Texas Instruments SN74LS377DW

Overview

SN74LS377DW from Texas Instruments is an octal D-type flip-flop with clock enable, implemented in TTL logic, featuring 8 independent edge-triggered storage elements, 10 ns propagation delay (t_PLH/t_PHL), and operation over 0°C to 70°C. It serves as a synchronous data latch in bus interface, address registration, and control signal staging applications within legacy industrial and test equipment.

For engineers reviewing the SN74LS377DW datasheet, SN74LS377DW pinout, SN74LS377DW application, or SN74LS377DW equivalent, key selection criteria include its 20-pin SOIC package, single active-high clock enable input, non-inverting Q outputs, and compatibility with standard LS-TTL voltage thresholds and drive capability.

Technical Context

The SN74LS377DW implements eight identical D-type latches sharing a common clock and a single active-high enable (CLKEN) that gates the clock signal to all flip-flops. Data on the D inputs is transferred to the Q outputs only on the rising edge of the enabled clock, ensuring synchronized parallel data capture.

Its internal architecture uses bipolar Schottky-clamped transistors for speed-power optimization, delivering typical I_OH = –0.4 mA and I_OL = 8 mA output drive at V_CC = 5 V, compatible with standard LS-TTL fanout requirements and direct interfacing to other 74LS-series devices without level translation.

Key Specifications

Pinout & Package

SN74LS377DW is housed in a 20-pin small-outline integrated circuit (SOIC) package with 1.27 mm pitch, 7.5 mm body width, and 2.65 mm maximum height per JEDEC MS-013. Pin 1 is located at the top-left corner with a beveled edge marker.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS377N and SN74LS377NSR, the SN74LS377DW offers identical core functionality in the same SOIC-20 package but with distinct part marking (LS377) and obsolete status-making it suitable only for legacy design continuity or specific inventory reuse, whereas SN74LS377NSR remains actively distributed for new production.

Availability

SN74LS377DW is available at Aetrix Electronics and suitable for industrial bus interface, test equipment address latching, legacy control signal staging, and microprocessor system I/O expansion requiring stable component supply and long-term obsolescence management support.

Supply support for SN74LS377DW 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 solutions with broad industrial, automotive, and communications product portfolios.

The SN74LS377DW belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-cost digital signal registration in commercial-grade systems where speed, power efficiency, and TTL compatibility were primary design constraints.

FAQ

What is the clock enable behavior of the SN74LS377DW?

The SN74LS377DW features a single active-high clock enable (CLKEN) input that gates the CLK signal to all eight internal D-type flip-flops. When CLKEN is LOW, the clock is blocked and no data is latched regardless of CLK transitions; only when CLKEN is HIGH does the rising edge of CLK propagate to update Q outputs. This allows precise control over data capture timing without external logic.

Does the SN74LS377DW support mixed-voltage interfacing?

No, the SN74LS377DW operates strictly at 5 V (4.75–5.25 V) and is designed for standard LS-TTL voltage levels. Its input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) and output swing (V_OH ≥ 2.7 V, V_OL ≤ 0.5 V) are incompatible with 3.3 V or lower logic families without level-shifting circuitry. Direct connection to non-5 V systems risks incorrect logic interpretation or damage.

Can the SN74LS377DW replace the SN74LS373 in a design?

No-the SN74LS377DW is an edge-triggered D-type flip-flop, while the SN74LS373 is an octal transparent latch with enable-controlled pass-through behavior. They differ fundamentally in timing model: SN74LS377DW captures data only on CLK rising edges, whereas SN74LS373 holds data while LE is HIGH and freezes it when LE goes LOW. Substitution would require redesign of clocking and control logic.

What is the maximum clock frequency supported by the SN74LS377DW?

The SN74LS377DW 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 ≤ 10 ns and minimum CLK high/low times of 20 ns each, the practical upper limit is approximately 25 MHz for robust operation, assuming adequate setup/hold margins and clean clock edges.

Is the SN74LS377DW RoHS compliant?

Yes, the SN74LS377DW is RoHS compliant, with lead finish specified as NiPdAu (NIPDAU) and MSL rating Level-1-260°C-UNLIM per JEDEC J-STD-020. This confirms full compliance with EU Directive 2011/65/EU and related restrictions on hazardous substances, verified through TI's official packaging documentation for the DW package variant.