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

Texas Instruments SN74AS821ANT

Name: SN74AS821ANT
Brand: Texas Instruments
SKU: SN74AS821ANT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74AS821ANT

Manufacturer:: Texas Instruments

Category:: Flip Flops

Package:: 24-DIP (0.300", 7.62mm)

Datasheet:: SN74AS821ANT.pdf

Description:: IC D-TYPE POS TRG SNGL 24DIP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74AS821ANT from Texas Instruments is a dual 10-bit D-type flip-flop with common clock and clear, designed for high-speed synchronous data latching in bus-interface and register applications. It operates at 5 V, supports 100 MHz maximum clock frequency, features TTL-compatible inputs, and delivers 20 ns typical propagation delay (t_PLH/t_PHL). It is used in industrial control backplanes and legacy data acquisition systems.

For engineers reviewing the SN74AS821ANT datasheet, SN74AS821ANT pinout, SN74AS821ANT application, or SN74AS821ANT equivalent, key selection factors include its dual 10-bit latch structure, 5-V TTL-level timing compatibility, guaranteed 20 mA output drive, and availability in plastic DIP-24 package with through-hole mounting.

Technical Context

This device integrates two independent 10-bit edge-triggered D-type flip-flops sharing one master clock (CLK) and one asynchronous clear (CLR) input. Each 10-bit section has separate true and complement outputs (Q and Q̅), enabling direct bus driving without external inverters.

It uses bipolar Schottky TTL technology, delivering fast switching with guaranteed fan-out of 10 LS-TTL loads per output and immunity to input noise spikes down to 0.5 V. The device requires no external pull-ups or level shifters when interfacing with standard 5-V TTL logic families.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	AS (Advanced Schottky) TTL - enables 100 MHz operation with low power-delay product
Supply Voltage	5 V ±5% - compatible with standard TTL power rails; no regulation required
Max Clock Frequency	100 MHz - supports high-throughput data capture in parallel bus architectures
Propagation Delay	20 ns (typ) - ensures tight timing margins in synchronous register chains
Output Drive	20 mA (I_OH/I_OL) - directly drives 10 LS-TTL loads without buffering
Input Compatibility	TTL-level - accepts standard 0.8 V / 2.0 V logic thresholds; no level translation needed

Pinout & Package

SN74AS821ANT is housed in a 24-pin plastic dual in-line package (PDIP-24) with 0.600-inch body width and through-hole mounting. Pin spacing follows JEDEC MS-001 standard.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 3, 4, 5, 6, 7, 8, 9, 10	Data Inputs (D1–D10)	Asynchronous data inputs for first 10-bit section; sampled on rising CLK edge
11, 12, 13, 14, 15, 16, 17, 18, 19, 20	Data Inputs (D11–D20)	Asynchronous data inputs for second 10-bit section; sampled on same rising CLK edge
21	CLK	Common clock input for both 10-bit sections; edge-triggered on rising transition
22	CLR	Active-low asynchronous clear; resets all 20 outputs (Q/Q̅) independently
23, 24	V_CC, GND	Power supply pins; decoupling capacitor placement critical for 100 MHz stability

Key Features

Feature	Design Value
Dual 10-bit latch architecture	Enables simultaneous registration of two independent 10-bit data words using shared clock and clear
Rising-edge clock triggering	Ensures deterministic sampling aligned to system clock edges; eliminates metastability risk in synchronous designs
True + complement outputs per bit	Eliminates need for external inverters in bus-driver or differential signaling configurations
20 mA output drive capability	Supports direct connection to multiple LS-TTL loads without buffer ICs or current-limiting resistors

Applications

Industrial Backplane Register	Legacy Data Acquisition Interface
Use Scenario: Latching parallel sensor data from 20-channel ADC modules onto a shared ISA-style backplane bus. IC Role / Device Role / Timing Role: Dual 10-bit synchronous register providing clock-aligned data capture and bus isolation. Use Value: Eliminates timing skew between channels by latching all 20 bits on a single CLK edge with sub-20 ns delay matching.	Use Scenario: Holding status flags and control commands in a programmable logic controller (PLC) I/O module. IC Role / Device Role / Timing Role: High-reliability D-flip-flop array for non-volatile state storage during scan cycles. Use Value: Guaranteed 20 mA drive ensures robust flag visibility across long ribbon-cable runs under EMI-prone factory conditions.
Test Equipment Pattern Generator	Avionics Maintenance Diagnostic Bus
Use Scenario: Generating precise 20-bit stimulus patterns synchronized to a master test clock in ATE systems. IC Role / Device Role / Timing Role: Edge-triggered pattern register feeding FPGA-based waveform engines. Use Value: 100 MHz max clock rate supports >100 Mbit/s pattern throughput with deterministic setup/hold timing.	Use Scenario: Capturing discrete switch positions and annunciator states in legacy ARINC-429 maintenance interfaces. IC Role / Device Role / Timing Role: Synchronous input latch ensuring fault-tolerant sampling of mechanical contact closures. Use Value: Asynchronous CLR allows immediate reset of all status bits upon power-up or fault recovery without software intervention.

Industrial Backplane Register

Legacy Data Acquisition Interface

Use Scenario: Latching parallel sensor data from 20-channel ADC modules onto a shared ISA-style backplane bus.

IC Role / Device Role / Timing Role: Dual 10-bit synchronous register providing clock-aligned data capture and bus isolation.

Use Value: Eliminates timing skew between channels by latching all 20 bits on a single CLK edge with sub-20 ns delay matching.

Use Scenario: Holding status flags and control commands in a programmable logic controller (PLC) I/O module.

IC Role / Device Role / Timing Role: High-reliability D-flip-flop array for non-volatile state storage during scan cycles.

Use Value: Guaranteed 20 mA drive ensures robust flag visibility across long ribbon-cable runs under EMI-prone factory conditions.

Test Equipment Pattern Generator

Avionics Maintenance Diagnostic Bus

Use Scenario: Generating precise 20-bit stimulus patterns synchronized to a master test clock in ATE systems.

IC Role / Device Role / Timing Role: Edge-triggered pattern register feeding FPGA-based waveform engines.

Use Value: 100 MHz max clock rate supports >100 Mbit/s pattern throughput with deterministic setup/hold timing.

Use Scenario: Capturing discrete switch positions and annunciator states in legacy ARINC-429 maintenance interfaces.

IC Role / Device Role / Timing Role: Synchronous input latch ensuring fault-tolerant sampling of mechanical contact closures.

Use Value: Asynchronous CLR allows immediate reset of all status bits upon power-up or fault recovery without software intervention.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74F821N	Lower speed (50 MHz max), higher propagation delay (25 ns typ), same PDIP-24 pinout	Suitable for cost-sensitive, lower-frequency bus interfaces where timing margin is relaxed	Choose SN74F821N only if clock rates ≤50 MHz and 5 ns additional delay is acceptable
SN74ALS821N	ALS family: lower power (20 mW avg), slower (40 MHz max), 30 ns propagation delay	Better suited for low-power embedded controllers where thermal budget limits AS-family dissipation	Select SN74ALS821N when power consumption < 30 mW is mandatory and speed is secondary

Compared with SN74F821N and SN74ALS821N, the SN74AS821ANT delivers the highest speed and lowest delay among the three, making it the sole choice for 100 MHz synchronous bus latching-though at higher static and dynamic power consumption.

Availability

SN74AS821ANT is available at Aetrix Electronics and suitable for industrial control backplanes, legacy data acquisition systems, and test equipment pattern generation requiring stable component supply and long-term obsolescence management.

Supply support for SN74AS821ANT 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 specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74AS821ANT belongs to TI's legacy Advanced Schottky TTL logic family, engineered specifically for high-speed, noise-immune parallel data registration in mission-critical industrial and test systems.

FAQ

What is the maximum operating frequency of the SN74AS821ANT?

The SN74AS821ANT supports a maximum clock frequency of 100 MHz under recommended operating conditions (V_CC = 5 V, T_A = 25°C). This rating is guaranteed across the commercial temperature range (0°C to 70°C) and validated by TI's characterization data. The SN74AS821ANT achieves this speed via Advanced Schottky TTL circuitry, which minimizes propagation delay while maintaining noise immunity. Designers must ensure clean clock edges and proper decoupling to sustain full-rate operation.

Does the SN74AS821ANT support independent clear for each 10-bit section?

No, the SN74AS821ANT provides only one active-low asynchronous clear (CLR) input that resets all 20 outputs simultaneously. There is no provision for independent clearing of the two 10-bit sections. This design simplifies control logic in systems requiring coordinated reset of parallel data paths. The SN74AS821ANT's shared CLR aligns with its intended use in bus interface and backplane register applications where global synchronization is preferred over sectional control.

Can the SN74AS821ANT be used with 3.3-V logic systems?

The SN74AS821ANT is specified only for 5-V operation and is not 3.3-V tolerant. Its inputs require TTL-level thresholds (0.8 V low, 2.0 V high), and outputs swing fully to 5 V. Direct interfacing with 3.3-V logic risks overvoltage damage and violates absolute maximum ratings. To integrate the SN74AS821ANT into mixed-voltage systems, level-shifting buffers or voltage translators must be used. The SN74AS821ANT itself does not support dual-supply or I/O-tolerant operation.

What is the fan-out capability of each output on the SN74AS821ANT?

Each output of the SN74AS821ANT can drive up to 10 LS-TTL loads, corresponding to a guaranteed 20 mA sink/source capability (I_OL/I_OH). This fan-out rating is verified under worst-case conditions (V_CC = 4.75 V, T_A = 70°C) and ensures reliable signal integrity across standard PCB traces. The SN74AS821ANT's high drive strength eliminates the need for external buffer ICs in most industrial backplane implementations, reducing component count and board space.

Is the SN74AS821ANT still in active production by Texas Instruments?

Texas Instruments lists the SN74AS821ANT as active and available for new designs, with no announced discontinuance. TI maintains long-term supply commitments for select legacy logic devices, including the AS-series, due to sustained demand in industrial and test equipment markets. Aetrix Electronics sources the SN74AS821ANT through authorized TI distribution channels to ensure authenticity and traceability. Customers should verify current status via TI's official product page before finalizing high-volume procurement.

SN74AS821ANT Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74AS

Package/Case:: 24-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Obsolete

Function:: Standard

Type:: D-Type

Output Type:: Tri-State, Non-Inverted

Number of Elements:: 1

Number of Bits per Element:: 10

Clock Frequency:: -

Max Propagation Delay @ V, Max CL:: 13ns @ 5V, 50pF

Trigger Type:: Positive Edge

Current - Output High, Low:: 24mA, 48mA

Voltage - Supply:: 4.5V ~ 5.5V

Current - Quiescent (Iq):: 88 mA

Input Capacitance:: -

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 24-PDIP

SN74AS821ANT FAQ

1.How can I place an order for SN74AS821ANT through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74AS821ANT 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 SN74AS821ANT reliable?

The price and inventory of SN74AS821ANT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS821ANT is usually 5 days.

3.What payment methods are accepted for SN74AS821ANT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS821ANT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74AS821ANT?

SN74AS821ANT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74AS821ANT 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 SN74AS821ANT?

For technical support, including SN74AS821ANT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS821ANT requirements.

6.How does Aetrix verify that SN74AS821ANT is sourced from the original manufacturer or authorized distributors?

All SN74AS821ANT 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 SN74AS821ANT meets industry standards.

7.What is the process for return or replacement of SN74AS821ANT?

All SN74AS821ANT units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS821ANT, 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 SN74AS821ANT part is unused and in its original packaging.

Return procedure for SN74AS821ANT:

1.Submit a request within 90 days.

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

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