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Texas Instruments CD74HC238E
- Part No.:
- CD74HC238E
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74HC238E.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:7,662
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Product details
Overview
CD74HC238E from Texas Instruments is a high-speed CMOS 3-to-8 line decoder/demultiplexer with active-high outputs, 2 V to 6 V supply operation, typical propagation delay of 13 ns at VCC = 5 V and CL = 15 pF, -55°C to +125°C operating temperature range, and three enable inputs (G2, G1, G0) for cascading. It serves as an address decoder in microcontroller memory expansion systems.
For engineers reviewing the CD74HC238E datasheet, CD74HC238E pinout, CD74HC238E application, or CD74HC238E equivalent, this page delivers verified functional behavior, exact pin roles, real-world timing constraints, thermal performance data, and validated alternative options for industrial control, instrumentation, and embedded logic design.
Technical Context
The CD74HC238E implements a single 3:8 decoder with three address inputs (A0–A2) and three strobe inputs (G2, G1, G0), where G2 is active-high and G1/G0 are active-low. When any strobe is asserted, all eight outputs (Y0–Y7) are driven low - unlike the '138 variant which forces outputs high.
Its output logic is noninverting: only the selected output goes high (active-high) while all others remain low when enabled. The device supports memory address decoding and data routing via demultiplexing, using one strobe input as the data path while A0–A2 select the destination line.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | 3-to-8 line decoder/demultiplexer with active-high outputs |
| VCC Range | 2 V to 6 V - enables direct interface with 3.3 V and 5 V logic families without level shifters |
| tpd (max) | 45 ns at VCC = 4.5 V, CL = 50 pF - defines worst-case address-to-output latency in timing-critical routing |
| Operating Temp | -55°C to +125°C - qualified for extended industrial, aerospace, and automotive under-hood applications |
| IOL/IOH | ±4 mA output drive - sufficient to directly drive multiple LSTTL loads (fanout = 10) or small LEDs |
| Input Leakage | ±1 µA max at 6 V - ensures stable logic states with high-impedance or floating-bus configurations |
| Power Dissipation | Cpd = 67 pF - enables accurate dynamic power estimation at 1 MHz switching frequency |
Pinout & Package
CD74HC238E uses a 16-pin PDIP (plastic dual in-line package) with 25.40 mm × 6.35 mm body size, through-hole mounting, and industry-standard 0.3-inch row spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A0) | Address input 0 | LSB of 3-bit binary address selecting Y0–Y7; must be terminated to VCC or GND if unused |
| 2 (A1) | Address input 1 | Middle bit of address bus; determines output group partitioning in cascaded decoder trees |
| 3 (A2) | Address input 2 | MSB of address; combined with A1/A0, fully selects one of eight outputs |
| 4 (G0) | Active-low enable strobe 0 | Disables all outputs (forces Y0–Y7 low) when logic high; used for hierarchical enable control |
| 5 (G1) | Active-low enable strobe 1 | Second cascade enable; OR'd with G0 and G2 to gate output activity |
| 6 (G2) | Active-high enable strobe 2 | Primary enable signal - must be high for decoder to respond to A2–A0 |
| 7 (Y7) | Output 7 | Active-high decoded output corresponding to A2A1A0 = 111; sinks/source up to 4 mA |
| 8 (GND) | Ground reference | Return path for all internal logic and output currents; requires low-inductance connection |
| 9 (Y6) | Output 6 | Active-high output for A2A1A0 = 110; electrically identical to Y7 in drive strength and timing |
| 10 (Y5) | Output 5 | Active-high output for A2A1A0 = 101; shares same propagation delay spec as Y0–Y7 |
| 11 (Y4) | Output 4 | Active-high output for A2A1A0 = 100; used in 16-bit memory bank selection with parallel '238 devices |
| 12 (Y3) | Output 3 | Active-high output for A2A1A0 = 011; compatible with standard 74-series logic voltage thresholds |
| 13 (Y2) | Output 2 | Active-high output for A2A1A0 = 010; supports TTL/CMOS mixed-signal interfacing |
| 14 (Y1) | Output 1 | Active-high output for A2A1A0 = 001; meets 30% noise margin (NIH/NIL) at VCC = 5 V |
| 15 (Y0) | Output 0 | Active-high output for A2A1A0 = 000; lowest-address output, commonly used for boot memory mapping |
| 16 (VCC) | Positive supply | Power rail for internal logic and output drivers; requires 0.1 µF ceramic bypass capacitor near pin |
Key Features
| Feature | Design Value |
|---|---|
| Active-high output architecture | Enables direct connection to LED anodes or pull-up-based interrupt lines without external inverters |
| Three independent enable inputs | Supports 2-level cascading of up to four CD74HC238E devices for 5-to-32 decoding without glue logic |
| High noise immunity | 30% noise margin (NIL/NIL) at VCC = 5 V ensures reliable operation in electrically noisy industrial environments |
| Wide supply voltage range | 2 V to 6 V operation allows interoperability across 2.5 V, 3.3 V, and 5 V system domains |
| Low dynamic power consumption | 67 pF power dissipation capacitance enables sub-mW operation at 100 kHz toggle rate |
Applications
| Memory Address Decoding | Peripheral I/O Selection |
|---|---|
|
Use Scenario: Selecting one of eight RAM/ROM chips in a microcontroller-based data acquisition system with 16-bit address bus. IC Role / Device Role: Translates upper 3 address bits (A13–A15) into chip-select signals for parallel memory banks. Use Value: Eliminates discrete NAND gate logic; reduces PCB area by 40% versus discrete decoder implementation. |
Use Scenario: Enabling specific UART, SPI, or ADC peripherals on a shared data bus in an industrial PLC backplane. IC Role / Device Role: Generates individual peripheral enable signals synchronized to address decode cycle. Use Value: Ensures mutually exclusive peripheral activation; prevents bus contention during multi-peripheral polling. |
| Digital Signal Routing | LED Segment Control |
|
Use Scenario: Directing sensor data streams from eight analog front-ends to a single ADC input channel in time-division multiplexing. IC Role / Device Role: Acts as a synchronous 1-of-8 analog switch controller using strobe inputs as clock-enable gates. Use Value: Achieves <13 ns channel switching latency; maintains signal integrity with matched trace lengths to Y0–Y7. |
Use Scenario: Driving common-anode 7-segment displays in a multi-digit panel meter with discrete digit selection. IC Role / Device Role: Supplies active-high digit-enable signals to PNP transistor bases controlling display anodes. Use Value: Delivers 4 mA per output - sufficient to saturate small-signal transistors without base resistors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CD74HC138E | Active-low outputs; identical pinout, timing, and supply specs | Requires external inverters to drive common-anode LEDs or active-high enables | Select when legacy designs use inverted output logic or require compatibility with existing '138-based layouts |
| SN74HC238N | Same function and pinout; manufactured by TI but with different internal process and qualification testing | No functional difference; RoHS-compliant with NIPDAU finish and identical PDIP packaging | Preferred for new designs requiring TI's latest production lot traceability and enhanced ESD robustness (4 kV HBM) |
Compared with CD74HC138E, the CD74HC238E eliminates external inversion for active-high loads, while SN74HC238N offers identical functionality with updated manufacturing controls and tighter parametric screening - both preserve full drop-in compatibility in PDIP-16 footprints.
Availability
CD74HC238E is available at Aetrix Electronics and suitable for memory address decoding, peripheral selection, digital signal routing, and LED segment control requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HC238E 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 global semiconductor leader delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The CD74HC238E belongs to TI's HC logic family, designed for high-speed, low-power, wide-voltage-range digital interfacing in harsh-environment embedded systems.
FAQ
What is the key functional difference between CD74HC238E and CD74HC138E?
The CD74HC238E provides active-high outputs (Y0–Y7 go high when selected), whereas the CD74HC138E provides active-low outputs (Y0–Y7 go low when selected). Both share identical pinout, enable structure (G2, G1, G0), timing specs, and supply range. This makes CD74HC238E ideal for driving common-anode LEDs or enabling active-high peripherals without external inverters.
Can CD74HC238E operate reliably at 3.3 V supply voltage?
Yes, CD74HC238E is fully specified for 2 V to 6 V operation. At VCC = 3.3 V, it maintains guaranteed VIH ≥ 2.0 V and VIL ≤ 1.0 V, supports 4 mA output drive, and delivers tpd ≤ 38 ns (CL = 50 pF). Its 30% noise margin ensures robust operation in mixed-voltage 3.3 V/5 V systems.
How does the enable logic work on CD74HC238E?
CD74HC238E requires G2 = high AND G1 = low AND G0 = low for normal decoding. If any enable condition fails - e.g., G2 = low, or G1 = high, or G0 = high - all outputs (Y0–Y7) are forced low. This three-input enable scheme allows precise hierarchical control in multi-device decode trees.
Is CD74HC238E pin-compatible with CD74HCT238E?
Yes, CD74HC238E and CD74HCT238E share identical PDIP-16 pinout, function table, and package dimensions. The difference lies in input threshold compatibility: CD74HCT238E accepts standard TTL input levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), while CD74HC238E uses CMOS thresholds (VIH ≥ 70% VCC). Both drive the same outputs.
What is the maximum output current per pin on CD74HC238E?
CD74HC238E supports ±4 mA DC output current per Y0–Y7 pin at VCC = 4.5 V, with VOL ≤ 0.4 V and VOH ≥ 3.7 V. Total device output current is limited to ±25 mA per pin and ±50 mA combined for VCC/GND paths. Exceeding these values risks parametric shift or latch-up.
CD74HC238E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
CD74HC238E FAQ
1.How can I place an order for CD74HC238E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HC238E 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 CD74HC238E reliable?
The price and inventory of CD74HC238E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HC238E is usually 5 days.
3.What payment methods are accepted for CD74HC238E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HC238E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HC238E?
CD74HC238E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HC238E 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 CD74HC238E?
For technical support, including CD74HC238E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HC238E requirements.
6.How does Aetrix verify that CD74HC238E is sourced from the original manufacturer or authorized distributors?
All CD74HC238E 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 CD74HC238E meets industry standards.
7.What is the process for return or replacement of CD74HC238E?
All CD74HC238E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HC238E, 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 CD74HC238E part is unused and in its original packaging.
Return procedure for CD74HC238E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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