Texas Instruments SN74AHCT257QPWRQ1

Overview

SN74AHCT257QPWRQ1 from Texas Instruments is an AEC-Q100 Grade 1 automotive-qualified quad 2-input data selector/multiplexer with three-state non-inverting outputs, operating from 4.5 V to 5.5 V, delivering 4.3 ns typical propagation delay at 25°C/5V, and supporting shared A/B select and active-low OE control across all four channels for bus-oriented data routing in engine control units and ADAS domain controllers.

For engineers reviewing the SN74AHCT257QPWRQ1 datasheet, SN74AHCT257QPWRQ1 pinout, SN74AHCT257QPWRQ1 application, or SN74AHCT257QPWRQ1 equivalent, key selection criteria include TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V at 5 V), 3-state output drive capability (±8 mA), latch-up immunity (>250 mA), thermal performance in TSSOP-16 (RθJA = 135.9 °C/W), and AEC-Q100 qualification for -40°C to +125°C operation.

Technical Context

The SN74AHCT257QPWRQ1 implements four independent 2:1 multiplexers sharing a common A/B select line and active-low output-enable (OE) input, enabling simultaneous channel selection and tri-state control. Its CMOS architecture with TTL-compatible inputs ensures interoperability with legacy 5 V logic while maintaining low static current (ICC ≤ 40 µA).

Each channel features balanced CMOS three-state outputs capable of sourcing and sinking ±8 mA at VOH ≥ 3.94 V and VOL ≤ 0.36 V under 5 V supply, with switching characteristics specified for 15 pF and 50 pF loads - tPHL/tPLH ≤ 9 ns (15 pF) and ≤ 13.5 ns (50 pF) - ensuring deterministic timing in high-speed digital buses.

Key Specifications

Pinout & Package

SN74AHCT257QPWRQ1 is packaged in a 16-pin TSSOP (PW) with body size 5 mm × 4.4 mm and overall footprint 5 mm × 6.4 mm. The package supports standard surface-mount reflow and is compatible with automated optical inspection (AOI) due to defined lead geometry.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2-input multiplexer applications.

Compared with SN74LV257AQPWRQ1 and MC74VHC257DTG, the SN74AHCT257QPWRQ1 delivers superior timing performance (4.3 ns vs ≥11 ns), guaranteed 5 V operation, and full AEC-Q100 Grade 1 qualification - making it the sole choice for safety-relevant engine and chassis control functions requiring deterministic latency and long-term reliability.

Availability

SN74AHCT257QPWRQ1 is available at Aetrix Electronics and suitable for engine control units, ADAS sensor fusion modules, and body control modules requiring stable component supply, long-lifecycle assurance, and automotive-grade traceability.

Supply support for SN74AHCT257QPWRQ1 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 automotive ICs, with decades of experience in high-reliability automotive electronics design and manufacturing.

The SN74AHCT257QPWRQ1 belongs to TI's automotive logic portfolio, engineered specifically for signal routing in harsh-environment vehicle subsystems where AEC-Q100 compliance, precise timing, and robust ESD/latch-up immunity are mandatory.

FAQ

What is the maximum capacitive load the SN74AHCT257QPWRQ1 can drive while maintaining specified timing?

The SN74AHCT257QPWRQ1 is characterized for 15 pF and 50 pF loads, with switching parameters guaranteed up to 50 pF. Driving larger capacitances increases propagation delay and may violate setup/hold margins; TI recommends limiting total output load to ≤50 pF for full specification compliance. For heavier loads, buffer stages or layout optimization (shorter traces, reduced parallelism) are advised. SN74AHCT257QPWRQ1 datasheet Table 5-6 confirms tPHL/tPLH ≤13.5 ns at CL = 50 pF and TA = –40°C to +125°C.

Does the SN74AHCT257QPWRQ1 support mixed-voltage operation between 3.3 V and 5 V logic domains?

No - the SN74AHCT257QPWRQ1 requires a 4.5 V to 5.5 V VCC supply and is not designed for 3.3 V operation. Its TTL-compatible inputs accept VIH ≥ 2.0 V and VIL ≤ 0.8 V at 5 V, but input thresholds scale with VCC; at lower supplies, noise margins degrade and functionality is not guaranteed. For 3.3 V systems, consider SN74LV257AQPWRQ1 instead. SN74AHCT257QPWRQ1 absolute maximum ratings also prohibit VCC < 4.5 V.

How should unused inputs be terminated on the SN74AHCT257QPWRQ1?

All unused inputs - including A/B, OE, and any unconnected 1A/1B/2A/etc. - must be tied to a valid logic level (VCC or GND) to prevent floating states that cause excessive current draw, oscillation, or undefined outputs. TI recommends 10 kΩ pull-up or pull-down resistors for inputs that may transition later in system operation. Direct connection is acceptable for permanently static inputs. This requirement is explicitly stated in Section 7.3.2 and Figure 8-3 of the SN74AHCT257QPWRQ1 datasheet.

Is the thermal pad on the SN74AHCT257QPWRQ1's WQFN variant required to be connected?

The SN74AHCT257QPWRQ1 in PW (TSSOP-16) package - which matches the "QPWRQ1" suffix - does not have a thermal pad; that feature applies only to the BQB (WQFN) variant. For the TSSOP version, no thermal pad connection is present or needed. Thermal management relies on standard PCB copper pour under pins 8 (GND) and 16 (VCC). RθJA = 135.9 °C/W is specified for the PW package under JEDEC JESD51-7 conditions.

Can multiple SN74AHCT257QPWRQ1 outputs be paralleled to increase drive strength?

Yes - TI explicitly permits paralleling outputs from the same SN74AHCT257QPWRQ1 device when driven by identical inputs, as noted in Section 8.3.3. This configuration doubles current capability (e.g., ±16 mA) while maintaining matched timing. However, outputs from different SN74AHCT257QPWRQ1 devices must never be paralleled due to potential voltage mismatch and shoot-through current. Always ensure shared A/B and OE control across paralleled channels.