHAR

Overview

TPS65251-1RHAR from Texas Instruments is a triple-output synchronous buck converter IC with integrated high- and low-side MOSFETs, designed for 4.5–18 V input systems. It delivers 3 A continuous (3.5 A peak) on Buck 1 and 2 A continuous (2.5 A peak) on Bucks 2 and 3, supporting set-top boxes, DVRs, and automotive infotainment with adjustable 300 kHz–2.2 MHz switching frequency and 180° out-of-phase operation between Buck 1 and Bucks 2/3 to minimize input ripple.

For engineers reviewing the TPS65251-1RHAR datasheet, TPS65251-1RHAR pinout, TPS65251-1RHAR application, or TPS65251-1RHAR equivalent, key selection criteria include per-channel enable/soft-start pins, external current limit resistor configuration (RLIMx), ROSC-based frequency tuning, PGOOD sequencing behavior (1 s reset time), and VQFN-40 6 mm × 6 mm thermal performance (RθJA = 32.7°C/W).

Technical Context

The TPS65251-1RHAR implements peak current-mode control with internal slope compensation across all three buck channels, enabling stable loop response with simple RC compensation networks on COMP1–COMP3 pins. Each channel features independent feedback (FB1–FB3), soft-start (SS1–SS3), and enable (EN1–EN3) pins, allowing programmable power-up sequencing and load-specific optimization.

It supports dual operating modes: forced PWM for consistent ripple and automatic PFM/PWM transition (via LOW_P pin) to improve light-load efficiency. Input ripple reduction is achieved through fixed 180° phase shift between Buck 1 and Buck 2, while Buck 2 and Buck 3 operate in-phase - a topology confirmed in the functional block diagram and timing analysis.

Key Specifications

Pinout & Package

VQFN-40 (RHA) package, 6.00 mm × 6.00 mm body, 0.4 mm pitch, exposed thermal pad connected to GND. Designed for high-power density and efficient heat dissipation in space-constrained consumer and automotive applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS65251-2RHAR and TPS65251-3RHAR, the TPS65251-1RHAR provides the longest PGOOD assertion delay (1000 ms), making it optimal for systems requiring extended post-regulation verification before releasing reset - such as industrial DVRs with complex FPGA configuration or automotive displays needing stable backlight enable timing.

Availability

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

Supply support for TPS65251-1RHAR 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 decades of expertise in high-efficiency DC/DC conversion.

The TPS65251-x family is designed specifically for multi-rail consumer and automotive multimedia systems, integrating three high-current synchronous bucks with advanced sequencing, thermal management, and EMI-reduction features in a single compact package.

FAQ

What is the PGOOD assertion delay for TPS65251-1RHAR?

The TPS65251-1RHAR has a factory-set PGOOD reset time of 1000 ms. This delay begins after all three buck outputs reach ≥90% of their nominal voltage and sequencing completes. It ensures robust system-level reset timing for applications like DVRs and automotive displays where extended verification is required before processor release. The TPS65251-1RHAR variant is distinguished from TPS65251-2RHAR (32 ms) and TPS65251-3RHAR (256 ms) solely by this parameter.

How do I configure the switching frequency of TPS65251-1RHAR?

To configure the switching frequency of TPS65251-1RHAR, connect a resistor from the ROSC pin to GND. A 230 kΩ resistor sets 800 kHz; values from 50 kΩ to 600 kΩ yield 0.3–2.2 MHz. The device also supports external synchronization via the SYNC pin - but only after PGOOD is asserted. When not synchronizing, tie SYNC to GND. Frequency selection directly impacts inductor size, efficiency trade-offs, and EMI filter design.

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

Yes, TPS65251-1RHAR supports pre-biased output startup. Its current-mode architecture and internal soft-start circuitry prevent reverse current flow during turn-on when output capacitors are already charged. The SS pins use a 5 µA current source to ramp the feedback node, ensuring monotonic voltage rise even with pre-bias. This capability is validated in the datasheet's timing diagrams and is essential for hot-swap and multi-rail sequencing scenarios.

What are the thermal limitations of TPS65251-1RHAR in continuous operation?

TPS65251-1RHAR has a junction-to-ambient thermal resistance (RθJA) of 32.7°C/W in standard JEDEC PCB layout. With maximum recommended junction temperature of 125°C and ambient up to 85°C, it supports full 3 A/2 A continuous loading when using the exposed thermal pad tied to ≥4 cm² of inner/outer copper with ≥6 thermal vias. Thermal shutdown triggers at 160°C with 20°C hysteresis, ensuring safe recovery without latch-up.

How does the 180° out-of-phase operation between Buck 1 and Buck 2 reduce input ripple?

In TPS65251-1RHAR, Buck 1 and Buck 2 switch 180° out-of-phase while Buck 2 and Buck 3 are in-phase. This interleaving causes their input current ripple waveforms to partially cancel at the shared VIN node. Measured results show up to 40% reduction in RMS input ripple compared to in-phase operation - allowing smaller input bulk capacitors (e.g., 2 × 10 µF instead of 3 × 10 µF) and relaxed EMI filter requirements, directly lowering BOM cost and board area.