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onsemi DM74ALS21AN
- Part No.:
- DM74ALS21AN
- Manufacturer:
- onsemi
- Category:
- Gates and Inverters
- Package:
- 14-DIP (0.300", 7.62mm)
- Datasheet:
-
DM74ALS21AN.pdf
- Description:
- IC GATE AND 2CH 4-INP 14MDIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,229
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Product details
Overview
DM74ALS21AN from Fairchild Semiconductor is a dual 4-input AND gate logic IC in a 14-lead PDIP package, operating at VCC = 4.5–5.5 V with tPLH ≤ 15 ns, tPHL ≤ 10 ns, and IOL = 8 mA drive capability. It performs two independent Boolean AND functions (Y₁ = A₁B₁C₁D₁, Y₂ = A₂B₂C₂D₂) and is used in digital control, address decoding, and bus gating in industrial TTL systems.
For engineers reviewing the DM74ALS21AN datasheet, pinout, applications, or equivalent options, key selection considerations include guaranteed AC performance over 0°C to +70°C, Schottky TTL compatibility, 50 pF load switching specs, input clamp voltage of –1.5 V, and output drive asymmetry (IOH = –0.4 mA / IOL = 8 mA).
Technical Context
This device implements two independent positive-logic AND gates using advanced oxide-isolated, ion-implanted Schottky TTL technology. Each gate accepts four inputs and delivers one active-high output with defined VIH = 2.0 V and VIL = 0.8 V thresholds.
It operates within a strict 4.5–5.5 V supply range and guarantees propagation delays (tPLH/tPHL) across full temperature (0°C to +70°C) and load (CL = 50 pF, RL = 500 Ω). Output voltage levels are specified as VOH ≥ VCC – 2 V and VOL ≤ 0.5 V under rated load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation in standard 5 V TTL systems with ±10% rail tolerance. |
| tPLH / tPHL | 4–15 ns / 2–10 ns - Defines maximum signal path delay for synchronous timing-critical logic stages. |
| IOL / IOH | 8 mA / –0.4 mA - Supports driving multiple TTL inputs (fan-out ≥ 20) but limited high-side sourcing. |
| VIL / VIH | 0.8 V / 2.0 V - Compatible with standard TTL input thresholds for seamless integration. |
| Operating Temp | 0°C to +70°C - Rated for commercial-grade industrial control and instrumentation environments. |
| Input Clamp | –1.5 V - Protects inputs against negative transients without external clamping diodes. |
Pinout & Package
DM74ALS21AN is housed in a 14-lead plastic dual in-line package (PDIP), JEDEC MS-001, 0.300" wide. Pin spacing is 0.100", body width 0.300", and total length 0.770".
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 13, 12 | Gate 1 Inputs A–D | Four logic inputs for first AND gate; all must be HIGH for output Y₁ to assert. |
| 3 | Gate 1 Output Y₁ | Active-HIGH AND result; sinks up to 8 mA when LOW, sources –0.4 mA when HIGH. |
| 4, 5, 6, 11 | Gate 2 Inputs A–D | Four logic inputs for second independent AND gate. |
| 10 | Gate 2 Output Y₂ | Active-HIGH AND result; electrically identical to Y₁, fully isolated from Gate 1. |
| 7 | GND | Logic ground reference; must be connected to system 0 V plane with low-inductance path. |
| 14 | VCC | +5 V power supply; requires local 0.1 µF ceramic decoupling adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Advanced Schottky TTL Process | Oxide-isolated, ion-implanted fabrication enables higher speed and lower power than standard TTL. |
| Full Temperature Spec Guarantee | All AC/DC parameters validated from 0°C to +70°C - eliminates derating calculations for commercial designs. |
| 50 pF Load Switching Specs | Propagation delays characterized at realistic PCB trace + gate loading - supports accurate timing margin analysis. |
| Pin-for-Pin Compatibility | Direct replacement for 74S21 and 74LS21 in existing layouts - no PCB revision required. |
| Input Clamp Protection | VIK = –1.5 V allows safe handling of negative input spikes without external protection components. |
Applications
| Industrial Control Logic | Memory Address Decoding |
|---|---|
Use Scenario: Enable/disable signal paths in programmable logic controllers based on multi-bit status flags. IC Role / Device Role / Timing Role: Dual AND gate performing real-time combinational enable logic for relay drivers and sensor interface modules. Use Value: Guaranteed 10 ns max tPHL ensures deterministic response within 200 ns control cycles at 5 MHz clock rates. | Use Scenario: Select specific memory banks in 8-bit microprocessor systems using 4-bit address subsets. IC Role / Device Role / Timing Role: Address gating element that asserts chip-select only when all four address bits match a decoded window. Use Value: 8 mA IOL drives multiple memory chip-select inputs directly, eliminating buffer stages and reducing BOM count. |
| Bus Arbitration Interface | Digital Instrumentation Signal Gating |
Use Scenario: Coordinate access to shared data buses among multiple peripherals in test equipment backplanes. IC Role / Device Role / Timing Role: Priority encoder front-end logic that validates grant signals only when all arbitration request bits align. Use Value: Input thresholds (VIH = 2.0 V, VIL = 0.8 V) ensure noise immunity against crosstalk in dense backplane routing. | Use Scenario: Gate analog-to-digital conversion triggers in multichannel data loggers based on synchronized enable conditions. IC Role / Device Role / Timing Role: Synchronizing AND gate that releases ADC start pulses only when both clock and ready signals are asserted. Use Value: Propagation delay variation ≤ 5 ns (tPLH–tPHL spread) minimizes jitter in time-critical sampling windows. |
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 |
|---|---|---|---|
| SN74ALS21N | Identical electrical specs and pinout; manufactured by Texas Instruments under same ALS family spec. | No functional difference; validated for same industrial temperature range and load conditions. | Select when TI-sourced supply chain alignment or dual-sourcing strategy is required. |
| DM74LS21N | Lower speed (tPLH/tPHL up to 25 ns), higher power (ICC ≈ 19 mA vs. 1.4–2.3 mA), same pinout. | Suitable for non-critical timing paths where power efficiency is secondary to cost or legacy stock use. | Choose only if design tolerates 2× slower propagation and can accommodate 8× higher quiescent current. |
Compared with SN74ALS21N, DM74ALS21AN offers identical performance and drop-in usability; versus DM74LS21N, it delivers 40% faster switching and 85% lower ICC, making it optimal for timing-sensitive, power-constrained TTL subsystems.
Availability
DM74ALS21AN is available at Aetrix Electronics and suitable for industrial control logic, memory address decoding, and bus arbitration applications requiring stable component supply and long-term obsolescence management.
Supply support for DM74ALS21AN 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 designer and manufacturer of analog and mixed-signal semiconductors, acquired by ON Semiconductor in 2016. Known for industry-standard TTL, CMOS, and power IC families.
The DM74ALS21AN belongs to Fairchild's Advanced Low-Power Schottky (ALS) logic series, engineered for high-speed, low-power digital systems where compatibility with legacy TTL infrastructure is essential.
FAQ
What logic family does DM74ALS21AN belong to, and how does it differ from standard TTL?
DM74ALS21AN belongs to the Advanced Low-Power Schottky (ALS) TTL family. It uses ion-implanted Schottky technology to achieve faster switching (≤15 ns propagation delay) and lower power consumption (ICC = 1.4–2.3 mA) than standard TTL or LS variants. Unlike basic TTL, DM74ALS21AN guarantees AC performance across the full 0°C to +70°C range and specifies behavior at 50 pF load capacitance - critical for reliable timing in modern board layouts.
Is DM74ALS21AN pin-compatible with other dual 4-input AND gates like the 74S21 or 74LS21?
Yes, DM74ALS21AN is functionally and pin-for-pin compatible with both 74S21 and 74LS21 devices. Its pinout matches the standard 14-lead DIP configuration: inputs and outputs map identically, and VCC (pin 14) and GND (pin 7) positions are unchanged. This allows direct replacement in existing designs without PCB modification, provided timing margins accommodate the improved speed of DM74ALS21AN.
What are the absolute maximum ratings for DM74ALS21AN, and why do they matter in circuit design?
The absolute maximum ratings for DM74ALS21AN are VCC = 7 V, VI = 7 V, and operating temperature = 0°C to +70°C. Exceeding these - especially VCC > 5.5 V or VI < –1.5 V - risks permanent damage due to junction breakdown or latch-up. These limits define the safety envelope: designers must ensure power supply regulation, input clamping, and thermal management stay within bounds to guarantee long-term reliability in deployed systems using DM74ALS21AN.
Can DM74ALS21AN drive standard TTL loads directly, and what is its fan-out capability?
Yes, DM74ALS21AN can drive standard TTL loads directly. With IOL = 8 mA and VIH = 2.0 V, it supports a DC fan-out of ≥20 standard TTL inputs (each drawing ~0.4 mA). Its IOH = –0.4 mA limits high-level sourcing, so it is best used in configurations where outputs primarily sink current - e.g., driving LED indicators or enabling active-low inputs. For bidirectional or high-source-demand applications, buffering is recommended.
Does DM74ALS21AN require external decoupling capacitors, and what value is recommended?
Yes, DM74ALS21AN requires local power supply decoupling to suppress switching noise and prevent supply rail collapse during output transitions. A 0.1 µF ceramic capacitor placed between VCC (pin 14) and GND (pin 7), with leads ≤ 5 mm long and mounted directly adjacent to the package, is recommended. This mitigates transient current spikes from simultaneous input transitions and ensures stable VOH/VOL levels across the operating temperature range for consistent DM74ALS21AN performance.
DM74ALS21AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74ALS
- 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:
- 400µA, 8mA
- Input Logic Level - Low:
- 0.8V
- Input Logic Level - High:
- 2V
- Max Propagation Delay @ V, Max CL:
- 15ns @ 5V, 50pF
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 14-MDIP
DM74ALS21AN FAQ
1.How can I place an order for DM74ALS21AN through Aetrix?
Please submit a Request for Quotation (RFQ) for DM74ALS21AN 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 DM74ALS21AN reliable?
The price and inventory of DM74ALS21AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DM74ALS21AN is usually 5 days.
3.What payment methods are accepted for DM74ALS21AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DM74ALS21AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DM74ALS21AN?
DM74ALS21AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DM74ALS21AN 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 DM74ALS21AN?
For technical support, including DM74ALS21AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DM74ALS21AN requirements.
6.How does Aetrix verify that DM74ALS21AN is sourced from the original manufacturer or authorized distributors?
All DM74ALS21AN 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 DM74ALS21AN meets industry standards.
7.What is the process for return or replacement of DM74ALS21AN?
All DM74ALS21AN units undergo pre-shipment inspection (PSI). If there is an issue with DM74ALS21AN, 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 DM74ALS21AN part is unused and in its original packaging.
Return procedure for DM74ALS21AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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