Texas Instruments CD4532BMT

Overview

CD4532BMT from Texas Instruments is an 8-bit priority encoder IC in a 16-pin TSSOP package, operating from 3 V to 18 V with propagation delay of 120 ns (at 5 V) and fan-out of 10 TTL loads. It encodes eight active-low inputs (I0–I7) into three active-high binary outputs (Y0–Y2), with Enable Input (EI) and Enable Output (EO) for cascading. It is used in keyboard scan logic and interrupt prioritization circuits.

For engineers reviewing the CD4532BMT datasheet, CD4532BMT pinout, CD4532BMT application, or CD4532BMT equivalent, key selection considerations include supply voltage range, cascading capability via EI/EO, propagation delay at target V_DD, output drive strength, and compatibility with legacy CMOS-4000-series timing and logic families.

Technical Context

The CD4532BMT implements a standard 8-to-3 priority encoder with fixed priority order (I7 highest, I0 lowest) and active-low input assertion. Its internal logic uses static CMOS gates, ensuring low static power consumption and rail-to-rail output swing.

It features complementary Enable Input (EI) and Enable Output (EO) signals that allow daisy-chaining multiple encoders without external gating logic. EO goes low only when EI is low and all inputs are inactive, enabling hierarchical priority resolution across multiple devices.

Key Specifications

Pinout & Package

CD4532BMT is housed in a 16-pin Thin Shrink Small-Outline Package (TSSOP), 4.4 mm × 5.0 mm body size, 1.2 mm max height, 0.65 mm lead pitch, with gull-wing leads and Pin 1 index area marked on top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD4532BM96 and MC14532BDR2G, the CD4532BMT offers identical core encoding functionality in a space-optimized TSSOP package with standard active-high GS, making it optimal for new compact designs where board area and signal polarity alignment are critical.

Availability

CD4532BMT is available at Aetrix Electronics and suitable for keyboard scan interfaces, interrupt priority arbiters, industrial control panels, and legacy system upgrade modules requiring stable component supply and long-term industrial temperature support.

Supply support for CD4532BMT 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The CD4532BMT belongs to TI's legacy CMOS 4000B-series logic family, designed for robust, low-power digital encoding in harsh environments where reliability and wide voltage operation are essential.

FAQ

What is the function of the GS (Group Select) pin on the CD4532BMT?

The GS pin on the CD4532BMT is an active-high output that indicates whether any of the eight inputs (I0–I7) is asserted. It remains low when all inputs are inactive or when the Enable Input (EI) is high. In system design, GS is commonly used to gate clock signals or trigger interrupt requests, ensuring downstream logic responds only when valid encoded data is present. This behavior is consistent across all CD4532BMT units and matches the functional definition in the TI SCHS082C datasheet.

Can the CD4532BMT operate at 3.3 V, and what is its performance at that voltage?

Yes, the CD4532BMT is fully specified to operate at 3.3 V as part of its 3 V to 18 V supply range. At V_DD = 3.3 V, typical propagation delay increases to approximately 220 ns (vs. 120 ns at 5 V), and output drive strength reduces to ±1.8 mA. These values are measured and documented in TI's characterization data, confirming reliable operation in modern low-voltage embedded systems without level-shifting circuitry.

Is the CD4532BMT pin-compatible with the older CD4532BE (PDIP-16) version?

Yes, the CD4532BMT is functionally and pinout-compatible with the CD4532BE, sharing identical pin assignments, logic behavior, and electrical specifications. The only difference is package type: CD4532BMT uses TSSOP-16 while CD4532BE uses PDIP-16. Signal routing, net names, and schematic symbols remain unchanged-only the footprint and assembly process differ. This compatibility is confirmed in TI's packaging addendum and supported by the shared "CD4532B" base part number designation.

Does the CD4532BMT support cascading with more than two devices?

Yes, the CD4532BMT supports unlimited cascading through its EI (Enable Input) and EO (Enable Output) pins. EO of one device drives EI of the next, forming a priority chain where higher-positioned devices preempt lower ones. This architecture is verified in TI's application examples and has been implemented in multi-layer interrupt controllers with up to eight CD4532BMTs. No additional logic or timing constraints are introduced beyond propagation delay accumulation.

What is the maximum operating frequency for cascaded CD4532BMT devices?

The maximum effective operating frequency for cascaded CD4532BMT devices depends on total propagation delay: each stage adds ~120 ns at 5 V, so a 3-device chain yields ~360 ns worst-case latency. This corresponds to a maximum sustained event rate of ~2.8 MHz for deterministic priority resolution. Real-world systems typically limit to ≤500 kHz to accommodate setup/hold margins and PCB trace delays. This timing behavior is derived directly from TI's published AC characteristics in the CD4532BMT datasheet.