Texas Instruments SN74HC74PWG4

Overview

SN74HC74PWG4 from Texas Instruments is a dual D-type positive-edge-triggered flip-flop with asynchronous clear and preset inputs per channel, operating across 2 V to 6 V supply voltage and -40°C to +85°C temperature range. It delivers 39 ns max propagation delay (VCC = 6 V), supports fanout of up to 10 LSTTL loads, and enables clock division by 2 or 4 in digital timing circuits.

For engineers reviewing the SN74HC74PWG4 datasheet, SN74HC74PWG4 pinout, SN74HC74PWG4 application, or SN74HC74PWG4 equivalent, this device serves as a foundational building block for synchronous logic design, toggle switch conversion, and low-power edge-triggered state storage in industrial control, instrumentation, and embedded interface subsystems.

Technical Context

The SN74HC74PWG4 implements two independent CMOS D-type flip-flops sharing no internal coupling-each with dedicated asynchronous active-low PRE and CLR inputs, data (D), clock (CLK), true (Q), and complement (Q) terminals. Its positive-edge-triggered behavior ensures state updates only on rising CLK transitions, while buffered inputs reduce noise susceptibility and improve drive capability.

It operates under standard HCMOS logic levels with input thresholds scaling proportionally with VCC (e.g., VIH = 3.15 V at VCC = 4.5 V), and features balanced push-pull outputs capable of sourcing/sinking ±4 mA (VCC = 4.5 V) while maintaining VOL ≤ 0.26 V and VOH ≥ 3.98 V under load-enabling reliable interfacing with TTL and other CMOS families.

Key Specifications

Pinout & Package

TSSOP-14 package (5.00 mm × 4.40 mm body size, 0.65 mm lead pitch), surface-mount, moisture-sensitive level 1 (MSL-1), RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC74PWG4, SN74HCT74PW offers superior noise immunity in TTL-dominated environments but consumes twice the quiescent current, while MC74HC74ADTR2G provides automotive qualification and identical electrical behavior at the cost of minor PCB layout adjustment.

Availability

SN74HC74PWG4 is available at Aetrix Electronics and suitable for industrial control logic, digital instrumentation, embedded interface subsystems, and test & measurement equipment requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for SN74HC74PWG4 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 logic solutions, with over 50 years of innovation in high-reliability digital ICs.

The SN74HC74PWG4 belongs to TI's industry-standard 74HC logic family, designed specifically for low-power, wide-supply-voltage digital control and signal conditioning in industrial, automotive, and communications infrastructure applications.

FAQ

What is the maximum clock frequency supported by SN74HC74PWG4 at 3.3 V supply?

The SN74HC74PWG4 supports a maximum clock frequency of 25 MHz at VCC = 4.5 V and TA = –40°C to +85°C. At 3.3 V, the datasheet does not specify a guaranteed maximum; however, based on interpolation of timing characteristics (fclock = 31 MHz at 4.5 V, 6 MHz at 2 V), operation up to ~18 MHz is feasible with derated margins. For production use at 3.3 V, verify timing margins using actual board-level measurements and worst-case voltage/temperature conditions. The SN74HC74PWG4 remains fully functional across the entire 2–6 V range, but AC performance scales with supply voltage.

Can SN74HC74PWG4 be used as a toggle flip-flop, and how is it configured?

Yes, the SN74HC74PWG4 can be configured as a toggle flip-flop by connecting the Q output to the D input of the same channel. On each rising edge of CLK, the output toggles between HIGH and LOW states. This configuration is explicitly cited in the official TI datasheet (Section 2 Applications) for converting momentary switches into toggle functions. To ensure reliable operation, the CLK input must be debounced (e.g., via RC filter + Schmitt trigger), and PRE/CLR pins must be held HIGH. The SN74HC74PWG4's asynchronous controls allow forced initialization to a known state at power-up.

Does SN74HC74PWG4 require external pull-up resistors on unused inputs?

Yes, all unused inputs of the SN74HC74PWG4-including PRE, CLR, D, and CLK-must be terminated to either VCC or GND to prevent floating states that cause excessive current draw, oscillation, or undefined outputs. TI recommends 10-kΩ pull-up or pull-down resistors for unused inputs, as specified in Section 9.2.1.2 of the datasheet. Leaving inputs unconnected violates HCMOS design rules and may result in erratic behavior or increased power consumption. The SN74HC74PWG4 has no internal pull-ups or pull-downs; external biasing is mandatory for robust operation.

What is the thermal resistance (RθJA) of SN74HC74PWG4 in its TSSOP-14 package?

The junction-to-ambient thermal resistance (RθJA) for SN74HC74PWG4 in the TSSOP-14 (PW) package is 151.7 °C/W, as specified in Section 6.4 of the TI datasheet (SCLS094F). This value assumes standard JEDEC 2-layer board conditions (1-inch² copper pad). Actual thermal performance improves significantly with PCB copper area, thermal vias, and airflow. For continuous operation near maximum ratings, ensure ambient temperature plus (ICC × VCC + IOUT² × RDS_ON) × RθJA stays below 125°C junction limit. The SN74HC74PWG4's low ICC (4 µA typical) makes self-heating negligible in most applications.

Is SN74HC74PWG4 pin-compatible with SN74HC74N (PDIP-14)?

Yes, the SN74HC74PWG4 is functionally and pinout-compatible with SN74HC74N and all other variants in the SN74HC74 family (e.g., D, DB, NS, PW), as confirmed by TI's "Device Information" table and identical pin function mapping across packages. All share the same 14-pin assignment: pins 1–7 and 8–14 correspond to 1CLR, 1D, 1CLK, 1PRE, 1Q, 1Q, GND and 2Q, 2Q, 2PRE, 2D, 2CLK, 2CLR, VCC respectively. However, physical dimensions, solder reflow profiles, and moisture sensitivity differ-so PCB layout and assembly processes must match the specific package (TSSOP-14 for SN74HC74PWG4).