Texas Instruments SNJ54HC377J

Overview

SNJ54HC377J from Texas Instruments is a military-grade octal D-type positive-edge-triggered flip-flop with latched clock enable (CLKEN), operating across –55°C to +125°C. It features 2 V–6 V supply range, 12 ns typical propagation delay at 6 V, ±4 mA output drive, and low 80 µA max ICC. Used in high-reliability buffer/storage register applications within avionics and defense timing subsystems.

For engineers reviewing the SNJ54HC377J datasheet, SNJ54HC377J pinout, SNJ54HC377J application, or SNJ54HC377J equivalent, key selection criteria include its CDIP-20 package, latched CLKEN architecture preventing false clocking, guaranteed operation over extended temperature, and compatibility with legacy HC logic families in radiation-tolerant designs.

Technical Context

The SNJ54HC377J implements eight independent D-type flip-flops sharing a common positive-edge-triggered clock and a latched clock-enable input. Its CLKEN is internally latched to eliminate sensitivity to noise or glitches on the enable line - unlike the 'HC273's asynchronous clear - ensuring deterministic state updates only on valid CLK edges when CLKEN is asserted low.

It operates in standard CMOS logic family voltage thresholds: VIH = 4.2 V (min) and VIL = 1.8 V (max) at VCC = 6 V, with input leakage ≤1 µA and output drive capability of ±4 mA at 5 V. Timing parameters are specified over full military temperature range (–55°C to +125°C), with tpd = 41 ns (max) at VCC = 6 V and TA = 125°C.

Key Specifications

Pinout & Package

SNJ54HC377J is housed in a 20-pin Ceramic Dual In-line Package (CDIP) with 0.300-inch body width, 26.92 mm × 6.92 mm nominal footprint, and through-hole mounting. The package uses tin-lead (SNPB) lead finish and is rated for indefinite reflow (N/A MSL) due to ceramic construction.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal D-type flip-flop applications.

Compared with SN74HC377N and SNJ54HC273J, SNJ54HC377J uniquely combines military temperature range, latched enable robustness, and HC-family compatibility - making it the sole option for new avionics register designs requiring both environmental resilience and noise-immune clock gating.

Availability

SNJ54HC377J is available at Aetrix Electronics and suitable for avionics subsystems, defense electronics, and high-reliability industrial controllers requiring stable component supply across long production lifecycles and extreme environmental conditions.

Supply support for SNJ54HC377J 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 logic solutions, with decades of heritage in military-qualified components.

The SNJ54HC377J belongs to TI's 54HC logic family, designed specifically for high-reliability applications demanding extended temperature operation, radiation tolerance, and proven field performance in mission-critical systems.

FAQ

What is the maximum clock frequency supported by SNJ54HC377J at 6 V and 125°C?

At VCC = 6 V and TA = 125°C, SNJ54HC377J supports a maximum clock frequency of 19 MHz, as specified in the switching characteristics table. This limit accounts for worst-case propagation delay (tpd = 41 ns max) and setup/hold timing margins under full military temperature stress, ensuring deterministic operation in high-temperature avionics enclosures.

Does SNJ54HC377J require external pull-up or pull-down resistors on unused inputs?

Yes, SNJ54HC377J requires all unused inputs-including D, CLK, and CLKEN-to be tied to VCC or GND per TI's SCBA004 application report. Floating inputs can cause excessive ICC, logic contention, or oscillation due to undefined CMOS gate states, especially critical in high-reliability systems where latent failures are unacceptable.

How does the latched CLKEN input in SNJ54HC377J differ from the enable in SN74HC273?

The SNJ54HC377J uses a latched CLKEN that samples and holds the enable state prior to CLK edge arrival, eliminating sensitivity to enable glitches during clock transitions. In contrast, SN74HC273 has no enable - it uses an asynchronous active-low CLR, which resets outputs independently of CLK and cannot gate clocked data flow with the same noise immunity.

Is SNJ54HC377J RoHS compliant?

No, SNJ54HC377J uses a tin-lead (SNPB) lead finish and is not RoHS compliant. It is manufactured per MIL-PRF-38535 requirements for military applications where Pb-based finishes are permitted and preferred for solder joint reliability under thermal cycling and mechanical shock.

Can SNJ54HC377J be used as a direct replacement for SN74HC377 in an existing PCB layout?

Yes, SNJ54HC377J shares identical pinout, electrical interface, and functional behavior with SN74HC377, but uses a CDIP-20 package instead of SOIC/PDIP. Mechanical replacement requires verifying board footprint compatibility - SNJ54HC377J's 26.92 mm × 6.92 mm CDIP matches neither SOIC nor PDIP land patterns, so PCB redesign is needed unless the original layout accommodates CDIP.