Renesas 74LS148FP-E

Overview

74LS148FP-E from Renesas Electronics is an 8-line-to-3-line octal priority encoder IC with active-low inputs and outputs, cascading enable input (EI) and enable output (EO), group select (GS) flag, and TTL-compatible operation at 5 V. It encodes up to eight asynchronous low-active data lines into a 3-bit binary (4-2-1) output with priority resolution, supporting real-time interrupt request encoding in microcontroller systems. It operates across –20 °C to +75 °C and delivers propagation delays as low as 7 ns (t_PLH, EO).

For engineers reviewing the 74LS148FP-E datasheet, 74LS148FP-E pinout, 74LS148FP-E application, or 74LS148FP-E equivalent, this device is selected for deterministic priority encoding in industrial control panels, legacy bus arbitration logic, keyboard scan interfaces, and fault-signaling multiplexing where low-latency, fixed-function digital encoding without software overhead is required.

Technical Context

The 74LS148FP-E implements combinational priority encoding using standard TTL circuitry - no internal latches or clocks. Input priority order is fixed: line 7 (highest) > 6 > … > 0 (lowest), with all inputs and outputs asserted low. Cascading is supported via EI (active-low enable-in) and EO (active-low enable-out), allowing expansion to 16-, 24-, or more-line systems using multiple 74LS148FP-E units without external gates.

GS (Group Select) goes low when any input is active, indicating valid encoding; EO goes low only when EI is low *and* all inputs are inactive - enabling daisy-chained priority chaining. The device uses bipolar TTL technology, not CMOS, and requires a 5 V ±5% supply with typical ICC of 10 mA under operating conditions.

Key Specifications

Pinout & Package

SOP-16 package (JEITA code PRSP0016DH-B), 5.5 mm × 10.06 mm body, 1.27 mm pitch, Ni/Pd/Au-plated leads, mass 0.24 g.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar priority encoding applications.

Compared with SN74LS148N and MC14532B, the 74LS148FP-E provides identical logic functionality in a surface-mount package optimized for automated production, while maintaining full compatibility with existing 74LS system designs - making it the preferred choice for volume-manufactured industrial control boards requiring drop-in replacement of legacy DIP versions.

Availability

74LS148FP-E is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment, and keyboard interface modules requiring stable component supply and long-term obsolescence management.

Supply support for 74LS148FP-E 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

Renesas Electronics Corporation is a global semiconductor leader delivering microcontrollers, analog, power, and SoC solutions for industrial, automotive, and infrastructure markets.

The 74LS148FP-E belongs to Renesas' legacy TTL logic product line, designed specifically to support long-lifecycle industrial and instrumentation systems requiring pin- and function-compatible replacements for discontinued 74LS-series components.

FAQ

What is the logic polarity of inputs and outputs on the 74LS148FP-E?

The 74LS148FP-E uses active-low logic throughout: all eight data inputs (0–7), enable input (EI), group select (GS), enable output (EO), and the three-bit binary outputs (A2–A0) are asserted low. This matches standard TTL interrupt signaling and simplifies interfacing with open-collector sensors or mechanical switches without inversion logic.

Can the 74LS148FP-E be cascaded to handle more than eight inputs?

Yes - the 74LS148FP-E supports hardware cascading via EI and EO pins. To expand to 16 lines, connect EO of a higher-priority unit to EI of a lower-priority unit; GS of the top unit indicates overall activity. The 74LS148FP-E's built-in cascading eliminates external gates, preserving timing integrity and reducing board area.

What is the maximum fanout capability of the 74LS148FP-E outputs?

Each output of the 74LS148FP-E can sink up to 8 mA (I_OL), supporting a fanout of ≥10 standard 74LS inputs (each drawing ~0.4 mA). When driving heavier loads like LEDs or relays, external buffers or current-limiting resistors must be added - the 74LS148FP-E itself is not rated for direct relay coil drive.

Is the 74LS148FP-E RoHS compliant?

Yes - the 74LS148FP-E is manufactured by Renesas Electronics with lead-free terminations (Ni/Pd/Au plating) and complies with EU RoHS Directive 2011/65/EU. Full compliance documentation, including substance declarations and test reports, is available upon request from Aetrix Electronics for qualifying orders.

How does the Group Select (GS) signal behave during cascaded operation?

In cascaded configurations, GS of each 74LS148FP-E stage reflects *only its local inputs*. It does not aggregate across stages - so GS from the highest-priority unit must be OR'd (via wired-OR or external gate) with downstream GS signals to indicate overall system activity. This behavior ensures precise fault localization in multi-stage encoder systems.