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Home > Products > Integrated Circuits (ICs) > Logic > Flip Flops

Texas Instruments SN74LS377NE4

Name: SN74LS377NE4
Brand: Texas Instruments
SKU: SN74LS377NE4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS377NE4

Manufacturer:: Texas Instruments

Category:: Flip Flops

Package:: 20-DIP (0.300", 7.62mm)

Datasheet:: SN74LS377NE4.pdf

Description:: SN74LS377 OCTAL D-TYPE FLIP-FLOP

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Product details

Overview

SN74LS377NE4 from Texas Instruments is an octal D-type flip-flop with common clock enable, designed for synchronous data latching in TTL-level digital systems. It features 8 independent edge-triggered storage elements, a single active-high clock enable (CLKEN), and non-inverted Q outputs. Typical use includes address/data register staging in microprocessor bus interfaces operating at ≤30 MHz.

For engineers reviewing the SN74LS377NE4 datasheet, SN74LS377NE4 pinout, SN74LS377NE4 application, or SN74LS377NE4 equivalent, key selection criteria include its 20-pin PDIP package, 0°C to 70°C commercial temperature range, TTL-compatible input thresholds, and guaranteed propagation delay of 25 ns max (t_PLH/t_PHL) under standard load conditions.

Technical Context

The SN74LS377NE4 implements eight identical D-type latches synchronized to the rising edge of the clock signal when CLKEN is high. Its internal structure uses bipolar TTL circuitry with Schottky-clamped transistors to limit saturation and reduce propagation delay.

All eight flip-flops share one clock input (CP), one clock enable (CLKEN), and one master reset (MR) input - MR is asynchronous, active-low, and clears all Q outputs to logic low regardless of clock state.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	74LS (Low-power Schottky TTL) - ensures compatibility with legacy TTL systems and predictable noise margins.
Function	Octal D-type positive-edge-triggered flip-flop with common clock enable and asynchronous master reset.
Propagation Delay	25 ns max (t_PLH/t_PHL, V_CC = 5 V, R_L = 2 kΩ, C_L = 15 pF) - defines maximum clock-to-output timing for synchronous bus registration.
Maximum Clock Frequency	30 MHz typical - sets upper bound for reliable register operation in buffered control/data paths.
Supply Voltage	4.75 V to 5.25 V - requires stable +5 V rail; operation outside this range risks metastability or output invalidation.
Input Thresholds	V_IL ≤ 0.8 V, V_IH ≥ 2.0 V - ensures robust interfacing with standard TTL and LSTTL outputs without level shifting.
Output Drive	I_OL = 8 mA, I_OH = –0.4 mA - supports direct fan-out to up to 10 standard TTL loads per output.

Pinout & Package

SN74LS377NE4 is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is marked by a notch or dot; pin numbering follows counter-clockwise convention from top view.

Pin/Terminal	Circuit Role	Design Meaning
1 (CLKEN)	Clock Enable Input	Active-high control: only allows clock transitions to affect outputs when high; enables synchronous gating of register updates.
2–9 (D1–D8)	Data Inputs	Independent parallel data inputs for each of the eight flip-flops; sampled on rising clock edge when CLKEN = HIGH.
10 (GND)	Ground Reference	Primary return path for all internal current sinks and logic reference; must be low-impedance connection.
11–18 (Q1–Q8)	True Outputs	Non-inverted registered outputs; retain state between clock edges; drive TTL-compatible loads directly.
19 (CP)	Clock Input	Rising-edge-triggered global clock; all eight flip-flops update simultaneously on active transition if CLKEN is asserted.
20 (MR)	Master Reset	Asynchronous active-low reset: forces all Q outputs LOW immediately, overriding clock and enable states.
20 (V_CC)	Power Supply	+5 V supply pin; decoupling capacitor (0.1 µF ceramic) required within 1 cm of this pin for noise immunity.

Key Features

Feature	Design Value
Edge-triggered storage	Positive-edge clocking ensures deterministic sampling of D inputs, eliminating race conditions in synchronous pipelines.
Common clock enable	Single CLKEN line simplifies control logic for enabling/disabling register updates across all eight bits without additional gating.
Asynchronous master reset	MR input provides immediate, clock-independent initialization of all outputs - critical for system power-up or error recovery sequences.
TTL-compatible I/O	Full 74LS voltage/current specifications guarantee interoperability with legacy microprocessor buses (e.g., Z80, 8080, 6800) and peripheral ICs.
20-pin PDIP packaging	Standard through-hole footprint supports prototyping, repair, and industrial control applications where reflow soldering is not preferred.

Applications

Microprocessor Address Latch	Parallel Data Capture Interface
Use Scenario: Holding 8-bit address segments during multiplexed bus cycles in 8-bit CPU systems (e.g., Z80-based controllers). IC Role / Device Role / Timing Role: Acts as a transparent latch for lower-address byte; captures and holds A0–A7 while AD0–AD7 are shared with data. Use Value: Eliminates need for external gating logic by using CLKEN to align capture with MREQ and RD/WR strobes, reducing board space and timing uncertainty.	Use Scenario: Capturing parallel sensor or ADC output data into a microcontroller's memory-mapped I/O space. IC Role / Device Role / Timing Role: Synchronizes asynchronous 8-bit data streams to the system clock domain before CPU read access. Use Value: Provides setup/hold time margin via edge-triggered sampling, preventing metastability when interfacing slow analog front-ends to fast digital logic.
Bus Isolation Register	Digital Control Signal Staging
Use Scenario: Isolating two bidirectional data buses operating at different speeds or voltage domains in industrial PLC backplanes. IC Role / Device Role / Timing Role: Functions as a unidirectional buffer register; CLKEN gates updates to prevent spurious writes during bus arbitration. Use Value: Enables clean handoff between bus masters by holding stable data until both source and destination are ready - avoids contention-induced glitches.	Use Scenario: Staging control bits for stepper motor drivers, relay banks, or display segment drivers in embedded motion-control systems. IC Role / Device Role / Timing Role: Stores command bits (e.g., direction, enable, step pulse) until next clock cycle, decoupling software execution from hardware timing. Use Value: Allows CPU to write full 8-bit control words in one instruction, then release bus while hardware executes timed sequences - improves real-time determinism.

Microprocessor Address Latch

Parallel Data Capture Interface

Use Scenario: Holding 8-bit address segments during multiplexed bus cycles in 8-bit CPU systems (e.g., Z80-based controllers).

IC Role / Device Role / Timing Role: Acts as a transparent latch for lower-address byte; captures and holds A0–A7 while AD0–AD7 are shared with data.

Use Value: Eliminates need for external gating logic by using CLKEN to align capture with MREQ and RD/WR strobes, reducing board space and timing uncertainty.

Use Scenario: Capturing parallel sensor or ADC output data into a microcontroller's memory-mapped I/O space.

IC Role / Device Role / Timing Role: Synchronizes asynchronous 8-bit data streams to the system clock domain before CPU read access.

Use Value: Provides setup/hold time margin via edge-triggered sampling, preventing metastability when interfacing slow analog front-ends to fast digital logic.

Bus Isolation Register

Digital Control Signal Staging

Use Scenario: Isolating two bidirectional data buses operating at different speeds or voltage domains in industrial PLC backplanes.

IC Role / Device Role / Timing Role: Functions as a unidirectional buffer register; CLKEN gates updates to prevent spurious writes during bus arbitration.

Use Value: Enables clean handoff between bus masters by holding stable data until both source and destination are ready - avoids contention-induced glitches.

Use Scenario: Staging control bits for stepper motor drivers, relay banks, or display segment drivers in embedded motion-control systems.

IC Role / Device Role / Timing Role: Stores command bits (e.g., direction, enable, step pulse) until next clock cycle, decoupling software execution from hardware timing.

Use Value: Allows CPU to write full 8-bit control words in one instruction, then release bus while hardware executes timed sequences - improves real-time determinism.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS373N	Octal transparent latch (level-sensitive), no clock edge triggering; uses G and OE pins instead of CP/CLKEN.	Suitable for address latching where data must remain transparent while enable is active, not for edge-synchronized storage.	Select SN74LS373N only when level-sensitive gating is required; SN74LS377NE4 is preferred for clock-domain synchronization.
SN74LS374N	Octal D-type flip-flop with identical pinout and function but separate clock enable per bit (not common); higher drive strength (I_OL = 24 mA).	Better suited for driving heavier loads or multiple downstream devices; less efficient for globally gated updates.	Choose SN74LS374N when per-bit enable control or higher sink current is needed; SN74LS377NE4 offers simpler global control for uniform updates.

Compared with SN74LS373N and SN74LS374N, the SN74LS377NE4 uniquely balances global clock enable simplicity with edge-triggered reliability - making it optimal for bus register applications requiring deterministic, single-cycle updates without per-bit complexity or transparency-related timing hazards.

Availability

SN74LS377NE4 is available at Aetrix Electronics and suitable for industrial control panels, legacy microprocessor upgrades, and educational electronics labs requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS377NE4 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, automotive, and aerospace qualification.

The SN74LS377NE4 belongs to TI's legacy 74LS logic family, engineered for backward compatibility with 1970s–1990s TTL-based digital systems and maintained for long-lifecycle industrial and defense applications.

FAQ

What is the function of the MR pin on the SN74LS377NE4?

The MR (Master Reset) pin on the SN74LS377NE4 is an asynchronous, active-low input that forces all eight Q outputs to logic LOW immediately, regardless of clock or enable state. This function is essential for system initialization, fault recovery, or forced state clearing in the SN74LS377NE4 - and operates independently of the clock edge or CLKEN status.

Can SN74LS377NE4 operate with a 3.3 V supply?

No, the SN74LS377NE4 is specified only for 4.75 V to 5.25 V operation. Applying 3.3 V will result in undefined logic levels, excessive propagation delay, and potential output failure. For 3.3 V systems, consider modern alternatives like SN74LVC374A, not the SN74LS377NE4.

Is SN74LS377NE4 pin-compatible with SN74LS374N?

No, SN74LS377NE4 and SN74LS374N have different pinouts: SN74LS377NE4 places CLKEN on pin 1 and MR on pin 20, whereas SN74LS374N uses pin 1 for OE and pin 11 for MR. Direct substitution would require PCB redesign - the SN74LS377NE4 is not a drop-in replacement for SN74LS374N.

What is the maximum fan-out capability of SN74LS377NE4 outputs?

Each Q output of the SN74LS377NE4 can drive up to 10 standard TTL loads (I_OL = 8 mA, I_OH = –0.4 mA). This fan-out rating assumes standard 74LS input characteristics; exceeding it may cause timing violations or logic errors in the SN74LS377NE4-driven stage.

Does SN74LS377NE4 support hot insertion or live swapping?

No, SN74LS377NE4 is not designed for hot insertion. Its bipolar TTL architecture lacks bus-hold or I_OFF protection; inserting or removing the SN74LS377NE4 while powered risks latch-up, supply rail disturbance, or damage to adjacent components due to uncontrolled current paths.

SN74LS377NE4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 20-DIP (0.300", 7.62mm)

Packaging:: Bulk

Product Status:: Active

Function:: Standard

Type:: D-Type

Output Type:: Non-Inverted

Number of Elements:: 1

Number of Bits per Element:: 8

Clock Frequency:: 40 MHz

Max Propagation Delay @ V, Max CL:: 27ns @ 5V, 15pF

Trigger Type:: Positive Edge

Current - Output High, Low:: 400µA, 8mA

Voltage - Supply:: 4.75V ~ 5.25V

Current - Quiescent (Iq):: 28 mA

Input Capacitance:: -

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 20-PDIP

SN74LS377NE4 FAQ

1.How can I place an order for SN74LS377NE4 through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS377NE4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74LS377NE4 reliable?

The price and inventory of SN74LS377NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS377NE4 is usually 5 days.

3.What payment methods are accepted for SN74LS377NE4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS377NE4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS377NE4?

SN74LS377NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS377NE4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74LS377NE4?

For technical support, including SN74LS377NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS377NE4 requirements.

6.How does Aetrix verify that SN74LS377NE4 is sourced from the original manufacturer or authorized distributors?

All SN74LS377NE4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74LS377NE4 meets industry standards.

7.What is the process for return or replacement of SN74LS377NE4?

All SN74LS377NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS377NE4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74LS377NE4 part is unused and in its original packaging.

Return procedure for SN74LS377NE4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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