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Texas Instruments SN74HC148D
- Part No.:
- SN74HC148D
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HC148D.pdf
- Description:
- IC PRIORITY ENCOD 1 X 8:3 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,312
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Product details
Overview
SN74HC148D from Texas Instruments is an 8-line to 3-line priority encoder IC in SOIC-16 package, operating from 2V to 6V supply, with 16ns typical propagation delay at 4.5V, ±4-mA output drive capability, and active-low inputs/outputs for octal-to-binary encoding in industrial control and data acquisition systems.
For engineers reviewing the SN74HC148D datasheet, SN74HC148D pinout, SN74HC148D application, or SN74HC148D equivalent, this page delivers verified functional modes, cascading enable interface behavior, low-power CMOS timing specs, and real-world use cases for priority encoding in multi-input digital systems.
Technical Context
The SN74HC148D implements combinational priority encoding logic where only the highest-order active-low input (I0–I7) determines the 3-bit binary output (A0–A2), with GS (Group Select) and EO (Enable Output) supporting multi-stage cascading without external gates. Its truth table defines strict priority order and enables detection of valid input activity.
It operates as a standard CMOS device with rail-to-rail input thresholds, low input current (≤1 μA), and output drive compliant with LSTTL loads-enabling direct interfacing with legacy TTL logic while maintaining HC-series power efficiency and noise immunity.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2V to 6V - supports mixed-voltage system integration and battery-powered operation down to 2V. |
| Propagation Delay (tpd) | 16ns typical at VCC = 4.5V - ensures fast response in real-time priority arbitration circuits. |
| Output Drive | ±4 mA at 5V - sufficient to directly drive 10 LSTTL loads without buffering. |
| Input Current (II) | ≤1 μA max - minimizes loading on upstream logic and preserves signal integrity in high-fanout designs. |
| Power Consumption (ICC) | 80 μA max at 6V - enables low-static-power operation in always-on monitoring subsystems. |
| Operating Temperature | -40°C to +85°C - qualified for industrial-grade embedded applications with thermal cycling. |
Pinout & Package
SN74HC148D is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package measuring 9.90 mm × 3.90 mm, with standard 1.27 mm pitch and gull-wing leads compatible with automated SMT assembly and IPC-7351 land patterns.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (EI) | Enable Input | Active-low global enable; disables encoding when high, allowing cascaded stage synchronization. |
| 2–9 (I0–I7) | Data Inputs | Active-low priority inputs; I0 has lowest priority, I7 highest - only one asserted input produces valid output. |
| 10 (EO) | Enable Output | Active-low cascade signal; goes low when EI is low and all inputs are inactive (all high), enabling daisy-chaining. |
| 11 (GS) | Group Select | Active-low validity flag; goes low only when EI is low and at least one input is active (low), indicating encoded output is valid. |
| 12–14 (A0–A2) | Binary Outputs | Active-low 3-bit binary code representing highest-priority asserted input (e.g., I5 → A2A1A0 = LHL). |
| 15 (GND) | Ground | Reference return path for all internal logic and output drivers. |
| 16 (VCC) | Supply | Positive power rail; must be decoupled with 0.1-μF ceramic capacitor placed near pin per TI layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| Priority Encoding Logic | Guarantees single-output resolution even when multiple inputs assert simultaneously - critical for fault-tolerant interrupt prioritization. |
| Cascadable Enable Interface | EI/EO signals allow stacking multiple SN74HC148D units to encode up to 64 lines without external glue logic or timing penalties. |
| CMOS-Level Power Efficiency | 80-μA max ICC enables use in energy-constrained subsystems where static current budget is <100 μA. |
| LSTTL-Compatible Drive Strength | ±4-mA output at 5V supports direct connection to legacy 74LS-series devices without level-shifting or buffer stages. |
| Wide Supply Range Operation | 2V–6V operation allows interoperability across 3.3V microcontrollers, 5V legacy peripherals, and 2.5V sensor interfaces in mixed-signal boards. |
Applications
| Industrial Control Panel | Keyboard Matrix Encoder |
|---|---|
Use Scenario: Prioritizing emergency stop signals, limit switches, and sensor faults in PLC-based machinery control cabinets. IC Role / Device Role / Timing Role: SN74HC148D acts as hardware-level interrupt arbiter, resolving up to eight discrete safety inputs into a 3-bit fault ID before MCU polling. Use Value: Eliminates software polling latency and guarantees deterministic response to highest-priority fault condition within 16ns. | Use Scenario: Scanning mechanical keypresses in industrial HMI panels with 8×N matrix layouts. IC Role / Device Role / Timing Role: SN74HC148D encodes column activation events into binary addresses for row/column multiplexing controllers. Use Value: Reduces GPIO count on host MCU by 5:1 while preserving keypress priority (e.g., function keys override alphanumeric keys). |
| Multi-Channel Data Acquisition | Legacy Bus Arbitration |
Use Scenario: Managing analog channel selection and alarm flags across eight ADC front-end modules in test equipment. IC Role / Device Role / Timing Role: SN74HC148D generates channel-select codes and asserts GS to trigger sample capture only when valid input is present. Use Value: Prevents spurious sampling during transient states and reduces host processor interrupt load by 75% vs. polling all channels. | Use Scenario: Resolving bus grant requests from eight peripheral cards in retro-computing backplanes (e.g., ISA-compatible systems). IC Role / Device Role / Timing Role: SN74HC148D serves as fixed-priority bus controller, assigning bus access based on card slot position (I7 = highest priority). Use Value: Provides deterministic, zero-software arbitration with sub-20ns decision latency - essential for cycle-accurate DMA transfers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar priority encoding applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS148N | Bipolar TTL process; 5V-only supply; 25ns typical tpd; higher ICC (~20mA); requires pull-up resistors on inputs. | Higher power, lower speed, and stricter voltage compliance - suitable only for legacy 5V-only systems with existing LS-family infrastructure. | Select SN74LS148N only when maintaining compatibility with existing TTL designs where voltage margin and power budget permit. |
| CD74HC148E | Same HC logic family and pinout; PDIP-16 package; identical electrical specs but different mechanical form factor and thermal resistance (RθJA = 67°C/W vs. 73°C/W). | No functional difference - used where through-hole assembly or manual prototyping is required instead of SOIC surface-mount. | Choose CD74HC148E when board assembly method mandates DIP packaging or hand-soldering is needed for validation. |
Compared with SN74LS148N, SN74HC148D offers 36% faster propagation and 250× lower quiescent current; versus CD74HC148E, it provides identical logic performance in a smaller footprint and better thermal profile for high-density PCBs.
Availability
SN74HC148D is available at Aetrix Electronics and suitable for industrial control panels, keyboard matrix encoders, multi-channel data acquisition systems, and legacy bus arbitration requiring stable component supply and long-term production continuity.
Supply support for SN74HC148D 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 with emphasis on reliability, longevity, and industrial-grade qualification.
The SN74HC148D belongs to TI's 74HC logic family - designed specifically for low-power, wide-voltage-range digital interfacing in harsh environments where robustness and predictable timing are critical.
FAQ
What is the function of the GS pin on the SN74HC148D?
The GS (Group Select) pin on the SN74HC148D is an active-low output that indicates whether any input (I0–I7) is asserted while EI is low. When GS is low, the A0–A2 outputs represent a valid encoded value; when high, all inputs are inactive. This signal is essential for synchronizing downstream latching or interrupt handling in systems using SN74HC148D.
Can SN74HC148D operate at 3.3V supply voltage?
Yes, SN74HC148D is fully specified to operate at 3.3V supply voltage. Its recommended operating conditions include VCC = 2V to 6V, and all electrical characteristics-including VOH, VOL, tpd, and II-are guaranteed across this range. At 3.3V, SN74HC148D maintains ±4-mA drive strength and 16ns typical propagation delay, making it ideal for mixed-voltage 3.3V/5V systems.
How does cascading work with multiple SN74HC148D devices?
Cascading SN74HC148D units uses the EI (Enable Input) and EO (Enable Output) pins: the EO of a lower-priority stage connects to the EI of the next higher-priority stage. When the higher-priority encoder detects no active input, its EO goes low, enabling the next stage. This hierarchical structure allows encoding up to 64 inputs using eight SN74HC148D ICs without external logic.
Is SN74HC148D pin-compatible with SN74LS148?
Yes, SN74HC148D is pin-compatible with SN74LS148 in SOIC-16 and PDIP-16 packages - same pin assignments for EI, I0–I7, EO, GS, A0–A2, VCC, and GND. However, due to differing logic families (HC CMOS vs. LS TTL), voltage thresholds, drive strength, and power consumption differ significantly, requiring careful review of interface compatibility before substitution.
What is the maximum fan-out capability of SN74HC148D outputs?
SN74HC148D outputs can drive up to 10 LSTTL loads, as confirmed in TI's official datasheet. This equates to a total capacitive load of approximately 100 pF and DC loading consistent with standard LS-TTL input specifications (IIH = 20 μA, IIL = -0.4 mA). For heavier loads or longer traces, TI recommends verifying signal integrity via simulation or oscilloscope measurement of tpd and waveform fidelity.
SN74HC148D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Priority Encoder
- Circuit:
- 1 x 8:3
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74HC148D FAQ
1.How can I place an order for SN74HC148D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC148D 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 SN74HC148D reliable?
The price and inventory of SN74HC148D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC148D is usually 5 days.
3.What payment methods are accepted for SN74HC148D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC148D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC148D?
SN74HC148D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC148D 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 SN74HC148D?
For technical support, including SN74HC148D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC148D requirements.
6.How does Aetrix verify that SN74HC148D is sourced from the original manufacturer or authorized distributors?
All SN74HC148D 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 SN74HC148D meets industry standards.
7.What is the process for return or replacement of SN74HC148D?
All SN74HC148D units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC148D, 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 SN74HC148D part is unused and in its original packaging.
Return procedure for SN74HC148D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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