STMicroelectronics ST2129QTR

Overview

ST2129QTR from STMicroelectronics is a 2-bit bidirectional dual-supply level translator without direction control pin, designed for voltage translation between 1.65–3.6 V (VL) and 1.65–5.5 V (VCC) domains. It supports up to 84 Mbps data rate at VL = 1.8 V / VCC = 3.3 V, features power-down mode with high-impedance I/Os when VCC is off, and uses totem-pole output drivers. It is used in mobile phone baseband-to-peripheral interfaces requiring seamless low-voltage logic interoperability.

For engineers reviewing the ST2129QTR datasheet, ST2129QTR pinout, ST2129QTR application, or ST2129QTR equivalent, key selection criteria include bidirectional operation without direction pin, 5.5 V-tolerant OE input, ±2 kV HBM ESD rating, QFN10 (1.8 × 1.4 mm) footprint, and guaranteed AC performance across VL/VCC combinations.

Technical Context

The ST2129 employs an auto-sensing architecture with weak pull-up/pull-down networks and one-shot transistors that activate only during signal transitions-enabling true bidirectional level shifting without external direction control. Its I/Os are internally biased to maintain state via 4 kΩ resistive hold paths after transition completion.

It supports partial power-down: when VCC = 0 V or floating, all I/Os enter high-impedance regardless of OE state; OE itself is 5.5 V tolerant and referenced to VL. Driver requirements mandate ≥1 mA sourcing/sinking capability on both sides to reliably charge/discharge the 4 kΩ buffer node.

Key Specifications

Pinout & Package

ST2129QTR is housed in a RoHS-compliant, ECOPACK®-qualified QFN10 package measuring 1.8 mm × 1.4 mm × 0.5 mm with 0.4 mm pitch and exposed thermal pad (pin 6 = GND). The package supports automated optical inspection and provides low-inductance grounding via the bottom thermal pad.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional level translation applications.

Compared with TXS0102 and PCA9306, ST2129QTR uniquely combines VCC-off automatic high-Z, 5.5 V-tolerant OE, and low-quiescent-current operation - making it the only option qualified for battery-backed mobile and hot-pluggable embedded systems requiring fail-safe isolation.

Availability

ST2129QTR is available at Aetrix Electronics and suitable for mobile device integration, sensor hub interconnects, and industrial I/O expansion requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ST2129QTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.

The ST2129 belongs to ST's level translation portfolio, engineered specifically for ultra-compact, low-power, and directionless voltage bridging in portable and multi-rail embedded systems - emphasizing reliability under dynamic power sequencing.

FAQ

Can ST2129QTR translate between 1.2 V and 3.3 V logic domains?

No. ST2129QTR's VL supply range is strictly 1.65 V to 3.6 V per datasheet Table 5. A 1.2 V source falls below the minimum VL rating and risks undefined logic thresholds, increased leakage, and potential damage due to violation of absolute maximum ratings (VI/OVL min = –0.3 V, but functional operation is not characterized below 1.65 V).

What happens to I/O states when OE is pulled high but VCC is disconnected?

All I/Os automatically enter high-impedance state regardless of OE logic level when VCC is 0 V or floating - this is a hardware-enforced power-down feature confirmed in Section 3.3 and Table 3 truth table. OE remains functional only when VCC is within operating range (1.65–5.5 V).

Is the exposed thermal pad on QFN10 required to be soldered to PCB ground?

Yes. Per Figure 8 and Table 13, pin 6 (GND) connects directly to the exposed thermal pad. ST recommends soldering the pad to a solid GND plane using ≥4 thermal vias (0.3 mm diameter) to ensure thermal dissipation, mechanical stability, and optimal EMI performance - omission degrades reliability and AC timing margins.

Does ST2129QTR support I²C bus speeds up to 400 kHz or 1 MHz?

Yes. With CL = 15 pF and proper pull-up sizing (≤2.2 kΩ for 3.3 V), ST2129QTR achieves tR/tF < 2.6 ns (Table 8–10), well below I²C Fast-mode Plus (1 MHz) requirements. Its bidirectional architecture preserves open-drain behavior, and propagation delays (<4.5 ns) introduce negligible skew in standard and fast-mode I²C implementations.