Texas Instruments NA556D

Overview

NA556D from Texas Instruments is a dual precision timer IC integrating two independent 555-type timing circuits in a single SOIC-14 package, operating from –40°C to +105°C with supply voltage range 4.5 V to 16 V, TTL-compatible outputs capable of ±200 mA sink/source, and precise threshold/trigger levels at ≈1/3 and ≈2/3 V_CC. It supports astable and monostable operation for industrial control, pulse-width modulation, and missing-pulse detection.

For engineers reviewing the NA556D datasheet, NA556D pinout, NA556D application, or NA556D equivalent, this page delivers verified electrical characteristics, validated dual-timer functional behavior, confirmed SOIC-14 package mapping, exact pin functions per TI SLFS023I (March 2025), and real-world design implications for timing stability, reset override hierarchy, and RC-based interval accuracy.

Technical Context

The NA556D implements two fully independent 555-style timers sharing only V_CC and GND. Each timer features a resistor-divider–based threshold comparator (≈2/3 V_CC), trigger comparator (≈1/3 V_CC), SR latch, output driver, and open-collector discharge switch - all internally biased and temperature-compensated. The CONT pin allows active modulation of both thresholds simultaneously.

Reset input has highest priority, overriding TRIG and THRES; TRIG overrides THRES when CONT = 2/3 V_CC. Timing intervals are supply-voltage–independent due to proportional scaling of thresholds and charge rates, with typical temperature coefficient of 50 ppm/°C (monostable) and 150 ppm/°C (astable) across –40°C to +105°C.

Key Specifications

Pinout & Package

NA556D is packaged in a 14-pin SOIC (Small Outline Integrated Circuit) with standard 1.27 mm pitch, JEDEC MS-012AC compliant, RoHS-compliant NIPDAU lead finish, and moisture sensitivity level (MSL) 1 (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with NA556D, NE556DR trades industrial temperature range for marginally higher supply tolerance, while SA556N retains full industrial temp rating but sacrifices surface-mount compatibility and thermal performance - making NA556D the optimal choice for modern SMT-based industrial controls requiring extended temperature operation and compact packaging.

Availability

NA556D is available at Aetrix Electronics and suitable for industrial control timers, pulse-width modulators, missing-pulse detectors, and sequential timing circuits requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for NA556D 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 digital signal technologies, with decades of leadership in precision timing and industrial-grade ICs.

The NA556D belongs to TI's legacy dual-timer product line designed specifically for robust, RC-based timing in industrial, instrumentation, and control systems where reliability across temperature and supply variation is critical.

FAQ

What is the maximum supply voltage for NA556D?

The NA556D has an absolute maximum supply voltage of 18 V, but its recommended operating range is 4.5 V to 16 V per TI SLFS023I (March 2025). Operation above 16 V risks exceeding safe junction temperature or violating recommended conditions, even though 18 V is survivable short-term. For reliable long-term use in NA556D-based designs, maintain V_CC ≤16 V with proper decoupling.

Does NA556D support true pin-to-pin replacement with NE556 or SA556?

Yes - NA556D shares identical pinout, electrical specifications, and functional behavior with NE556 and SA556 in SOIC-14 (D) and PDIP-14 (N) packages respectively. However, NA556D is rated for –40°C to +105°C, whereas NE556 is limited to 0°C to +70°C and SA556 to –40°C to +85°C. So NA556D is a direct drop-in for temperature-critical NA556D applications, but not vice versa.

Can NA556D drive a 12 V relay coil directly?

Yes - the NA556D output can sink or source up to ±200 mA, sufficient for most 12 V relay coils drawing <150 mA. When used as a low-side switch (output sinking current), connect relay coil between V_CC and OUT; when sourcing, connect between OUT and load ground. Always include a flyback diode across the coil. Confirm coil current at actual V_CC and temperature using NA556D's VOL/VOL specs.

What is the minimum monostable pulse width achievable with NA556D?

The minimum monostable pulse width for NA556D is 10 µs, as specified in TI SLFS023I Section 6.3.1. This limit arises from internal comparator storage time and cannot be reduced by adjusting R or C values. Attempting shorter intervals results in unreliable triggering or missed pulses. For sub-µs timing, consider dedicated high-speed timers like the TLC556 or digital solutions.

How does the CONT pin affect timing accuracy in NA556D?

The CONT pin in NA556D directly scales both trigger and threshold voltages proportionally - e.g., applying 2.5 V to CONT sets trigger ≈0.83 V and threshold ≈1.67 V when V_CC = 5 V. This enables precise analog modulation of timing intervals, but introduces nonlinearity due to RC exponential charging. For best accuracy, bypass CONT with a 10 nF ceramic capacitor to ground and avoid high-impedance modulation sources that load the internal divider.