Texas Instruments NE556NS

Overview

NE556NS from Texas Instruments is a dual precision timer IC containing two independent 555-type timing circuits in a single 14-pin SOP (NS) package. It supports both astable and monostable operation with TTL-compatible outputs capable of sinking or sourcing up to 150 mA, threshold/trigger levels at 2/3 VCC and 1/3 VCC respectively, and operates across 0°C to 70°C. It is used in pulse-width modulation, missing-pulse detection, and sequential timing control for industrial instrumentation.

For engineers reviewing the NE556NS datasheet, NE556NS pinout, NE556NS application, or NE556NS equivalent, key selection considerations include its dual-timer architecture, ±200 mA output drive capability, 1.5% typical timing error at 25°C, temperature coefficient of 90 ppm/°C (astable), and compatibility with legacy NE555-based designs requiring compact dual-channel timing.

Technical Context

The NE556NS integrates two independent bipolar 555-style timers sharing only VCC and GND. Each timer features a voltage divider setting fixed 1/3 and 2/3 VCC thresholds, an SR flip-flop, discharge transistor, and push-pull output stage. The CONT pin allows active bias modulation of internal comparators for precision timing adjustment.

Reset input overrides trigger and threshold inputs, forcing output low and enabling discharge switch conduction. Trigger falling below 1/3 VCC sets the flip-flop; threshold rising above 2/3 VCC resets it. Output state directly controls DISCH–GND path impedance - low-impedance when output is low, high-impedance otherwise.

Key Specifications

Pinout & Package

NE556NS uses a 14-pin SOP (Small Outline Package) with 1.27 mm pitch, 8.65 mm × 3.9 mm body, and gull-wing leads. Pin 1 is marked by a notch or dot; device is RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual precision timer applications.

Compared with NE556NS, NE556N offers mechanical robustness and ease of hand-soldering but larger board area, while NE556DR provides superior thermal performance and industry-standard SOIC compatibility - all three share identical timing behavior, pinout, and electrical interface.

Availability

NE556NS is available at Aetrix Electronics and suitable for industrial controls, touch-tone encoders, and pulse-position modulation systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for NE556NS 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and consumer reach.

The NE556NS belongs to TI's legacy precision timer product line, designed specifically for analog timing applications where reliability, wide supply range, and direct drive capability supersede digital programmability.

FAQ

What is the maximum supply voltage for NE556NS?

The absolute maximum supply voltage for NE556NS is 18 V, but the recommended operating range is 4.5 V to 16 V per TI's SLFS023G datasheet. Operating above 16 V risks exceeding internal junction temperature limits and degrading long-term reliability. The NE556NS maintains full functionality and specified timing accuracy within the 4.5–16 V window, making it compatible with standard 5 V and 12 V systems.

Does NE556NS support both astable and monostable modes?

Yes, NE556NS supports both astable (free-running oscillator) and monostable (one-shot) operation per timer section. Each half functions identically to a standalone NE555, using external resistors and capacitors to set timing intervals. The datasheet confirms this in the Functional Block Diagram and Application Information sections, with Figures 1 and 2 explicitly illustrating astable and monostable configurations for the NE556NS.

What is the timing accuracy of NE556NS at room temperature?

At TA = 25°C, NE556NS exhibits a typical timing interval error of 1.5% in astable mode and 3% in monostable mode, as specified in the Operating Characteristics table of the SLFS023G datasheet. This accuracy holds for standard RC values (e.g., RA = 1 kΩ–100 kΩ, C = 0.1 µF) and reflects manufacturing process variation - not temperature or supply drift.

Can NE556NS drive a 12 V relay directly?

Yes, NE556NS can drive a 12 V relay coil directly when configured in open-collector mode with an external pull-up to 12 V, or in push-pull mode if the relay coil draws ≤200 mA. Its output sinks up to 200 mA at VCC = 12 V with VOL ≤ 0.75 V (typical), satisfying most 12 V relay dropout requirements. Always verify coil resistance and ensure power dissipation stays within NE556NS's 800 mW limit.

Is NE556NS pin-compatible with NE555-based designs?

No - NE556NS is not pin-compatible with a single NE555, as it contains two complete timers in one 14-pin package. However, it is functionally and footprint-compatible with other NE556 variants (NE556N, NE556DR) and serves as a drop-in replacement for dual-555 discrete layouts. Its pinout matches the industry-standard dual-timer arrangement defined in TI's SLFS023G, ensuring direct substitution in existing NE556 designs.