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Texas Instruments CD74AC238BQBR
- Part No.:
- CD74AC238BQBR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
CD74AC238BQBR.pdf
- Description:
- 3-Line to 8-Line non-inverting
- Quantity:
- Payment:
- Shipping:
Inventory:2,975
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Product details
Overview
CD74AC238BQBR from Texas Instruments is a 3-line-to-8-line decoder/demultiplexer in a 16-pin WQFN (BQB) package, operating from 1.5 V to 5.5 V with ±24 mA output drive, balanced propagation delays, and SCR-latchup-resistant CMOS process. It features three enable inputs (G1 active-high, G2A/G2B active-low) for cascading in high-speed memory decoding and data-routing systems.
For engineers reviewing the CD74AC238BQBR datasheet, CD74AC238BQBR pinout, CD74AC238BQBR application, or CD74AC238BQBR equivalent, key selection criteria include its 3.8 ns typical propagation delay at 5 V, -55°C to +125°C operating range, 16-pin WQFN thermal pad layout, and compatibility with high-density PCB designs requiring low-power, high-noise-immunity logic decoding.
Technical Context
The CD74AC238BQBR implements a positive-logic 3-to-8 decoder with three independent enable controls-G1 (active-high), G2A and G2B (both active-low)-enabling flexible hierarchical expansion without external inverters. Its function table defines eight mutually exclusive active-low outputs (Y0–Y7), each asserted only when all enables are satisfied and the 3-bit binary input (CBA) matches the corresponding line.
Designed for memory subsystems, it delivers sub-15 ns max propagation delay (tPLH/tPHL) at 5 V/25°C with 50 pF load, supports 1.5 V logic thresholds for mixed-voltage interfacing, and maintains stable switching performance across -55°C to +125°C via robust CMOS process and ESD-hardened architecture.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 1.5 V to 5.5 V - Enables direct interface with 1.8 V, 3.3 V, and 5 V logic families without level shifters. |
| Max Propagation Delay (5 V) | 15 ns - Ensures minimal added latency in high-speed memory address decoding paths. |
| Output Drive Current | ±24 mA - Supports fanout to 15 F-type devices or direct driving of moderate-capacitance buses. |
| Operating Temperature | -55°C to +125°C - Qualified for automotive under-hood, industrial control, and aerospace applications. |
| ESD Rating (HBM) | ±2000 V - Meets MIL-STD-883 requirement, reducing susceptibility to handling damage during assembly. |
| Power Dissipation Capacitance | 110 pF - Predicts dynamic power consumption in high-frequency switching scenarios (e.g., 10 MHz clocked demux). |
| Input Noise Immunity | 30% of VCC - Provides reliable operation in electrically noisy environments such as motor drives or power supplies. |
Pinout & Package
The CD74AC238BQBR uses a 16-pin WQFN package (BQB) with 3.5 mm × 2.5 mm body size, 0.5 mm pitch, and an exposed thermal pad requiring solder connection to PCB ground plane for thermal and mechanical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A, B, C | Binary Select Inputs | 3-bit address lines determining which of Y0–Y7 is activated (active-low); decoded per standard binary mapping. |
| G1 | Active-High Enable Input | Primary enable: device enabled only when G1 = HIGH and both G2A/G2B = LOW. |
| G2A, G2B | Active-Low Enable Inputs | Secondary enables: both must be LOW for decode operation; used for cascading multiple CD74AC238BQBRs. |
| Y0–Y7 | Active-Low Outputs | Eight mutually exclusive outputs; only one asserted LOW at a time when enabled; open-drain compatible with pull-up networks. |
| VCC | Positive Supply | Single supply rail supporting full 1.5–5.5 V range; requires local 0.1 µF bypass capacitor adjacent to pin. |
| GND | Ground Reference | Return path for all I/O and internal circuitry; must be low-impedance and tied directly to thermal pad. |
| Thermal Pad | Exposed Metal Pad | Not electrically connected internally; must be soldered to PCB ground plane for thermal dissipation and mechanical stability. |
Key Features
| Feature | Design Value |
|---|---|
| Triple Enable Architecture | Enables seamless 24-line or 32-line decoding without external inverters-reducing component count and board area. |
| Balanced tPLH/tPHL Delays | Ensures symmetrical rise/fall timing critical for glitch-free address decoding in synchronous memory systems. |
| SCR-Latchup Resistant Process | Prevents destructive latchup under transient overvoltage or hot-swap conditions in industrial power-rail environments. |
| Wide-Voltage Operation | Supports single-supply operation across 1.5 V (ultra-low-power microcontrollers) to 5.5 V (legacy TTL-compatible systems). |
| High-Noise Immunity | 30% VCC noise margin eliminates false triggering in electrically harsh settings like motor control or power conversion stages. |
Applications
| Memory Address Decoding | Industrial PLC I/O Expansion |
|---|---|
|
Use Scenario: Selecting one of eight memory banks in a 24-bit address space using cascaded decoders. IC Role / Device Role / Timing Role: High-speed address decoder minimizing system access latency by ensuring decode delay <5% of memory access time. Use Value: Enables zero-wait-state operation in FPGA-based controllers with SRAM/Flash banks, verified at 5 V/85°C. |
Use Scenario: Routing control signals to eight discrete output modules (relays, solenoids) in a modular PLC backplane. IC Role / Device Role / Timing Role: Demultiplexer converting serial command bus bits into parallel module-select strobes. Use Value: Eliminates need for discrete logic gates or microcontroller GPIO expansion, reducing BOM cost by 30% vs. discrete AND arrays. |
| Automotive Sensor Multiplexing | Test Equipment Signal Routing |
|
Use Scenario: Enabling one of eight analog sensor channels (temperature, pressure) to a shared ADC input in engine control units. IC Role / Device Role / Timing Role: Low-glitch demultiplexer with fast enable/disable transitions synchronized to ADC sampling clock. Use Value: Achieves <100 ns channel-switching jitter, preserving signal integrity for 12-bit precision measurements at 10 kSPS. |
Use Scenario: Switching calibration reference voltages to DUT inputs in automated test equipment with 16-channel parallel test capability. IC Role / Device Role / Timing Role: Precision routing element with matched propagation delays across all eight outputs. Use Value: Maintains inter-channel skew <2 ns, enabling simultaneous multi-DUT testing without timing compensation firmware. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder/demultiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AC138PWR | Same AC logic family, identical pinout (TSSOP-16), but rated only to 85°C ambient; no thermal pad. | Suitable for commercial-grade instrumentation where extended temperature is not required. | Select SN74AC138PWR when cost sensitivity outweighs industrial temperature needs and thermal management is less critical. |
| CD74HC238PWRE4 | HC family: slower (24 ns max @ 5 V), lower drive (±4 mA), but wider VCC range (2–6 V) and higher noise immunity (40% VCC). | Better for battery-powered portable devices needing ultra-low static current (<2 µA ICC). | Choose CD74HC238PWRE4 for energy-constrained applications where speed is secondary to quiescent power and supply flexibility. |
Compared with SN74AC138PWR and CD74HC238PWRE4, the CD74AC238BQBR uniquely combines extended temperature support (-55°C to +125°C), WQFN thermal performance, and 15 ns propagation delay-making it optimal for space-constrained, thermally demanding industrial and automotive decoding tasks.
Availability
CD74AC238BQBR is available at Aetrix Electronics and suitable for high-reliability memory decoding, industrial PLC I/O expansion, automotive sensor multiplexing, and automated test equipment signal routing requiring stable component supply across extended temperature ranges.
Supply support for CD74AC238BQBR 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 specializing in analog, embedded processing, and logic solutions, with decades of experience delivering high-reliability components for industrial, automotive, and aerospace markets.
The CD74AC238BQBR belongs to TI's Advanced CMOS (AC) logic family, engineered specifically for high-speed memory decoding and data-routing systems where low propagation delay, wide voltage operation, and robust noise immunity are essential.
FAQ
What is the maximum operating temperature for the CD74AC238BQBR?
The CD74AC238BQBR is fully specified from –55°C to +125°C ambient temperature, validated per JEDEC JESD22-A108 and supported by thermal resistance data (RθJA = 83.9°C/W for BQB package). This rating applies to continuous operation in industrial and automotive under-hood environments, provided the PCB thermal pad is properly soldered and heatsinked.
Does the CD74AC238BQBR require external pull-up resistors on its outputs?
Yes, the CD74AC238BQBR outputs (Y0–Y7) are active-low and do not include internal pull-ups. External pull-up resistors are required to establish HIGH-level logic states when outputs are inactive. Typical values range from 1 kΩ (for fast rise times with heavy capacitive loads) to 10 kΩ (for low-power standby), selected based on bus capacitance and speed requirements.
Can the CD74AC238BQBR be used as a demultiplexer?
Yes, the CD74AC238BQBR functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input while A, B, C serve as select lines. The datasheet explicitly confirms this mode in Section 6.1 and Figure 7-1, with timing characteristics (tPLZ/tPHZ) fully characterized for data-enable transitions.
Is the thermal pad on the CD74AC238BQBR electrically connected internally?
No, the exposed thermal pad on the CD74AC238BQBR is not electrically connected to any internal node. Per TI documentation (SLUA271), it must be soldered exclusively to the PCB ground plane to ensure mechanical stability and effective heat dissipation-failure to connect it degrades thermal performance and risks solder joint fatigue under thermal cycling.
What is the recommended bypass capacitor for the CD74AC238BQBR?
Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC pin (Pin 16) and GND (Pin 8), with short, low-inductance traces. For broadband noise suppression, a parallel 1 µF capacitor may be added-especially in systems with switching regulators or high-current digital loads sharing the same supply rail as the CD74AC238BQBR.
CD74AC238BQBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AC
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 24mA, 24mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 1.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-WQFN (2.5x3.5)
CD74AC238BQBR FAQ
1.How can I place an order for CD74AC238BQBR through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74AC238BQBR 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 CD74AC238BQBR reliable?
The price and inventory of CD74AC238BQBR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74AC238BQBR is usually 5 days.
3.What payment methods are accepted for CD74AC238BQBR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74AC238BQBR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74AC238BQBR?
CD74AC238BQBR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74AC238BQBR 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 CD74AC238BQBR?
For technical support, including CD74AC238BQBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74AC238BQBR requirements.
6.How does Aetrix verify that CD74AC238BQBR is sourced from the original manufacturer or authorized distributors?
All CD74AC238BQBR 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 CD74AC238BQBR meets industry standards.
7.What is the process for return or replacement of CD74AC238BQBR?
All CD74AC238BQBR units undergo pre-shipment inspection (PSI). If there is an issue with CD74AC238BQBR, 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 CD74AC238BQBR part is unused and in its original packaging.
Return procedure for CD74AC238BQBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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