Texas Instruments CD74HC109E

Overview

CD74HC109E from Texas Instruments is a dual positive-edge-triggered J-K flip-flop with asynchronous active-low set (1S, 2S) and reset (1R, 2R), operating from 2V to 6V supply. It delivers 54MHz maximum clock frequency at VCC = 5V with CL = 15pF, features Schmitt-trigger clock inputs for noise immunity, and supports industrial temperature range from –55°C to +125°C. It is used in synchronous logic control, state machines, and clock-domain synchronization circuits.

For engineers reviewing the CD74HC109E datasheet, CD74HC109E pinout, CD74HC109E application, or CD74HC109E equivalent, this page provides verified functional identity, validated pin roles, confirmed timing parameters across temperature, real-world noise immunity specs (NIL/NIH = 30% of VCC), and direct alternatives with documented functional and application-level differences.

Technical Context

The CD74HC109E implements two independent edge-triggered J-K flip-flops sharing no internal coupling-each with dedicated J, K, CP, S, R, Q, and Q̅ terminals. Its Schmitt-trigger clock inputs provide hysteresis (typ. 0.5V at VCC = 5V), enabling robust operation in noisy environments. The asynchronous set/reset override clock action and force outputs high when both S and R are low.

Propagation delays are tightly balanced: tPLH/tPHL from CP to Q is 14ns (typ.) at VCC = 5V, CL = 15pF; setup time tSU(J/K) is 18ns (max) and hold time tH is 5ns (max) over full temperature range. Input capacitance is fixed at 10pF, and power dissipation capacitance CPD is 30pF-key for dynamic power estimation in high-frequency toggle applications.

Key Specifications

Pinout & Package

CD74HC109E uses a 16-pin plastic dual in-line package (PDIP), with 0.3-inch body width and standard through-hole footprint. Pin 1 is located at top-left corner with notch orientation marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual J-K flip-flop applications.

Compared with CD74HC109E, CD74HCT109E trades supply flexibility for TTL compatibility, while SN74HC109N reduces temperature coverage to lower cost-making CD74HC109E the optimal choice for wide-voltage, extended-temp, noise-immune dual J-K applications.

Availability

CD74HC109E is available at Aetrix Electronics and suitable for industrial PLC sequencing, automotive body control modules, aerospace telemetry encoders, and test equipment pattern generators requiring stable component supply across extreme temperatures and long production lifecycles.

Supply support for CD74HC109E 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 logic solutions, with decades of heritage in high-reliability logic families.

The CD74HC109E belongs to TI's CD74HC high-speed CMOS logic series, designed for robust, low-power, wide-supply sequential logic in demanding industrial, aerospace, and automotive systems.

FAQ

What is the maximum clock frequency supported by CD74HC109E?

The CD74HC109E supports a maximum clock frequency of 54 MHz when operated at VCC = 5V with a 15 pF load and ambient temperature of 25°C. At full industrial temperature range (–55°C to +125°C), the guaranteed minimum fMAX is 23 MHz at VCC = 6V and 20 MHz at VCC = 4.5V, per TI's switching specifications table. These values are measured under defined test conditions including tr/tf = 6 ns and 50% duty cycle.

Does CD74HC109E have Schmitt-trigger inputs on all pins?

No-only the clock inputs (1CP and 2CP) feature Schmitt-trigger circuitry in the CD74HC109E. The J, K, S, and R inputs are standard CMOS inputs without hysteresis. This design ensures noise immunity on timing-critical clock edges while maintaining conventional logic thresholds on control and data inputs for predictable interface behavior with upstream logic.

Can CD74HC109E replace CD74HCT109E in an existing design?

CD74HC109E can replace CD74HCT109E only if the system operates within 2V–6V supply and all driving logic meets HC input thresholds (VIH ≥ 3.15V at VCC = 4.5V). It cannot directly interface with legacy 5V TTL outputs (which swing only to ~3.5V VOH) without level translation, since CD74HC109E requires VIH ≥ 3.15V, whereas CD74HCT109E accepts VIH ≥ 2.0V. Verify driver compatibility before substitution.

What happens when both set and reset are asserted low simultaneously on CD74HC109E?

When both S and R are low simultaneously on either flip-flop in the CD74HC109E, both Q and Q̅ outputs are forced high-a defined, stable condition per the truth table. However, if both S and R transition high at the same time, the resulting output state is unpredictable and unstable (as noted in the datasheet), and must be avoided in synchronous designs using proper reset sequencing or external arbitration.

Is CD74HC109E RoHS compliant and lead-free?

Yes, CD74HC109E is RoHS compliant and features a NiPdAu (nickel-palladium-gold) lead finish, as confirmed in TI's official packaging addendum. It is rated for lead-free soldering processes and carries "Yes" in the RoHS column for all active orderable variants (e.g., CD74HC109E and CD74HC109E.A), with MSL rating marked "N/A for Pkg Type" due to its PDIP through-hole construction.