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STMicroelectronics 74AC74B
- Part No.:
- 74AC74B
- Manufacturer:
- STMicroelectronics
- Category:
- Flip Flops
- Package:
- 14-DIP (0.300", 7.62mm)
- Datasheet:
-
74AC74B.pdf
- Description:
- IC FF D-TYPE DUAL 1BIT 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,592
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Product details
Overview
74AC74B from STMicroelectronics is a dual D-type flip-flop with asynchronous preset and clear, designed for high-speed synchronous logic in 5V and mixed-voltage systems. It features 300MHz typical maximum clock frequency, ±24mA symmetrical output drive, and operates across 2V–6V supply range. Used in clocked data latching, state machine control, and bus interface synchronization.
For engineers reviewing the 74AC74B datasheet, 74AC74B pinout, 74AC74B application, or 74AC74B equivalent, key selection criteria include propagation delay matching (tPLH/tPHL ≈ 10.0 ns at 5V), 50Ω transmission line drive capability, latch-up immunity, and compatibility with legacy 74-series logic timing and pinout.
Technical Context
The 74AC74B implements two independent edge-triggered D flip-flops, each with asynchronous active-low preset (PR) and clear (CLR) inputs that override clock and data. Its C2MOS sub-micron process enables low ICC (2µA max) and high noise immunity (VNIH/VNIL = 28% VCC min).
Propagation delays are balanced (tPLH ≅ tPHL), and setup/hold times are specified down to –0.2 ns (setup) and +0.2 ns (hold) at 5V, supporting tight timing margins in high-frequency register chains and pipeline stages.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| fMAX | 300 MHz typical at VCC = 5V - supports high-speed data capture up to 300 million state transitions per second |
| VCC Range | 2 V to 6 V - enables interoperability with 3.3V and 5V logic families without level shifters |
| IOL / IOH | ±24 mA minimum - drives 50Ω transmission lines directly with controlled edge rates |
| tPLH / tPHL | 10.0 ns max at VCC = 5V - ensures predictable, matched rise/fall path delays for skew-sensitive registers |
| VNIH / VNIL | 28% VCC minimum - provides robust noise rejection against crosstalk and ground bounce |
| ICC (quiescent) | 2 µA maximum at TA = 25°C - minimizes static power in battery-backed or always-on control logic |
| ts / th | 3.0 ns setup / 2.0 ns hold at VCC = 5V - allows integration into fast clock domains with minimal timing margin overhead |
Pinout & Package
74AC74B is supplied in a 14-pin plastic dual in-line package (DIP-14) per mechanical drawing P001A, with 2.54 mm lead pitch and through-hole mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 13 | 1CLR, 2CLR | Asynchronous active-low reset - forces Q = L, Q̄ = H independently of clock |
| 2, 12 | 1D, 2D | Data input - sampled on rising clock edge and transferred to outputs |
| 3, 11 | 1CK, 2CK | Positive-edge-triggered clock - initiates synchronous state update |
| 4, 10 | 1PR, 2PR | Asynchronous active-low preset - forces Q = H, Q̄ = L independently of clock |
| 5, 9 | 1Q, 2Q | True output - reflects stored D value after clock edge or async control |
| 6, 8 | 1Q̄, 2Q̄ | Inverted output - complementary to Q, useful for toggle or feedback paths |
| 7 | GND | Ground reference - return path for all internal currents and I/O |
| 14 | VCC | Positive supply - powers logic core and output drivers; tolerant of 2–6V operation |
Key Features
| Feature | Design Value |
|---|---|
| Symmetrical output drive | IOH = IOL = 24 mA min - eliminates duty cycle distortion in clock distribution networks |
| Balanced propagation delays | tPLH ≅ tPHL - reduces clock-to-Q skew between true and complement outputs |
| High noise immunity | VNIH = VNIL = 28% VCC min - maintains logic integrity in electrically noisy industrial environments |
| 50Ω transmission line drive | Guaranteed incident-wave switching into 50Ω loads - enables direct connection to PCB traces without external termination |
| Latch-up immunity | Improved vs. standard CMOS - prevents destructive parasitic thyristor conduction during overvoltage transients |
Applications
| Industrial PLC I/O Expansion | Digital Audio Sample Rate Conversion |
|---|---|
Use Scenario: Synchronizing parallel sensor data streams into a central controller under variable EMI conditions. IC Role / Device Role / Timing Role: Dual-register stage isolating asynchronous field inputs from deterministic scan cycles. Use Value: Asynchronous preset/clear enables safe initialization before scan start; 28% VCC noise margin rejects motor-drive coupling. | Use Scenario: Aligning audio sample clocks between ADC and DAC domains operating at different base rates. IC Role / Device Role / Timing Role: Edge-triggered storage element in digital phase-locked loop (DPLL) feedback path. Use Value: Balanced tPLH/tPHL (≤10 ns) minimizes jitter accumulation; 300 MHz fMAX supports oversampling ratios up to 128×. |
| Legacy Bus Interface Logic | Test Equipment Pattern Generation |
Use Scenario: Glue logic bridging 5V microcontroller address/data buses to peripheral memory or display controllers. IC Role / Device Role / Timing Role: Synchronous latch holding write-enable or chip-select strobes with precise edge alignment. Use Value: Pin- and function-compatible with 74LS74 - enables drop-in replacement without PCB redesign. | Use Scenario: Generating deterministic stimulus waveforms for IC functional testing at speeds up to 100 MHz. IC Role / Device Role / Timing Role: High-speed pattern register feeding parallel output pins in automated test equipment (ATE) channels. Use Value: ±24 mA drive sustains signal integrity into 50Ω scope probes or load boards; 2–6V VCC supports mixed-voltage test fixtures. |
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 |
|---|---|---|---|
| SN74AC74N | Same AC electrical specs; identical pinout; TI-manufactured with slightly higher ICC (4 µA max) | No functional difference; validated for same 5V industrial control use cases | Select when sourcing from TI-authorized channels or requiring TI-specific qualification documentation |
| MC74AC74N | Onsemi version; identical timing and drive specs; CL = 50 pF test condition maintained | Same 2–6V operation and noise immunity; minor packaging variation in tape-and-reel marking | Prefer for long-term supply continuity where STMicroelectronics allocation is constrained |
Compared with SN74AC74N and MC74AC74N, the 74AC74B offers identical functional behavior and timing performance but differs in manufacturer-specific process optimization and qualification reporting-making it interchangeable in circuit design while enabling multi-source procurement strategy.
Availability
74AC74B is available at Aetrix Electronics and suitable for industrial PLCs, digital audio converters, legacy bus interfaces, and ATE pattern generators requiring stable component supply across extended temperature ranges (–55°C to +125°C).
Supply support for 74AC74B 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with strong analog and mixed-signal heritage.
The 74AC logic family was developed to deliver high-speed, low-power TTL-compatible CMOS performance for industrial control, instrumentation, and communications infrastructure where reliability and wide supply tolerance are critical.
FAQ
Is 74AC74B compatible with 3.3V logic systems?
Yes - the 74AC74B operates reliably from 2V to 6V, with guaranteed VIH/VIL thresholds at 3.3V (VIH = 2.1V min, VIL = 1.5V max). Its outputs swing rail-to-rail and drive 3.3V CMOS inputs directly without level translation.
What is the meaning of "incident wave switching" in the 50Ω driving specification?
It means the device can launch clean, undistorted logic edges onto 50Ω transmission lines without external series termination - verified by waveform testing where output voltage settles within spec before reflection returns, enabling reliable high-speed interconnects on PCBs.
Can preset and clear be used simultaneously on one flip-flop?
No - asserting both 1PR and 1CLR low simultaneously violates the truth table and results in an undefined output state (Q and Q̄ both high). The datasheet explicitly prohibits this condition; proper sequencing requires only one async control active at a time.
Does 74AC74B require decoupling capacitors in high-speed operation?
Yes - STMicroelectronics recommends 100 nF ceramic capacitors placed within 5 mm of each VCC–GND pair. At 300 MHz fMAX, supply inductance causes significant transient droop; local decoupling maintains stable VCC during simultaneous output switching events.
74AC74B Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74AC
- Package/Case:
- 14-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Set(Preset) and Reset
- Type:
- D-Type
- Output Type:
- Complementary
- Number of Elements:
- 2
- Number of Bits per Element:
- 1
- Clock Frequency:
- 300 MHz
- Max Propagation Delay @ V, Max CL:
- 10ns @ 5V, 50pF
- Trigger Type:
- Positive Edge
- Current - Output High, Low:
- 24mA, 24mA
- Voltage - Supply:
- 2V ~ 6V
- Current - Quiescent (Iq):
- 2 µA
- Input Capacitance:
- 3 pF
- Operating Temperature:
- -55°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-TSSOP
74AC74B FAQ
1.How can I place an order for 74AC74B through Aetrix?
Please submit a Request for Quotation (RFQ) for 74AC74B 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 74AC74B reliable?
The price and inventory of 74AC74B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74AC74B is usually 5 days.
3.What payment methods are accepted for 74AC74B?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74AC74B transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74AC74B?
74AC74B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74AC74B 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 74AC74B?
For technical support, including 74AC74B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74AC74B requirements.
6.How does Aetrix verify that 74AC74B is sourced from the original manufacturer or authorized distributors?
All 74AC74B 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 74AC74B meets industry standards.
7.What is the process for return or replacement of 74AC74B?
All 74AC74B units undergo pre-shipment inspection (PSI). If there is an issue with 74AC74B, 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 74AC74B part is unused and in its original packaging.
Return procedure for 74AC74B:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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