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onsemi DM74AS21N
- Part No.:
- DM74AS21N
- Manufacturer:
- onsemi
- Category:
- Gates and Inverters
- Package:
- 14-DIP (0.300", 7.62mm)
- Datasheet:
-
DM74AS21N.pdf
- Description:
- IC GATE AND 2CH 4-INP 14MDIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,802
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Product details
Overview
DM74AS21N from Fairchild Semiconductor is a dual 4-input AND gate IC in a 14-lead PDIP package, operating at VCC = 4.5–5.5 V, with propagation delays of 1–6 ns (tPLH/tPHL), output drive capability of −30 mA (IO) and 20 mA (IOL), and guaranteed performance across 0°C to +70°C. It performs discrete logic gating in TTL-based control and data path circuits.
For engineers reviewing the DM74AS21N datasheet, pinout, applications, or equivalent options, key selection factors include its 4-input per gate architecture, Schottky TTL compatibility, 50 pF load switching specs, and PDIP-14 mechanical footprint for through-hole prototyping and industrial control boards.
Technical Context
The DM74AS21N implements two independent AND gates using advanced oxide-isolated, ion-implanted Schottky TTL technology-enabling higher speed and lower power than standard Schottky TTL. Each gate accepts four inputs (A–D) and delivers a single active-HIGH output (Y), with logic thresholds defined by VIH ≥ 2.0 V and VIL ≤ 0.8 V.
It operates within a recommended VCC range of 4.5–5.5 V and supports full-rail input voltage tolerance up to ±7 V. Output stages are rated for IOL = 20 mA (sink) and IOH = −2 mA (source), with ICC ranging from 2.9 mA (outputs HIGH) to 12 mA (outputs LOW) under worst-case supply conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL systems and noise margin stability |
| tPLH / tPHL | 1 ns (min) to 6 ns (max) - defines maximum signal path delay per gate under 50 pF load and 500 Ω RL |
| IOL / IOH | 20 mA sink / −2 mA source - supports direct driving of multiple TTL inputs or small LEDs without buffering |
| VIH / VIL | ≥2.0 V HIGH threshold / ≤0.8 V LOW threshold - guarantees robust noise immunity in mixed-logic environments |
| Operating Temp | 0°C to +70°C - validated for commercial-grade embedded control and instrumentation applications |
| Package | N14A - 14-lead PDIP, 0.300" wide, through-hole mountable with JEDEC MS-001 compliance |
Pinout & Package
DM74AS21N is housed in a 14-lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001 compliant, 0.300" wide body with 0.100" lead pitch. Thermal resistance θJA is 84.0°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 13, 12 | Gate 1 Inputs A–D | Four independent logic inputs for first AND gate; all must be HIGH for output Y1 (pin 3) to assert |
| 3 | Gate 1 Output Y1 | Active-HIGH AND result of pins 1,2,13,12; drives TTL-compatible loads up to 20 mA |
| 4, 5, 6, 11 | Gate 2 Inputs A–D | Four independent logic inputs for second AND gate; all must be HIGH for output Y2 (pin 10) to assert |
| 10 | Gate 2 Output Y2 | Active-HIGH AND result of pins 4,5,6,11; electrically isolated from Gate 1 |
| 7 | GND | Ground reference for both gates and internal bias networks |
| 14 | VCC | +5 V supply rail; powers both gates and defines logic thresholds and output swing |
Key Features
| Feature | Design Value |
|---|---|
| Advanced Schottky TTL process | Oxide-isolated, ion-implanted fabrication enables faster switching and lower power vs. standard Schottky TTL |
| Full temperature & VCC spec guarantee | Propagation delay and DC parameters validated over 0°C to +70°C and 4.5–5.5 V - no derating needed |
| 50 pF switching characterization | AC performance specified at realistic capacitive loading - simplifies timing analysis in board-level designs |
| Pin-for-pin compatibility | Direct replacement for 74S21, 74LS21, and 74ALS21 in existing PDIP layouts - no PCB change required |
Applications
| Industrial Control Logic | Test Equipment Signal Gating |
|---|---|
Use Scenario: Enabling multi-sensor interlock signals before actuating safety relays in PLC-based machinery. IC Role / Device Role / Timing Role: Dual 4-input AND gate performing synchronous enable validation across four independent fault channels. Use Value: Ensures only when all four safety conditions are met does the output assert - eliminating single-point failure risk in hardware-enforced shutdown paths. | Use Scenario: Selecting one of 16 test waveform channels based on 4-bit address decoding in automated test fixtures. IC Role / Device Role / Timing Role: Two independent 4-input AND gates used as parallel channel-enable logic blocks with common address lines. Use Value: Provides deterministic, race-free channel selection with sub-6 ns propagation - critical for synchronized stimulus-response timing in ATE systems. |
| Digital Instrumentation Bus Control | Legacy System Logic Retrofit |
Use Scenario: Arbitrating access to shared analog-to-digital converter resources among four microcontroller peripherals. IC Role / Device Role / Timing Role: Gate-level bus grant logic ensuring exclusive ADC access only when all requesting peripherals assert readiness. Use Value: Delivers deterministic priority resolution with TTL-compatible drive strength - avoids metastability in mixed-vendor digital subsystems. | Use Scenario: Replacing obsolete 74S21 logic in aging avionics maintenance test sets requiring long-term component availability. IC Role / Device Role / Timing Role: Drop-in functional and pinout replacement for legacy Schottky TTL AND gates in repair and sustainment programs. Use Value: Maintains original timing margins and interface levels while extending service life via modern manufacturing and extended lifecycle support. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual 4-input AND gate applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS21N | Identical logic function, pinout, and AC/DC specs; manufactured by Texas Instruments with same AS-series Schottky process | No functional deviation; qualified for identical commercial temperature range (0°C to +70°C) | Preferred for TI-aligned BOMs or dual-sourcing requirements where TI logistics are prioritized |
| 74F21PC | Fast TTL variant with slightly faster tPLH/tPHL (typ. 4.5 ns vs. 5 ns), but higher ICC (14 mA vs. 12 mA max) and narrower VCC range (4.75–5.25 V) | Better suited for high-speed clocked logic; less tolerant of supply variation or wide-temp operation | Select when sub-5 ns typical delay is mandatory and supply regulation is tight; avoid in unregulated 5 V rails |
Compared with SN74AS21N, DM74AS21N offers identical functionality and sourcing continuity from Fairchild's legacy portfolio; versus 74F21PC, it trades marginal speed for broader VCC tolerance and lower static current - making it more robust in field-deployed commercial systems.
Availability
DM74AS21N is available at Aetrix Electronics and suitable for industrial control logic, test equipment signal gating, digital instrumentation bus control, and legacy system logic retrofit requiring stable component supply and long-term obsolescence management.
Supply support for DM74AS21N 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
Fairchild Semiconductor was a U.S.-based semiconductor company specializing in analog and discrete power products, acquired by ON Semiconductor in 2016; its legacy logic families remain widely supported.
The DM74AS21N belongs to the Advanced Schottky TTL (AS) logic family, designed for high-speed, low-power digital control in commercial-grade instrumentation, industrial automation, and test equipment where reliability and pin compatibility with earlier TTL variants are essential.
FAQ
What logic family does the DM74AS21N belong to, and how does it compare to standard TTL?
The DM74AS21N belongs to the Advanced Schottky TTL (AS) family. It uses oxide-isolated, ion-implanted Schottky technology to achieve faster switching (1–6 ns propagation delay) and lower power consumption than standard TTL or even earlier Schottky (74S) variants. Unlike standard TTL, DM74AS21N guarantees performance across the full 0°C to +70°C range and 4.5–5.5 V supply, with improved noise margins and drive capability - all while maintaining pin compatibility with 74S21, 74LS21, and 74ALS21. The DM74AS21N is fully backward-compatible in both function and layout.
Is the DM74AS21N pin compatible with other dual 4-input AND gate ICs?
Yes, the DM74AS21N is functionally and pin-for-pin compatible with 74S21, 74LS21, and 74ALS21 in the same 14-lead PDIP package (N14A). Pin assignments for inputs, outputs, VCC, and GND match exactly across these families. This allows direct substitution in existing designs without PCB modification - provided the system's timing and drive requirements align with the AS-series specifications. The DM74AS21N retains identical pinout and electrical interface behavior, making it ideal for drop-in upgrades or obsolescence replacement.
What are the absolute maximum ratings for the DM74AS21N, and why do they matter in circuit design?
The DM74AS21N has an absolute maximum supply voltage of 7 V, input voltage limit of 7 V, and operating temperature range of 0°C to +70°C. Exceeding these values risks permanent device damage, even if briefly. These limits define the safe boundaries beyond which reliability is not assured - for example, transient overshoot on VCC or ESD events at inputs must be clamped below 7 V. Designers use these ratings to size protection components and validate worst-case stress scenarios. The DM74AS21N's actual recommended operating conditions (4.5–5.5 V, 0°C–70°C) ensure guaranteed parametric performance - always design within those, not the absolute maxima.
Can the DM74AS21N drive multiple TTL inputs directly, and what is its fan-out capability?
Yes, the DM74AS21N can directly drive multiple standard TTL inputs. With IOL = 20 mA (LOW-level output current) and IIH = 20 µA per TTL input, its theoretical DC fan-out is 1000. In practice, AC loading and noise margins reduce usable fan-out to ~20–30 inputs under typical 50 pF conditions. Its −2 mA IOH (HIGH-level output current) supports ~100 TTL inputs in HIGH state, though propagation delay increases with capacitive load. For reliable timing-critical applications, the DM74AS21N is best used to drive ≤10 TTL loads or buffered interfaces - especially when operating near its 6 ns max tPHL/tPLH limit.
Does the DM74AS21N require external pull-up or pull-down resistors on unused inputs?
Yes, unused inputs on the DM74AS21N must be terminated to a valid logic level - either VCC (for HIGH) or GND (for LOW) - to prevent floating nodes that cause increased power consumption, oscillation, or erratic output behavior. Because each AND gate requires all four inputs HIGH to assert its output, leaving any input unconnected may result in unpredictable Y1 or Y2 states due to noise coupling. A 1–10 kΩ pull-up resistor to VCC is recommended for unused inputs intended to be HIGH; pull-downs are acceptable if logic function requires LOW. This practice ensures stable operation and matches the DM74AS21N's specified VIH/VIL thresholds.
DM74AS21N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74AS
- Package/Case:
- 14-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- AND Gate
- Number of Circuits:
- 2
- Number of Inputs:
- 4
- Features:
- -
- Voltage - Supply:
- 4.5V ~ 5.5V
- Current - Quiescent (Max):
- -
- Current - Output High, Low:
- 2mA, 20mA
- Input Logic Level - Low:
- 0.8V
- Input Logic Level - High:
- 2V
- Max Propagation Delay @ V, Max CL:
- 6ns @ 5V, 50pF
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 14-MDIP
DM74AS21N FAQ
1.How can I place an order for DM74AS21N through Aetrix?
Please submit a Request for Quotation (RFQ) for DM74AS21N 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 DM74AS21N reliable?
The price and inventory of DM74AS21N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DM74AS21N is usually 5 days.
3.What payment methods are accepted for DM74AS21N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DM74AS21N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DM74AS21N?
DM74AS21N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DM74AS21N 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 DM74AS21N?
For technical support, including DM74AS21N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DM74AS21N requirements.
6.How does Aetrix verify that DM74AS21N is sourced from the original manufacturer or authorized distributors?
All DM74AS21N 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 DM74AS21N meets industry standards.
7.What is the process for return or replacement of DM74AS21N?
All DM74AS21N units undergo pre-shipment inspection (PSI). If there is an issue with DM74AS21N, 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 DM74AS21N part is unused and in its original packaging.
Return procedure for DM74AS21N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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