Texas Instruments TPS22981RGPT

Overview

TPS22981 from Texas Instruments is a dual-input, resistor-programmable power mux IC for Thunderbolt™/Thunderbolt II™ systems, supporting 3.3-V (3–3.6 V) and high-voltage (4.5–19.8 V) supply selection with make-before-break switching, adjustable current limiting (100 mA to 1.5 A per path), reverse current blocking, and thermal shutdown. It enables seamless voltage-mode transitions in notebook and desktop host ports.

For engineers reviewing the TPS22981 datasheet, TPS22981 pinout, TPS22981 application, or TPS22981 equivalent, key selection considerations include VHV/V3P3 transition timing (e.g., 23-ms VHV-to-3.3-V ramp), independent S0/S3 mode current limit control, UVLO thresholds (VHVUVLO = 4.0–4.3 V, V3P3UVLO = 2.25–2.5 V), and fault reporting via open-drain FAULTZ.

Technical Context

The TPS22981 implements two independent NMOS power switches - one for VHV (4.5–19.8 V) and one for V3P3 (3–3.6 V) - each with externally set current limits via ISET pins and RSET resistors. Switching logic supports EN/HV_EN-controlled state selection and ENHVU-gated dual-UVLO enable, ensuring both supplies must meet threshold before high-voltage operation.

Transition behavior is tightly controlled: during VHV→V3P3 switchover, the device breaks VHV, discharges OUT to ~3.3 V using IDIS = 5–10 mA, then enables V3P3; during V3P3→VHV, it enables both paths until reverse current (≥10 mA) is detected on V3P3, then disables the low-voltage switch. Thermal shutdown activates at TJ = 110–130 °C with 10 °C hysteresis.

Key Specifications

Pinout & Package

VQFN-20 (RGP) package, 4.0 mm × 4.0 mm × 1.0 mm, with exposed thermal pad (EP) requiring connection to GND for thermal management and electrical reference.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power mux applications.

Compared with TPS22975YFPR and TPS259472LAR, the TPS22981 uniquely integrates dual-supply selection, Thunderbolt-optimized transition sequencing, V3P3 bypass output, and S0-gated dual VHV current limits - making it irreplaceable for compliant Thunderbolt host port designs.

Availability

TPS22981 is available at Aetrix Electronics and suitable for notebook computers, desktop Thunderbolt add-in cards, and industrial docking stations requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for TPS22981 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 specializing in analog, embedded processing, and connectivity solutions, with leadership in power management and interface ICs for computing and industrial markets.

The TPS22981 belongs to TI's Thunderbolt™-optimized power mux product line, designed specifically to meet the stringent voltage-transition, current-limiting, and fault-reporting requirements of Mini DisplayPort-based host interfaces.

FAQ

What is the primary function of the TPS22981 in a Thunderbolt system?

The TPS22981 serves as a dual-input power multiplexer that enables seamless, droop-free transitions between 3.3-V (V3P3) and high-voltage (VHV: 4.5–19.8 V) supply rails in Thunderbolt host ports. It implements make-before-break switching from V3P3 to VHV and discharge-before-make from VHV to V3P3, ensuring continuous power delivery during protocol negotiation. The TPS22981 also provides resistor-programmable current limiting, UVLO protection, and fault reporting - all critical for Thunderbolt II compliance.

How does the TPS22981 handle transitions between VHV and V3P3 supply rails?

The TPS22981 uses distinct, controlled sequences: during V3P3→VHV transition, it enables both paths simultaneously until reverse current ≥10 mA is detected on the V3P3 switch, then disables V3P3. During VHV→V3P3 transition, it first disables VHV, actively discharges OUT to ~3.3 V using a 5–10 mA internal pulldown (IDIS), then enables V3P3. This prevents brownout and shoot-through. Measured delays include T3P3OFF = 6 ms and TVHV-3.3V = 23 ms (10% to >90%).

Can the TPS22981 current limits be adjusted, and how?

Yes, the TPS22981 supports three independently adjustable current limits: V3P3 (via ISET_V3P3/RSET_V3P3), VHV in S0 mode (via ISET_S0/RSET_S0), and VHV in S3 mode (via ISET_S3/RSET_S3). Each uses a resistor from the respective ISET pin to GND. Using Equation 1 from the datasheet, a 26.7–402-kΩ resistor sets limits from 100 mA to 1.5 A. For example, RSET_V3P3 = 80.6 kΩ yields ILIM3P3 ≈ 496 mA typical. The TPS22981 also enforces hard limits (ILIM3P3MAX = 1.8–3.1 A) if an ISET pin is shorted.

What is the role of the ENHVU pin on the TPS22981?

The ENHVU pin determines whether the TPS22981 requires only V3P3 UVLO clearance (ENHVU = low) or both V3P3 and VHV UVLO clearance (ENHVU = high) before enabling. When ENHVU = high, the device will not activate unless both supplies exceed their respective UVLO thresholds (V3P3UVLO = 2.25–2.5 V, VHVUVLO = 4.0–4.3 V), preventing partial enablement during incomplete power-up. This dual-UVLO gating is essential for Thunderbolt systems where VHV may be absent during initial enumeration.

Does the TPS22981 provide reverse current protection, and how is it implemented?

Yes, the TPS22981 provides bidirectional reverse current protection. The V3P3 switch blocks reverse current ≥10 mA (IREV3P3) and responds within 100 µs (TV3P3RC). The VHV switch inherently blocks reverse current when disabled due to its NMOS topology. Additionally, during VHV→V3P3 transitions, the TPS22981 actively discharges OUT to ~3.3 V before enabling V3P3, eliminating risk of backfeed from loaded outputs. This meets Thunderbolt's strict safety requirements for cable hot-plug scenarios.