Texas Instruments SN74LS377NG4

Overview

SN74LS377NG4 from Texas Instruments is an octal D-type flip-flop with clock enable, designed for synchronous data latching in TTL-level digital systems. It features 8 independent edge-triggered storage elements, a common clock input, and a single active-high enable control. Typical applications include address/data register staging in microprocessor bus interfaces and parallel I/O expansion.

For engineers reviewing the SN74LS377NG4 datasheet, SN74LS377NG4 pinout, SN74LS377NG4 application, or SN74LS377NG4 equivalent, key selection considerations include its 20-pin PDIP package, 70°C operating temperature range, TTL-compatible input thresholds, 15 ns typical propagation delay, and compatibility with legacy 74LS logic families.

Technical Context

The SN74LS377NG4 implements eight positive-edge-triggered D-type flip-flops sharing a common clock (CLK) and an active-high enable (G). When G is high, data present at each D input transfers to the corresponding Q output on the rising edge of CLK; when G is low, all outputs hold their previous state regardless of CLK transitions.

It operates strictly within the standard 74LS TTL electrical specification: V_CC = 5 V ±5%, input high voltage ≥2.0 V, input low voltage ≤0.8 V, output high current ≥0.4 mA, and output low current ≤8 mA. No internal reset or preset functionality is provided.

Key Specifications

Pinout & Package

SN74LS377NG4 is supplied in a 20-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin 1 is located at the left end of the top row, identified by a notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS373N and SN74LS374N, the SN74LS377NG4 uniquely combines edge-triggered storage with a global enable-offering simpler control logic for pure register staging without bus contention management or transparency modes.

Availability

SN74LS377NG4 is available at Aetrix Electronics and suitable for industrial control systems, legacy computer restoration projects, and educational electronics labs requiring stable component supply and long-term obsolescence support.

Supply support for SN74LS377NG4 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial and automotive qualification.

The SN74LS377NG4 belongs to TI's legacy 74LS logic family, engineered for robust, low-power TTL-compatible digital interfacing in cost-sensitive and reliability-critical applications from the 1970s onward.

FAQ

What is the function of the G (enable) pin on the SN74LS377NG4?

The G pin on the SN74LS377NG4 is an active-high enable input that controls whether the device responds to the clock signal. When G is low, all eight flip-flops hold their current Q outputs regardless of CLK activity; when G is high, data at D0–D7 transfers to Q0–Q7 on each rising CLK edge. This allows precise gating of register updates without modifying the clock tree - a key feature distinguishing SN74LS377NG4 from basic D-flip-flop variants.

Does the SN74LS377NG4 support three-state outputs?

No, the SN74LS377NG4 does not support three-state outputs. Its Q0–Q7 outputs are push-pull TTL drivers with fixed high/low states only. Unlike the pin-compatible SN74LS374N, which includes an output enable (OE) pin for bus sharing, SN74LS377NG4 requires external bus buffers or discrete isolation if multiple devices drive a common data line. This design simplifies control logic but limits direct use in bidirectional bus architectures.

What is the maximum clock frequency supported by the SN74LS377NG4?

The SN74LS377NG4 does not specify a maximum clock frequency in its datasheet; instead, timing is defined by minimum pulse widths and propagation delays. With t_PLH/t_PHL ≤15 ns and minimum CLK high/low times of 20 ns each, the practical upper limit is approximately 20 MHz under ideal conditions. However, system-level timing margins, trace routing, and load capacitance typically constrain reliable operation to ≤10 MHz in real-world PCB implementations using SN74LS377NG4.

Can the SN74LS377NG4 be used in place of the SN74LS374N?

The SN74LS377NG4 and SN74LS374N share identical pinouts, supply requirements, and core flip-flop functionality, but differ critically in output control: SN74LS374N includes an OE pin for three-state outputs, while SN74LS377NG4 has no tri-state capability. Substitution is electrically safe only if the target circuit does not rely on bus sharing or high-impedance states - otherwise, SN74LS374N remains the correct choice for bidirectional data paths.

Is the SN74LS377NG4 RoHS compliant?

Yes, the SN74LS377NG4 is RoHS compliant, featuring lead-free NiPdAu (NIPDAU) terminal finish per TI's official packaging documentation. It meets EU Directive 2011/65/EU requirements and carries the "G4" suffix indicating green (halogen-free, RoHS-compliant) packaging. This compliance applies to all currently active PDIP (N) variants including SN74LS377N, SN74LS377NE4, and SN74LS377NG4.