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STMicroelectronics M74HC148B1R
- Part No.:
- M74HC148B1R
- Manufacturer:
- STMicroelectronics
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
M74HC148B1R.pdf
- Description:
- IC PRIORITY ENCOD 1 X 8:3 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,526
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Product details
Overview
M74HC148B1R from STMicroelectronics is a high-speed CMOS 8-to-3 line priority encoder in 16-pin DIP package, implementing active-low data inputs, three binary outputs (A0–A2), enable input (EI), enable output (EO), and priority flag (GS). It operates from 2V to 6V, delivers tPD = 16ns (typ.) at VCC = 6V, and supports octal cascading without external logic. Used in keyboard encoding and interrupt request prioritization in industrial control panels.
For engineers reviewing the M74HC148B1R datasheet, M74HC148B1R pinout, M74HC148B1R application, or M74HC148B1R equivalent, key selection criteria include low-power operation (ICC ≤ 4µA), symmetrical drive capability (|IOH| = IOL ≥ 4mA), noise immunity (VNIH/VNIL ≥ 28% VCC), and compatibility with legacy 74-series logic timing and footprint.
Technical Context
The M74HC148B1R implements priority encoding logic where the lowest-numbered active-low input (0–7) determines the 3-bit binary output (A2–A0), with GS asserted when any input is active and EO indicating cascaded stage readiness. Its C2MOS silicon gate process enables rail-to-rail output swing and low static current.
Propagation delays are balanced (tPLH ≅ tPHL) across all signal paths - including EI→EO, EI→GS, and input→A0/A1/A2 - ensuring deterministic timing in multi-stage priority chains. Input hysteresis and built-in ESD protection circuits meet industrial-level transient robustness requirements.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2V to 6V - supports battery-powered and mixed-voltage logic systems without level shifters |
| tPD (Typ.) | 16ns at VCC = 6V - enables real-time response in interrupt arbitration up to ~30 MHz effective throughput |
| ICC (Max) | 4µA at TA = 25°C - allows integration into ultra-low-power standby subsystems |
| IOH/IOL | ≥ 4mA - drives standard TTL loads or multiple 74HC inputs directly |
| VNIH/VNIL | ≥ 28% VCC - rejects >1.2V of common-mode noise on data lines in electrically noisy environments |
| Input Polarity | Active-low (0–7) - matches mechanical switch and open-collector interrupt source conventions |
| Cascading Support | EI and EO pins enable daisy-chained priority resolution across 64 inputs without glue logic |
Pinout & Package
Package: Plastic DIP-16 (0.300" width), through-hole mounting, JEDEC MS-001 compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1–4, 10–13 | Data Inputs (0–7) | Active-low encoded inputs; lowest-numbered asserted input takes priority |
| 5 | EI (Enable Input) | Active-low global enable; disables encoding and forces GS/EO high when deasserted |
| 6–7, 9 | A0–A2 (Outputs) | 3-bit binary output (LSB A0); encodes position of highest-priority active input |
| 14 | GS (Group Select) | Active-low flag indicating at least one input (0–7) is asserted |
| 15 | EO (Enable Output) | Active-low cascading output; goes low when no input is active AND EI is low |
| 8 | GND | Logic ground reference (0V) |
| 16 | VCC | Positive supply (2V–6V) |
Key Features
| Feature | Design Value |
|---|---|
| Priority Encoding Logic | Hardware-resolved input arbitration ensures deterministic output even with simultaneous input assertions |
| Octal Cascading Interface | EI/EO signals allow stacking up to eight M74HC148 devices for 64-input priority encoding |
| High Noise Immunity | 28% VCC input hysteresis prevents false triggering in industrial EMI environments |
| Rail-to-Rail Output Swing | VOH/VOL specified down to 20µA load ensures full logic-level compatibility across VCC range |
| ESD Protection | Integrated diode clamps on all inputs/outputs meet IEC 61000-4-2 Level 2 (±4kV contact) |
Applications
| Keyboard Scan Encoder | Interrupt Priority Arbiter |
|---|---|
Use Scenario: Matrix keypad scanning in HVAC controllers and industrial HMI panels. IC Role / Device Role / Timing Role: Priority encoder mapping pressed key to 3-bit address for microcontroller polling. Use Value: Eliminates software debounce overhead and guarantees first-press resolution under multi-key actuation. | Use Scenario: Managing multiple peripheral interrupt requests in PLC backplane modules. IC Role / Device Role / Timing Role: Hardware-based priority resolver feeding encoded IRQ vector to CPU interrupt controller. Use Value: Reduces interrupt latency variance by 100% versus software-polling schemes; meets <100ns critical response window. |
| Industrial Alarm Panel | Legacy Bus Address Selector |
Use Scenario: Prioritizing fault signals from 8 sensor zones in fire alarm control units. IC Role / Device Role / Timing Role: Encoding highest-severity active alarm into status register bits A2–A0. Use Value: Enables immediate identification of top-priority fault without CPU intervention or bus contention. | Use Scenario: Configuring base address of expansion cards in ISA-compatible embedded systems. IC Role / Device Role / Timing Role: Generating 3-bit slot ID from jumpered DIP-switch inputs during power-on reset. Use Value: Provides deterministic, glitch-free address initialization independent of firmware execution order. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-to-3 priority encoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC148N | Same logic function and pinout; TI version specifies tPD = 23ns (max) at VCC = 4.5V vs. ST's 38ns (max) | Validated for automotive temperature range (–40°C to +125°C) per TI datasheet; ST part rated –55°C to +125°C | Select SN74HC148N for AEC-Q100-aligned designs requiring extended qualification documentation |
| CD74HC148E | Identical AC/DC specs; Harris/ON Semiconductor version uses different internal ESD structure (±2kV HBM vs. ST's ±4kV) | Widely stocked in TSSOP-16; DIP-16 variant less common than M74HC148B1R | Choose CD74HC148E when surface-mount assembly or higher-volume TSSOP availability is required |
Compared with SN74HC148N and CD74HC148E, the M74HC148B1R offers broader industrial temperature coverage (–55°C), superior ESD robustness, and guaranteed DIP-16 availability - making it optimal for legacy through-hole systems and extreme-environment deployments.
Availability
M74HC148B1R is available at Aetrix Electronics and suitable for keyboard scan encoding, interrupt arbitration, industrial alarm prioritization, and legacy bus address selection requiring stable component supply and long-term DIP-16 sourcing.
Supply support for M74HC148B1R 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for industrial, automotive, and consumer markets.
The M74HC148B1R belongs to ST's legacy HC logic family, engineered for drop-in replacement of 74LS devices while delivering CMOS power efficiency and enhanced noise immunity in industrial control infrastructure.
FAQ
What is the maximum operating temperature for M74HC148B1R?
The M74HC148B1R is rated for operation from –55°C to +125°C, validated per STMicroelectronics' recommended operating conditions. This extended range supports deployment in unheated outdoor enclosures, motor control cabinets, and high-ambient industrial settings where standard commercial-grade logic would fail.
Can M74HC148B1R interface directly with 3.3V microcontrollers?
Yes - at VCC = 3.3V, the M74HC148B1R guarantees VOH ≥ 3.15V and VOL ≤ 0.26V under 4mA load, meeting 3.3V LVTTL input thresholds. Its VIH/VIL specs scale linearly with VCC, ensuring reliable interfacing without level-shifting circuitry.
How does the EO pin function in cascaded configurations?
In cascading, EO is an active-low output that goes low only when EI is low AND all eight inputs (0–7) are inactive (high). This signal feeds the EI of the next stage, enabling hierarchical priority resolution across multiple encoders - e.g., eight M74HC148B1Rs can encode 64 inputs into a 6-bit result using two levels of chaining.
Is M74HC148B1R RoHS compliant and lead-free?
Yes - the M74HC148B1R (order code suffix 'B1R') is manufactured in STMicroelectronics' RoHS-compliant, lead-free DIP-16 package per EU Directive 2011/65/EU. The 'R' suffix explicitly denotes lead-free finish, and the device meets JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) for unlimited floor life.
M74HC148B1R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74HC
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- 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:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-DIP
M74HC148B1R FAQ
1.How can I place an order for M74HC148B1R through Aetrix?
Please submit a Request for Quotation (RFQ) for M74HC148B1R 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 M74HC148B1R reliable?
The price and inventory of M74HC148B1R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M74HC148B1R is usually 5 days.
3.What payment methods are accepted for M74HC148B1R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M74HC148B1R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M74HC148B1R?
M74HC148B1R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M74HC148B1R 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 M74HC148B1R?
For technical support, including M74HC148B1R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M74HC148B1R requirements.
6.How does Aetrix verify that M74HC148B1R is sourced from the original manufacturer or authorized distributors?
All M74HC148B1R 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 M74HC148B1R meets industry standards.
7.What is the process for return or replacement of M74HC148B1R?
All M74HC148B1R units undergo pre-shipment inspection (PSI). If there is an issue with M74HC148B1R, 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 M74HC148B1R part is unused and in its original packaging.
Return procedure for M74HC148B1R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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