Texas Instruments SN74AHC245QPWRG4Q1

Overview

SN74AHC245QPWRG4Q1 from Texas Instruments is an automotive-qualified octal bus transceiver with 3-state outputs, enabling bidirectional data flow between A and B buses under DIR control and high-impedance isolation via active-low OE. It operates from 2 V to 5.5 V, supports –40°C to +125°C ambient temperature, and delivers ≤10 ns propagation delay at 5 V with 15 pF load.

For engineers reviewing the SN74AHC245QPWRG4Q1 datasheet, SN74AHC245QPWRG4Q1 pinout, SN74AHC245QPWRG4Q1 application, or SN74AHC245QPWRG4Q1 equivalent, key selection factors include AEC-Q100 Grade 1 qualification, balanced CMOS 3-state drive (±8 mA at 5 V), latch-up immunity (>250 mA), and TSSOP-20 wettable-flank package compatibility with automated optical inspection.

Technical Context

The SN74AHC245QPWRG4Q1 implements asynchronous bidirectional bus communication using a single DIR input to select data direction (A→B or B→A) and an active-low OE input to place all eight channels into high-impedance state. Its standard CMOS inputs require fast transitions (<20 ns/V at 5 V) and must be terminated to VCC or GND to prevent oscillation.

It features balanced CMOS 3-state outputs capable of sourcing and sinking up to ±8 mA at 5 V while maintaining VOL ≤0.44 V and VOH ≥3.8 V. The device includes internal clamp diodes on all I/O pins and meets AEC-Q100 HBM Class 2 (±2 kV) and CDM Class C6 (±1 kV) ESD requirements.

Key Specifications

Pinout & Package

Packaged in a 20-pin TSSOP (PW) with wettable flanks for AOI-compatible solder joint inspection; body size 6.5 mm × 4.4 mm, overall footprint 6.5 mm × 6.4 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver applications.

Compared with SN74LVC245AQPWRQ1 and MC74VHC245DTG, the SN74AHC245QPWRG4Q1 uniquely combines full 2–5.5 V operation, AEC-Q100 Grade 1 qualification, and wettable-flank TSSOP packaging-making it the only option qualified for production deployment in powertrain and chassis ECUs requiring long-term reliability and automated assembly verification.

Availability

SN74AHC245QPWRG4Q1 is available at Aetrix Electronics and suitable for automotive body control, ADAS sensor bridging, and EPS motor driver interfacing requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for SN74AHC245QPWRG4Q1 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 and embedded processing technologies, with leadership in automotive-grade logic, power management, and signal chain solutions.

The SN74AHC245QPWRG4Q1 belongs to TI's AHC logic family designed specifically for robust, low-power, high-speed bus interfacing in automotive electronics-emphasizing AEC-Q100 compliance, ESD resilience, and manufacturability in high-reliability SMT lines.

FAQ

What is the maximum capacitive load the SN74AHC245QPWRG4Q1 can drive while maintaining specified timing?

The SN74AHC245QPWRG4Q1 is characterized for loads up to 50 pF in its switching specifications (e.g., tPLH/tPHL). Driving >50 pF increases propagation delay nonlinearly and may violate setup/hold margins in high-speed interfaces. For 15 pF loads at 5 V, typical tPLH is 4 ns; at 50 pF, it rises to 8.5 ns. To maintain timing integrity, keep total net capacitance-including trace, connector, and receiver input-≤50 pF unless derating is applied per application curves in the SN74AHC245QPWRG4Q1 datasheet.

How should the OE pin be handled during power-up to ensure bus isolation for the SN74AHC245QPWRG4Q1?

To guarantee high-impedance state at power-up, OE must be held HIGH (inactive) until VCC stabilizes. TI recommends tying OE to VCC through a pullup resistor; minimum value depends on the current-sinking capability of the driving circuit. For most microcontrollers, a 10 kΩ resistor suffices. If OE is driven actively, ensure its control signal asserts HIGH before VCC reaches 1.5 V-verified via power sequencing analysis. Failure to do so risks bus contention or backfeeding between A and B sides during brown-out conditions.

Does the SN74AHC245QPWRG4Q1 support 5 V logic levels when powered from 3.3 V?

No. The SN74AHC245QPWRG4Q1 is not 5 V tolerant when VCC = 3.3 V. Its absolute maximum input voltage is VCC + 0.5 V, meaning inputs must stay within 0–3.8 V. Applying 5 V signals to A/B or DIR/OE pins at 3.3 V VCC violates absolute maximum ratings and risks permanent damage. For mixed-voltage interfacing, use a level-shifter stage or select the SN74LVC245AQPWRQ1 (5 V tolerant inputs) if operating at 3.3 V VCC with 5 V upstream signals.

What is the purpose of the thermal pad in the RKS (VQFN) package variant, and does the SN74AHC245QPWRG4Q1 include it?

The thermal pad in the RKS (VQFN) package provides enhanced heat dissipation from the die to the PCB, lowering junction-to-board thermal resistance (RθJB = 73.1°C/W). However, the SN74AHC245QPWRG4Q1 uses the PW (TSSOP-20) package, which has no thermal pad. Its RθJA is 122.3°C/W-higher than RKS-but sufficient for typical automotive logic applications drawing <10 mW. No thermal pad soldering or PCB stencil design is required for SN74AHC245QPWRG4Q1.

Can unused input pins on the SN74AHC245QPWRG4Q1 be left floating?

No. All unused inputs-including DIR, OE, and any unconnected A/B pins-must be terminated to either VCC or GND. Floating CMOS inputs cause excessive current draw, logic instability, and potential device latch-up due to intermediate voltage states. TI specifies a 10 kΩ pullup or pulldown resistor as standard practice. Leaving inputs unconnected violates the Recommended Operating Conditions and voids AEC-Q100 qualification validity in production audits.