onsemi 74ACT16646MTDX

Overview

74ACT16646MTDX from Fairchild Semiconductor is a 16-bit bidirectional registered transceiver with 3-STATE outputs, designed for high-speed bus interface and data multiplexing between A and B buses. It features independent A/B registers, real-time and stored-mode data transfer, DIR-controlled directionality, CPAB/CPBA edge-triggered register loading, and ±24 mA output drive at 5 V.

For engineers reviewing the 74ACT16646MTDX datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional register control timing (tPHL/tPLH ≤ 9.4 ns), 3-STATE enable/disable latency (tPZL/tPLZ ≤ 12.7 ns), TTL-compatible inputs, and TSSOP-56 package compatibility with JEDEC MO-153.

Technical Context

The 74ACT16646MTDX implements dual 8-bit register banks (A0–7 and B0–7) with separate DIR1/DIR2 and G1/G2 controls, enabling byte-level or full 16-bit operation. Data flow direction is determined by DIR inputs, while CPAB and CPBA trigger LOW-to-HIGH clocked register loads-allowing concurrent real-time bus pass-through and register update.

Its 3-STATE outputs are controlled independently per byte via G1/G2, supporting isolation, bus contention avoidance, and multiplexed data routing. The device operates strictly within 4.5 V to 5.5 V supply range and −40°C to +85°C industrial temperature range, with guaranteed AC timing under CL = 50 pF load.

Key Specifications

Pinout & Package

74ACT16646MTDX is housed in a 56-lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153 compliant, 6.1 mm wide, with 0.5 mm lead pitch and exposed thermal pad (not electrically connected). Pin numbering follows standard TSSOP convention, starting at pin 1 (top-left corner, dot-marked).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit registered transceiver applications.

Compared with 74ACT16646MTDX, the 74ACT16245MTD sacrifices register storage and bidirectional control flexibility for lower gate count and cost, while the SN74ALVCH16646GR trades 5 V compatibility and pinout familiarity for speed and power efficiency-making 74ACT16646MTDX the sole choice for industrial 5 V systems needing register-based bus management.

Availability

74ACT16646MTDX is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extenders, and test equipment data mux applications requiring stable component supply, long-lifecycle support, and verified 5 V logic compatibility.

Supply support for 74ACT16646MTDX 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in analog and mixed-signal ICs, acquired by ON Semiconductor in 2016. Its ACT family delivered advanced CMOS performance with TTL compatibility.

The 74ACT16646MTDX belongs to Fairchild's Advanced CMOS (ACT) logic series, engineered for high-speed, low-noise 5 V digital systems where register-controlled bus integrity and timing predictability are critical-especially in industrial control and instrumentation.

FAQ

What is the operating voltage range for the 74ACT16646MTDX?

The 74ACT16646MTDX operates over a supply voltage range of 4.5 V to 5.5 V. This range ensures robust compatibility with standard 5 V TTL and CMOS systems while accommodating typical power rail tolerances in industrial environments. Operation outside this range may cause functional failure or permanent damage, as specified in the Absolute Maximum Ratings table of the original Fairchild datasheet DS500345.

Does the 74ACT16646MTDX support true bidirectional data flow on each pin?

Yes, the 74ACT16646MTDX supports true bidirectional I/O on all A0–A7 and B0–B7 pins. Each pin functions as either input or output depending on DIR and G control states, with no internal direction latching beyond the register stage. Real-time mode allows immediate pass-through, while stored mode routes data from internal A/B registers-enabling flexible protocol implementation without external direction logic.

What is the maximum clock frequency supported by the 74ACT16646MTDX registers?

The 74ACT16646MTDX does not specify a maximum clock frequency; instead, it defines minimum pulse width (tW ≥ 4.0 ns) and setup/hold times (tS ≥ 3.0 ns, tH ≥ 1.5 ns) for CPAB/CPBA inputs. These parameters support reliable register operation up to approximately 100 MHz in well-terminated 50 pF load conditions, as derived from AC Electrical Characteristics in DS500345. System-level timing must account for board trace delays and signal integrity.

Is the 74ACT16646MTDX pin-compatible with the 74ACT16245MTD?

No, the 74ACT16646MTDX is not pin-compatible with the 74ACT16245MTD. Although both use TSSOP-56 packages, their pin assignments differ significantly: the 74ACT16646MTDX includes dedicated CPAB/CPBA and DIR control pins absent in the 74ACT16245MTD, which uses separate OE and DIR lines per direction. PCB layout and firmware control logic must be redesigned for substitution.

What thermal considerations apply to the 74ACT16646MTDX in continuous operation?

The 74ACT16646MTDX has no specified thermal resistance (θJA) in its datasheet, but its TSSOP-56 package (MTD56) features an exposed thermal pad. For continuous operation at full output drive (±24 mA per pin), ambient temperature should remain ≤ +70°C with adequate PCB copper pour under the pad. Power dissipation is dominated by dynamic switching (CPD = 95 pF); derating is recommended above 70°C ambient to maintain reliability within the −40°C to +85°C operating range.