Texas Instruments TPS54821RHLT

Overview

TPS54821RHLT from Texas Instruments is a 4.5 V to 17 V input, 8 A synchronous step-down DC/DC converter in a thermally enhanced 3.5 mm × 3.5 mm VQFN-14 package with exposed thermal pad. It integrates 26 mΩ high-side and 19 mΩ low-side MOSFETs, supports 200 kHz–1.6 MHz adjustable switching frequency, delivers ±1% 0.6 V reference accuracy over temperature, and features hiccup-mode overcurrent and thermal shutdown protection. It is used in high-performance point-of-load regulation for digital TV power supplies.

For engineers reviewing the TPS54821RHLT datasheet, TPS54821RHLT pinout, TPS54821RHLT application, or TPS54821RHLT equivalent, key selection considerations include its split-power-rail capability (PVIN = 1.6–17 V), monotonic start-up into pre-biased outputs, adjustable input UVLO via EN pin resistors, open-drain PWRGD monitoring with 92–106% VREF window, and BOOT-PH UVLO threshold of 2.1 V for reliable high-side gate drive.

Technical Context

The TPS54821RHLT implements constant-frequency peak current mode control with internal slope compensation to prevent subharmonic oscillation across full duty cycle range. Its transconductance error amplifier (1300 µA/V) compares VSENSE to the lower of SS/TR voltage or 0.6 V reference, enabling precise output regulation and tracking functionality.

It supports dual-input rail architecture: VIN (4.5–17 V) powers control circuitry while PVIN (1.6–17 V) supplies the power stage - enabling low-voltage intermediate bus operation. Protection includes cycle-by-cycle high-side current limiting (10.5–17 A), bidirectional low-side current limiting (sourcing: 9.5–15 A; sinking: 2–4 A), and thermal hiccup shutdown at 160–175 °C with 16384-cycle restart delay.

Key Specifications

Pinout & Package

TPS54821RHLT uses a 14-pin VQFN package (3.5 mm × 3.5 mm) with exposed thermal pad (Pin 15) requiring solder connection for thermal and electrical grounding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down converter applications.

Compared with TPS54821RHLT, TPS54824RHLT adds digital control at higher cost and size, while MP8772GQ-Z sacrifices configurability and split-rail capability for integration and price - making TPS54821RHLT optimal for analog-controlled, thermally constrained, or intermediate-bus designs.

Availability

TPS54821RHLT is available at Aetrix Electronics and suitable for digital TV power supplies, set-top boxes, and Blu-ray disc players requiring stable component supply, long-term industrial availability, and guaranteed traceable sourcing.

Supply support for TPS54821RHLT 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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and consumer markets.

The TPS54821RHLT belongs to TI's SWIFT™ family of high-current DC/DC converters, designed specifically for high-efficiency, space-constrained point-of-load applications demanding robust thermal performance and flexible power sequencing.

FAQ

What is the minimum input voltage supported by TPS54821RHLT on the PVIN pin?

The TPS54821RHLT supports a minimum PVIN voltage of 1.6 V, enabling use with low-voltage intermediate distribution buses such as 3.3 V or 2.5 V rails. This split-rail architecture separates power stage input (PVIN) from control circuitry supply (VIN), allowing optimized efficiency in multi-rail systems. The VIN pin still requires 4.5–17 V for internal logic operation. TPS54821RHLT maintains full 8 A output capability across the specified PVIN range when thermal limits are observed.

How does the TPS54821RHLT achieve monotonic start-up into a pre-biased output?

The TPS54821RHLT prevents low-side MOSFET conduction during start-up until the SS/TR pin voltage exceeds 1.4 V, ensuring the output capacitor is not discharged when powered into an already biased rail. This behavior is hard-coded in the device's control logic and requires no external configuration. The SS/TR pin's 2.3 µA charge current sets the ramp rate, and the internal comparator enforces the 1.4 V threshold before enabling low-side sinking. TPS54821RHLT thus guarantees safe hot-swap and power sequencing in complex multi-rail systems.

What is the purpose of the BOOT-PH UVLO threshold in the TPS54821RHLT?

The BOOT-PH UVLO threshold (typ. 2.1 V) in the TPS54821RHLT monitors the bootstrap capacitor voltage relative to the switch node (PH). If BOOT-PH falls below this threshold, the high-side MOSFET is disabled to prevent insufficient gate drive and potential shoot-through. This feature ensures reliable high-side switching across duty cycles and input conditions. TPS54821RHLT can operate at 100% duty cycle only when BOOT-PH remains above 2.1 V, making proper boot capacitor sizing and placement critical for low-VIN or high-duty-cycle applications.

Can the TPS54821RHLT synchronize to an external clock, and how is it configured?

Yes, the TPS54821RHLT synchronizes to an external clock via the RT/CLK pin (Pin 1). When a clean CMOS/TTL clock signal is applied directly to RT/CLK, the internal PLL automatically detects the edge and locks to the external frequency - overriding any RT resistor setting. The device supports synchronization to frequencies within its 200 kHz–1.6 MHz range and aligns switching edges to the falling edge of the external clock. TPS54821RHLT requires no mode-select pins or configuration registers; sync mode activates autonomously upon clock detection.

What thermal management provisions does the TPS54821RHLT require on the PCB?

The TPS54821RHLT requires soldering its exposed thermal pad (Pin 15) to a dedicated PCB copper pour connected to ground, with ≥4 thermal vias (0.010″ diameter) underneath the pad to inner ground planes. TI's recommended layout achieves RθJB = 14.4 °C/W, enabling 8 A continuous operation at 125 °C junction temperature. Insufficient thermal relief causes premature thermal shutdown - especially under high ambient or high-duty-cycle conditions. TPS54821RHLT's thermal hiccup protection disables the device at 160–175 °C and re-enables after 16384 cycles, but sustained operation relies on proper board-level thermal design.