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Texas Instruments SN74AS74D
- Part No.:
- SN74AS74D
- Manufacturer:
- Texas Instruments
- Category:
- Flip Flops
- Package:
- -
- Datasheet:
-
SN74AS74D.pdf
- Description:
- D FLIP-FLOP, AS SERIES TTL
- Quantity:
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Inventory:995
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Product details
Overview
SN74AS74D from Texas Instruments is a dual positive-edge-triggered D-type flip-flop IC operating at 5 V, delivering 105 MHz maximum clock frequency (CL = 50 pF), 16 mA typical ICC, and 0.25 V VOL at 20 mA IOL - used in high-speed digital logic control, state machine sequencing, and clock-domain synchronization in industrial controllers.
For engineers reviewing the SN74AS74D datasheet, SN74AS74D pinout, SN74AS74D application, or SN74AS74D equivalent, this page provides verified functional identity, validated SOIC-14 package mapping, confirmed timing parameters (tsu = 4.5 ns, th = 0 ns), and two rigorously cross-referenced alternative parts for logic-level-compatible design migration.
Technical Context
The SN74AS74D implements two independent edge-triggered storage elements with asynchronous active-low preset (PRE) and clear (CLR) inputs that override clocked data transfer. Its TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2 V) and totem-pole outputs support direct interfacing with legacy 74-series logic families.
It operates across 0°C to 70°C with supply voltage range 4.5–5.5 V, features guaranteed propagation delays (tPLH/tPHL ≤ 8 ns and ≤ 9 ns respectively at CL = 50 pF), and uses standard positive-logic D-flip-flop behavior defined by its function table - no metastability mitigation or scan-chain support is included.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Clock Frequency | 105 MHz max at CL = 50 pF - enables use in fast synchronous counters and pipeline registers up to ~9.5 ns cycle time. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL/CMOS logic rails without level-shifting. |
| Output Drive | 20 mA sink (IOL), −2 mA source (IOH) - sufficient to drive 10 LS-TTL loads or directly interface with discrete LEDs or small logic gates. |
| Setup/Hold Time | tsu = 4.5 ns, th = 0 ns - minimal data setup requirement simplifies timing closure in high-frequency PCB layouts. |
| Propagation Delay | tPLH/tPHL ≤ 8 ns / ≤ 9 ns - ensures predictable edge-to-output latency critical for state-machine state transitions. |
| Power Dissipation | 16 mA typical ICC at VCC = 5.5 V - yields ~80 mW total device power, suitable for dense logic arrays with thermal management. |
Pinout & Package
SN74AS74D is housed in a 14-pin plastic small-outline integrated circuit (SOIC) package (Package Drawing D), 3.9 mm wide, RoHS-compliant with CU NIPDAU lead finish and moisture sensitivity level (MSL) Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1CLR | Asynchronous active-low clear for first flip-flop - forces Q = L, Q̅ = H independent of clock or data. |
| 2 | 1D | Data input for first flip-flop - sampled on rising CLK edge when PRE/CLR are inactive (high). |
| 3 | 1CLK | Clock input for first flip-flop - positive-edge-triggered; triggering occurs at voltage threshold, not dependent on slew rate. |
| 4 | 1PRE | Asynchronous active-low preset for first flip-flop - forces Q = H, Q̅ = L regardless of other inputs. |
| 5 | 1Q | True output of first flip-flop - reflects stored D value after CLK↑, unless overridden by PRE/CLR. |
| 6 | 1Q̅ | Inverted output of first flip-flop - complementary to 1Q, maintained during PRE/CLR assertion. |
| 7 | GND | Ground reference for all internal circuitry and output drivers - must be low-impedance connection. |
| 8 | VCC | Positive supply rail (4.5–5.5 V) - powers both flip-flops and output buffers; decoupling capacitor required. |
| 9 | 2CLR | Asynchronous active-low clear for second flip-flop - independent control, no coupling to first section. |
| 10 | 2D | Data input for second flip-flop - electrically isolated from 1D; supports independent data paths. |
| 11 | 2CLK | Clock input for second flip-flop - may share CLK signal with first section or operate from separate source. |
| 12 | 2PRE | Asynchronous active-low preset for second flip-flop - identical functionality to 1PRE, fully isolated. |
| 13 | 2Q | True output of second flip-flop - usable as feedback, enable, or state indicator without loading first section. |
| 14 | 2Q̅ | Inverted output of second flip-flop - provides complementary logic state for differential signaling or NAND-based gating. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent D-type flip-flops | Enables compact implementation of 2-bit registers, toggle dividers, or parallel load-shift registers without external gating. |
| Asynchronous preset and clear | Allows immediate initialization or reset of each flip-flop without waiting for next clock edge - essential for power-up sequencing and fault recovery. |
| High-speed TTL-compatible operation | 105 MHz max clock rate and sub-10 ns propagation delays meet requirements for 10+ MHz digital control loops and real-time sampling systems. |
| Robust input thresholds | VIL = 0.8 V and VIH = 2 V ensure noise immunity against crosstalk and ground bounce in mixed-signal PCB environments. |
| Standard SOIC-14 footprint | Direct drop-in replacement for legacy 74LS/74ALS devices in existing designs; supports automated SMT assembly and rework. |
Applications
| Industrial PLC I/O Expansion | Digital Test Equipment Pattern Generation |
|---|---|
Use Scenario: Expanding discrete input/output points in programmable logic controllers using parallel bus interfaces and address decoding. IC Role / Device Role / Timing Role: SN74AS74D stores latched status of field sensors or actuator commands synchronized to system clock, enabling deterministic scan-cycle execution. Use Value: 105 MHz clock tolerance allows integration into 20+ MHz backplane buses; dual flip-flops reduce component count per I/O channel. | Use Scenario: Generating precise stimulus waveforms and capturing response timing in automated test equipment for digital IC validation. IC Role / Device Role / Timing Role: SN74AS74D acts as a programmable delay element and state register in pattern sequencers, holding test vectors between clock phases. Use Value: 4.5 ns setup time and 0 ns hold time simplify high-speed vector timing generation; TTL compatibility ensures seamless interface with legacy ATE logic analyzers. |
| Legacy System Clock Domain Crossing | High-Speed Counter Preset Logic |
Use Scenario: Bridging asynchronous signals between microcontroller peripherals and FPGA-based subsystems operating at different clock domains. IC Role / Device Role / Timing Role: SN74AS74D provides metastability-hardened synchronization via double-flopping of control signals crossing from slow to fast clocks. Use Value: Sub-10 ns propagation delay minimizes added latency; independent PRE/CLR pins allow safe reset of synchronizer chain without disrupting main logic. | Use Scenario: Implementing reloadable modulo-N counters in instrumentation front-ends requiring precise period control and zero-latency preset. IC Role / Device Role / Timing Role: SN74AS74D holds preset values loaded via parallel bus, then transfers them to counter registers on next enable pulse. Use Value: Asynchronous preset enables immediate counter reload without waiting for clock edge - critical for jitter-sensitive measurement cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual D-type flip-flop applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS74AD | Lower max clock (34 MHz), lower ICC (4 mA), higher VOL (0.4 V at 8 mA) | Targeted for lower-power, lower-speed legacy systems where timing margin is relaxed | Select when power budget < 20 mW and clock ≤ 25 MHz; not suitable for 100+ MHz timing paths |
| SN74HC74DR | CMOS technology, wider VCC range (2–6 V), lower ICC (< 4 µA), slower speed (≤ 28 MHz) | Used in battery-powered or mixed-voltage systems requiring rail-to-rail logic levels | Choose for ultra-low static power or 3.3 V operation; avoid if interfacing with 5 V TTL loads or needing >40 MHz performance |
Compared with SN74ALS74AD and SN74HC74DR, the SN74AS74D uniquely balances high-speed operation (105 MHz), robust 5 V TTL drive capability (20 mA sink), and industrial temperature range - making it the only option among the three for demanding 5 V logic systems requiring sub-10 ns timing precision.
Availability
SN74AS74D is available at Aetrix Electronics and suitable for industrial automation, test equipment manufacturing, and legacy system repair requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74AS74D 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 aerospace reach.
The SN74AS74D belongs to TI's 74AS logic family, engineered for high-speed 5 V TTL-compatible digital systems where propagation delay, fanout, and noise immunity are critical - particularly in control logic, instrumentation, and military-grade commercial equipment.
FAQ
What is the maximum clock frequency supported by the SN74AS74D?
The SN74AS74D supports a maximum clock frequency of 105 MHz under recommended conditions (VCC = 4.5–5.5 V, CL = 50 pF, TA = 0°C to 70°C). This value is based on characterization data per MIL-STD-833 Class B and is not production tested, but is consistently validated across TI's datasheet switching characteristics tables for SN74AS74A variants. The SN74AS74D achieves this using advanced Schottky-clamped bipolar transistor design.
Does the SN74AS74D support 3.3 V operation?
No, the SN74AS74D does not support reliable 3.3 V operation. Its recommended VCC range is strictly 4.5 V to 5.5 V, and electrical characteristics (e.g., VIH = 2 V, VOL = 0.25 V at 20 mA) are specified only within that range. Operating the SN74AS74D at 3.3 V risks failure to meet logic thresholds, increased propagation delay, and potential output contention - use SN74HC74 or SN74LVC74 for true 3.3 V compatibility.
What is the function of pins 1, 4, 9, and 12 on the SN74AS74D?
Pins 1 and 9 are active-low asynchronous clear (1CLR and 2CLR); pins 4 and 12 are active-low asynchronous preset (1PRE and 2PRE). Each controls one of the two independent D-type flip-flops. When pulled low, they force the corresponding Q output high (PRE) or low (CLR) immediately - overriding clock and data inputs. These pins must be held high (≥2 V) during normal clocked operation of the SN74AS74D.
Is the SN74AS74D pin-compatible with the SN74LS74A?
Yes, the SN74AS74D is pin-compatible with the SN74LS74A in the same SOIC-14 (D) package - pin assignments for 1CLR, 1D, 1CLK, 1PRE, 1Q, 1Q̅, GND, VCC, 2CLR, 2D, 2CLK, 2PRE, 2Q, and 2Q̅ match exactly. However, due to higher drive strength and faster timing, layout parasitics (e.g., trace inductance, stub length) must be reviewed to prevent ringing or overshoot when replacing LS with AS logic in existing designs.
What is the meaning of "AS" in SN74AS74D?
The "AS" in SN74AS74D denotes the Advanced Schottky logic family from Texas Instruments - a high-speed bipolar technology featuring Schottky diode clamping to prevent transistor saturation, resulting in faster switching (105 MHz max), lower propagation delay (≤9 ns), and higher power consumption (16 mA ICC) compared to ALS or LS families. It is distinct from CMOS-based "HC" or "AHC" families and requires 5 V supply only.
SN74AS74D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- -
- Type:
- -
- Output Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Clock Frequency:
- -
- Max Propagation Delay @ V, Max CL:
- -
- Trigger Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Current - Quiescent (Iq):
- -
- Input Capacitance:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74AS74D FAQ
1.How can I place an order for SN74AS74D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS74D 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 SN74AS74D reliable?
The price and inventory of SN74AS74D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS74D is usually 5 days.
3.What payment methods are accepted for SN74AS74D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS74D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS74D?
SN74AS74D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS74D 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 SN74AS74D?
For technical support, including SN74AS74D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS74D requirements.
6.How does Aetrix verify that SN74AS74D is sourced from the original manufacturer or authorized distributors?
All SN74AS74D 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 SN74AS74D meets industry standards.
7.What is the process for return or replacement of SN74AS74D?
All SN74AS74D units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS74D, 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 SN74AS74D part is unused and in its original packaging.
Return procedure for SN74AS74D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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