Texas Instruments SN74LS174NSR

Overview

SN74LS174NSR from Texas Instruments is a hex D-type flip-flop with asynchronous clear, implemented in low-power Schottky TTL logic. It contains six independent edge-triggered D flip-flops sharing a common clock and master clear, operates at 0–70°C, supports 5 V ±5% supply, and delivers typical propagation delay of 15 ns (t_PLH/t_PHL) at V_CC = 5 V. It is used in synchronous data latching, register file construction, and clock-domain synchronization in legacy industrial control logic.

For engineers reviewing the SN74LS174NSR datasheet, SN74LS174NSR pinout, SN74LS174NSR application, or SN74LS174NSR equivalent, this page provides verified functional identity, SOP-16 package mapping, timing parameters, real-world use cases, and validated alternative parts for register-level design continuity.

Technical Context

The SN74LS174NSR implements six positive-edge-triggered D flip-flops with a shared asynchronous active-low clear (/CLR) input and a common clock (CLK). All flip-flops update on the rising edge of CLK only when /CLR is high; asserting /CLR forces all Q outputs low regardless of clock or D inputs.

It belongs to the 74LS family and uses bipolar transistor–transistor logic with Schottky clamping for improved speed–power trade-off versus standard 74TTL. Input thresholds are compatible with TTL voltage levels (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), and output drive capability is rated for 8 LSTTL loads (I_OH/I_OL = –0.4 mA / 8 mA).

Key Specifications

Pinout & Package

SOP-16 (NS) package: 16-pin small-outline plastic package with gull-wing leads, 1.27 mm pitch, body width 5.3 mm, and JEDEC MS-012AC compliant footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar hex D-type flip-flop applications.

Compared with SN74LS174N, SN74LS174NSR offers surface-mount reliability and higher board density; compared with SN74LS175DR, it provides six fully independent channels with unified reset-making it optimal for 6-bit register consolidation where pin-for-pin replacement is not required but functional equivalence is critical.

Availability

SN74LS174NSR is available at Aetrix Electronics and suitable for industrial control registers, legacy test equipment data capture, and microcontroller peripheral interface applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74LS174NSR 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, embedded processing, and logic solutions with broad industrial and automotive qualification.

The SN74LS174NSR belongs to TI's legacy 74LS logic product line, designed for backward compatibility with TTL-based digital systems requiring reliable, low-speed synchronous storage in commercial-temperature environments.

FAQ

What is the maximum clock frequency supported by the SN74LS174NSR?

The SN74LS174NSR does not specify a maximum clock frequency in its datasheet; instead, it guarantees a maximum propagation delay of 15 ns (CLK to Q) and minimum pulse width requirements (CLK high/low ≥ 20 ns). Designers derive practical maximum frequency from timing margins: for robust operation with standard setup/hold times, 25 MHz is a conservative upper limit in typical conditions. The SN74LS174NSR is intended for medium-speed logic-not high-frequency applications-and should be validated with actual board-level timing analysis.

Can the SN74LS174NSR be used with a 3.3 V supply?

No, the SN74LS174NSR is not rated for 3.3 V operation. Its absolute maximum supply voltage is 5.5 V, and its recommended operating range is 4.75 V to 5.25 V. At 3.3 V, input thresholds (V_IH ≥ 2.0 V, V_IL ≤ 0.8 V) may not be met reliably, and output drive strength collapses below specification. Using SN74LS174NSR at 3.3 V risks logic failures, increased static current, or permanent damage. For 3.3 V systems, consider modern 74LVC or 74ALVC series alternatives.

Does the SN74LS174NSR have individual data inputs for each flip-flop?

Yes, the SN74LS174NSR provides six independent data inputs: D1 through D6, each feeding one of the six D-type flip-flops. These inputs operate in parallel and are sampled simultaneously on the rising edge of the shared CLK signal. There is no internal gating or multiplexing between D inputs - each controls its corresponding Q output exclusively, enabling true 6-bit parallel data storage in the SN74LS174NSR.

Is the /CLR input of the SN74LS174NSR synchronous or asynchronous?

The /CLR input of the SN74LS174NSR is asynchronous: asserting /CLR low forces all six Q outputs immediately to logic low, regardless of the state or timing of the CLK signal. This behavior is confirmed in the SDLS068A datasheet truth table and functional description. The SN74LS174NSR does not require a clock edge to activate clear - making it suitable for emergency reset, power-on initialization, and fault-handling circuits where deterministic, immediate state clearing is required.

What is the meaning of "NS" in the SN74LS174NSR part number?

The "NS" in SN74LS174NSR denotes the package type: SOP (Small Outline Package) with 16 pins and a 1.27 mm lead pitch, per TI's standard package designation. The "R" suffix indicates tape-and-reel packaging (2000 units per reel), and the absence of "E4" or "A" means it is the base commercial-grade variant. This distinguishes SN74LS174NSR from PDIP (N), SOIC (D), or military-grade (J/W/FK) versions - all sharing identical logic functionality but differing in mechanical form and qualification.