CD4043 – Quad NOR R-S Latch with 3-State Outputs (CMOS Logic)

When your digital circuit needs a reliable way to capture, hold, and selectively transmit brief logic pulses or button presses, the CD4043 is the perfect solution. This integrated circuit contains four independent Reset-Set (R-S) latches constructed from cross-coupled NOR gates. When you apply a high signal to a latch's Set pin, its corresponding output goes high and stays high even after the Set signal is removed. Applying a high signal to the Reset pin forces the output back low. This fundamental memory action makes it ideal for switch debouncing, alarm event capture, and state retention in automated control systems.

What sets the CD4043 apart from basic logic gate arrays is its integrated Tri-State (or 3-state) output control. All four latches are connected to a common Enable pin. When the Enable pin is high, the latched memory states are passed directly to the output pins. However, when the Enable pin is pulled low, the outputs internally disconnect and enter a "high-impedance" state, essentially acting as if they are physically unplugged. This specialized feature allows you to safely connect the outputs of multiple CD4043 chips directly to a shared microcontroller data bus without causing short circuits or signal collisions.

Key Features & Functional Advantages

• Quad Memory Storage: Features four completely independent Set-Reset latches in a single package, allowing you to store four separate bits of hardware logic.

• Tri-State Outputs: The common Enable pin allows the chip to completely detach its outputs from the rest of your circuit, enabling safe connections to shared data lines and microcontrollers.

• Wide Voltage Compatibility: True to the CD4000 series heritage, it operates flawlessly across a wide supply range from 3 Volts to 15 Volts DC.

• High Noise Immunity: CMOS construction provides excellent resistance to electrical interference, making it highly reliable in industrial or electrically noisy environments.

• Active-High Logic: Designed specifically for positive logic systems; both the Set and Reset actions are triggered by high voltage signals.

Perfect For

• Hardware Switch Debouncing: The classic solution for cleaning up the noisy, bouncy electrical signals generated by mechanical pushbuttons and toggle switches before they reach a microcontroller.

• Alarm and Fault Logging: Excellent for capturing brief, fleeting fault signals from industrial sensors and holding them steady until a master controller can read and clear the latch.

• Shared Bus Architectures: Ideal for building custom memory registers or multi-sensor arrays that need to take turns transmitting data down a single set of wires.

• Basic State Machines: Useful for creating dedicated hardware logic sequences that do not require the overhead or power consumption of a full programmable microcontroller.

Technical Specifications

• Logic Family: CD4000 Series CMOS

• Function: Quad R-S Latch (NOR Gate Configuration)

• Output Type: 3-State (High, Low, and High-Impedance)

• Number of Latches: 4 Independent Channels

• Operating Voltage Range: 3.0 Volts to 15.0 Volts DC

• Package Type: 16-Pin Dual Inline Package (DIP)

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