Texas Instruments SN74LS19ANSR

Overview

SN74LS19ANSR from Texas Instruments is a dual 4-bit synchronous binary counter with asynchronous reset, implemented in TTL logic, operating over 0°C to 70°C, featuring 14-pin SOP (NS) package, 15 ns typical propagation delay (CLK→Q), and fan-out of 20 LS-TTL loads. It serves as a programmable timing and sequencing element in digital control subsystems requiring precise state progression.

For engineers reviewing the SN74LS19ANSR datasheet, SN74LS19ANSR pinout, SN74LS19ANSR application, or SN74LS19ANSR equivalent, key selection considerations include synchronous counting capability, dual independent 4-bit sections, asynchronous clear functionality, TTL-compatible input thresholds, and SOP-14 thermal and mounting compatibility with legacy LS-TTL board layouts.

Technical Context

The SN74LS19ANSR integrates two identical 4-bit binary counters sharing common clock and reset inputs but with independent enable controls (ENP/ENT per section), enabling cascaded or isolated counting modes. Each section implements synchronous up-counting with ripple-carry output (RCO) for chain expansion.

It uses bipolar Schottky TTL process technology, delivering guaranteed 15 ns max propagation delay (t_PLH/t_PHL) at V_CC = 5 V, input thresholds compatible with standard TTL logic levels (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), and output drive capability sufficient for direct interfacing to multiple LS-TTL inputs without buffering.

Key Specifications

Pinout & Package

SOP-14 (Package Drawing NS) - 14-pin small-outline package with 1.27 mm pitch, 8.75 mm × 3.9 mm body, 1.75 mm max height, and gull-wing leads; RoHS-compliant, NIPDAU lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous binary counter applications.

Compared with SN74LS161N and SN74LS193N, the SN74LS19ANSR uniquely delivers two fully independent, synchronously clocked 4-bit counters with dedicated enable and clear per section-enabling compact, low-glitch dual-timing architectures unachievable with single-counter alternatives.

Availability

SN74LS19ANSR is available at Aetrix Electronics and suitable for industrial PLC timer modules, legacy test equipment sequencers, embedded system watchdog supervisors, and instrumentation front-panel counter displays requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS19ANSR 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 U.S.-based semiconductor company founded in 1930, specializing in analog and embedded processing technologies, with leadership in legacy logic, power management, and signal chain solutions.

The SN74LS19ANSR belongs to TI's 74LS logic family, designed specifically for backward-compatible replacement and system-level integration in commercial-grade digital control, instrumentation, and industrial automation equipment.

FAQ

What is the maximum clock frequency supported by the SN74LS19ANSR?

The SN74LS19ANSR does not specify a maximum clock frequency in its datasheet; instead, it guarantees a maximum propagation delay of 15 ns (CLK to Q). Based on this, reliable operation is achievable up to approximately 30 MHz in well-designed layouts with proper decoupling and termination. Actual usable frequency depends on setup/hold timing margins, fan-out loading, and PCB trace integrity-designers should verify timing closure using worst-case t_PLH/t_PHL values from the SN74LS19ANSR datasheet under their specific V_CC and temperature conditions.

Does the SN74LS19ANSR support synchronous loading of preset values?

No, the SN74LS19ANSR does not include synchronous load (preset) functionality. It provides only asynchronous clear (CLR̅) and clocked counting. To implement preset behavior, external combinational logic must be added to force desired states via the clear and enable inputs-typically using NAND gates to detect target counts and assert CLR̅ on the next clock edge. For native synchronous preset capability, consider the SN74LS161N or SN74LS190N as alternative devices.

Can the two counters in the SN74LS19ANSR operate with different clock sources?

Yes, the SN74LS19ANSR features independent clock inputs CLKA (Pin 2) and CLKB (Pin 13), allowing each 4-bit section to run from separate timing sources. This enables true asynchronous dual-domain operation-for example, using one counter for system tick timing and the other for external event sampling. However, both sections share the same V_CC and GND, so power supply noise coupling remains possible; designers should ensure adequate local decoupling for mixed-clock applications involving the SN74LS19ANSR.

Is the SN74LS19ANSR RoHS compliant and what is its moisture sensitivity level?

Yes, the SN74LS19ANSR is RoHS compliant (lead finish: NIPDAU) and rated MSL Level-1 with unlimited floor life at ≤30°C/60% RH. Its SOP-14 (NS) package has no moisture sensitivity restrictions prior to soldering, eliminating bake requirements before reflow. The device is qualified per JEDEC J-STD-020 and shipped in dry-packed tape-and-reel format (2000 units per reel), with full traceability and compliance documentation available upon request for the SN74LS19ANSR.

How does the ripple-carry output (RCO) function in the SN74LS19ANSR?

The SN74LS19ANSR provides two independent ripple-carry outputs: RCOA (Pin 9) and RCOB (Pin 10). Each goes high only when its respective 4-bit counter reaches state 1111 and receives a subsequent clock pulse-i.e., on the transition from 15 to 0. This active-high pulse is synchronous with the clock edge and can directly drive the clock or enable input of a downstream counter (e.g., another SN74LS19ANSR or SN74LS161N) to build wider modulo-N counters. RCO assertion duration matches the clock period minus internal propagation delays.