Texas Instruments CD40109BF

Overview

CD40109BF from Texas Instruments is a quad low-to-high (and high-to-low) CMOS level-shifting buffer IC, designed for bidirectional voltage translation between incompatible logic domains. It operates with independent VCC (low-voltage) and VDD (high-voltage) supplies, supports unrestricted power-up sequencing, and delivers rail-to-rail output swing from –0.5 V to VDD + 0.5 V. It is used in mixed-supply microcontroller interfacing, legacy TTL-to-3.3V system bridging, and industrial control I/O isolation.

For engineers reviewing the CD40109BF datasheet, CD40109BF pinout, CD40109BF application, or CD40109BF equivalent, key selection considerations include its dual-supply independence, absence of power-sequence constraints, VCC > VDD high-to-low shifting capability, guaranteed input threshold at ≥0.7×VCC, and ceramic DIP-16 packaging for extended temperature and reliability-critical environments.

Technical Context

The CD40109BF implements four independent, non-inverting level-shifting channels using CMOS transmission-gate architecture with dual-threshold input stages. Each channel accepts inputs referenced to VSS and VCC, and outputs referenced to VSS and VDD - enabling true bidirectional level translation without external components or direction control signals.

It requires no external pull-ups or timing delays, tolerates VCC exceeding VDD (enabling high-to-low mode), and guarantees functional operation across –55°C to +125°C. Input signal swing must reach at least 0.7×VCC for reliable recognition, and output voltage range extends from –0.5 V to VDD + 0.5 V - supporting robust interface with analog or mixed-signal circuitry.

Key Specifications

Pinout & Package

Ceramic Dual-In-Line Package (CDIP-J), 16-pin, through-hole, hermetically sealed, with 0.3-inch body width and 0.1-inch lead pitch. Pin 1 marked by notch or bevel on top surface; leads are tin-lead (SNPB) finished.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar level-shifting applications.

Compared with CD40109BE and SN74LVC4245APWR, the CD40109BF uniquely combines ceramic hermetic packaging, –55°C to +125°C operation, rail-to-rail output including negative headroom, and unconditional power-sequence freedom - making it irreplaceable in mission-critical analog-digital boundary applications.

Availability

CD40109BF is available at Aetrix Electronics and suitable for industrial PLC design, aerospace avionics integration, and downhole oilfield instrumentation requiring stable component supply across extended product lifecycles.

Supply support for CD40109BF 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 high-reliability logic solutions with decades of heritage in military-qualified CMOS technology.

The CD40109B series was developed to solve mixed-voltage interface challenges in legacy-system upgrades and ruggedized electronics, emphasizing supply independence, wide temperature resilience, and minimal external component count.

FAQ

What is the maximum allowable voltage difference between VCC and VDD for CD40109BF?

The CD40109BF permits any relative magnitude between VCC and VDD within their individual absolute ratings (3 V to 18 V each), including VCC > VDD (enabling high-to-low shifting) or VDD > VCC (low-to-high). No differential limit is specified - only that both remain within 3–18 V and input swings meet ≥0.7×VCC. This flexibility is explicitly confirmed in the Harris/TI datasheet SCHS099B.

Does CD40109BF support negative input voltages?

No - the CD40109BF input structure is designed for signals swinging between VSS (ground) and at least 0.7×VCC. Inputs below VSS risk forward-biasing internal protection diodes and are outside absolute maximum ratings. The –0.5 V lower output limit applies only to outputs, not inputs.

Can CD40109BF be used in place of CD40109BE in an existing design?

Yes, electrically and functionally - the CD40109BF and CD40109BE share identical die and pinout. However, the CD40109BF uses a ceramic DIP package with SNPB leads and no RoHS compliance, whereas CD40109BE uses plastic DIP with NIPDAU and RoHS compliance. Mechanical fit is identical, but environmental and reliability profiles differ.

What is the purpose of pins 12–16 on CD40109BF?

Pins 12–16 on CD40109BF are unused and have no internal connection (NC). They are not reserved for test, configuration, or future functionality. Per the official TI datasheet SCHS099B and Package Addendum, these pins must remain unconnected in all applications - floating or tied to ground may cause parasitic coupling or violate layout guidelines.

Is CD40109BF compatible with modern 1.8 V or 2.5 V logic families?

Only when VCC is set to ≥3 V - the CD40109BF minimum VCC is 3 V per datasheet, and input threshold is defined as ≥0.7×VCC (i.e., ≥2.1 V at VCC = 3 V). Direct interfacing with 1.8 V or 2.5 V logic requires an intermediate buffer or level translator upstream of CD40109BF's inputs.