Texas Instruments 85506012A

Overview

85506012A from Texas Instruments is a military-grade octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous data transfer between A and B buses in high-reliability systems. It operates from 4.5 V to 5.5 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 14 ns (CL = 50 pF), and supports operation from –55 °C to +125 °C - used in avionics backplanes and radiation-tolerant control interfaces.

For engineers reviewing the 85506012A datasheet, 85506012A pinout, 85506012A application, or 85506012A equivalent, this page provides verified functional modes, thermal metrics for LCCC-20 packaging, TTL-compatible input thresholds, isolation behavior under OE high, and direction-controlled data flow between dual 8-bit buses.

Technical Context

The 85506012A implements a standard '245 logic function with active-low output enable (OE) and unidirectional direction control (DIR): DIR = high enables A→B transfer; DIR = low enables B→A transfer; OE = high places all I/Os in high-impedance state. Its CMOS HCT architecture ensures TTL-voltage compatibility while maintaining low static current (≤80 µA).

It features balanced propagation delay across all eight channels, supports up to 15 LSTTL loads per output, and uses center-aligned VCC/GND pins in its 20-pin LCCC package to minimize switching noise coupling. Absolute maximum ratings include 7 V supply voltage and ±20 mA clamp current, with ESD tolerance of ±1500 V (HBM).

Key Specifications

Pinout & Package

85506012A is housed in a 20-pin Ceramic Leadless Chip Carrier (LCCC, FK package), body size 8.89 mm × 8.89 mm, with solder-sealed ceramic construction rated for hermetic reliability and thermal stability in harsh environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN54HCT245J, 85506012A offers superior thermal resistance and hermetic reliability; compared with JM38510/65553BRA, it shares identical qualification but differs in lot-level documentation scope and supply chain origin - both alternatives require no schematic or layout changes.

Availability

85506012A is available at Aetrix Electronics and suitable for avionics data bus interface, rad-hard motor control module, nuclear plant I/O subsystem, and tactical radio baseband interface requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for 85506012A 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 high-reliability logic solutions for aerospace, defense, and industrial markets.

The SNx4HCT245 product line delivers radiation-tolerant, temperature-extended bus transceivers engineered for deterministic bidirectional data transfer in safety-critical systems where signal integrity and long-term reliability are non-negotiable.

FAQ

What is the operating temperature range of the 85506012A?

The 85506012A is specified for operation from –55 °C to +125 °C, meeting MIL-STD-883 requirements for extended temperature performance in aerospace and defense platforms. This range is validated across all electrical parameters including propagation delay, output drive, and input thresholds - no derating is required within these limits. The LCCC package contributes to thermal stability via low junction-to-board resistance (RθJB = 36.1 °C/W). 85506012A maintains full functionality across this range without external thermal management.

Does the 85506012A support TTL-level inputs?

Yes, the 85506012A features TTL-voltage compatible inputs with VIH ≥ 2.0 V and VIL ≤ 0.8 V over the full 4.5 V to 5.5 V supply range, ensuring direct interfacing with legacy 5 V TTL, LS-TTL, and CMOS logic without level-shifting circuitry. Input current remains ≤ ±100 nA at 25 °C, minimizing loading on upstream drivers. This compatibility is maintained across the entire operating temperature range. 85506012A thus simplifies integration into mixed-technology systems where both HCT and older logic families coexist.

How does the direction control (DIR) pin function in the 85506012A?

The DIR pin on the 85506012A selects data flow direction: logic high enables transmission from Port A to Port B; logic low enables transmission from Port B to Port A. This control is asynchronous and independent of OE state - when OE is high, DIR has no effect as all I/Os are in high-impedance mode. DIR must be stable before data transfer begins to avoid bus contention. 85506012A's DIR input is TTL-compatible and draws ≤100 nA, allowing direct connection to microcontroller GPIOs. No external pull-up/down is required if driven actively.

What is the maximum capacitive load the 85506012A can drive reliably?

The 85506012A is characterized for CL = 50 pF and CL = 150 pF loads, with propagation delay increasing from 14 ns (typical, 5.5 V) to 18 ns (typical, 5.5 V) as load rises. It can reliably drive up to 15 LSTTL loads (≈450 pF total) per output, though timing margins shrink above 100 pF. Output current is limited to ±35 mA per pin and ±70 mA total, so trace capacitance plus load must stay within safe current limits. For 85506012A, maintaining CL ≤ 100 pF ensures <1% duty-cycle distortion at 25 MHz operation.

Is the 85506012A pin-compatible with other SNx4HCT245 variants?

Yes, the 85506012A shares identical 20-pin LCCC (FK) pinout and signal mapping with all SN54HCT245 LCCC variants, including JM38510/65553BRA and SNJ54HCT245FK. Pin 1 is DIR, pins 2–9 are A1–A8, pin 10 is GND, pins 11–18 are B8–B1 (reversed order), pin 19 is OE, and pin 20 is VCC - matching the functional diagram in TI's SCLS020H datasheet. This allows direct substitution within existing LCCC-20 footprints without layout modification. 85506012A maintains full electrical and timing equivalence across this pin-compatible family.