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SN74LS74AN

Dual D flip-flop, edge-triggered, preset/clear, LS TTL, PDIP-14

11000

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Pieza del fabricante：

SN74LS74AN

Paquete：

PDIP-14 (19.3 x 6.35 x 4.57mm, 2.54mm pitch, through-hole)

Marca：

Categorías de productos：

Circuitos integrados IC, Circuitos integrados de interfaz

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Descripción

Productos

The SN74LS74AN is a dual positive-edge-triggered D-type flip-flop from Texas Instruments with preset, clear, and complementary outputs in a 14-pin PDIP package.

Especificaciones

Number of Flip-Flops	2 (dual)
Trigger Type	Positive-edge-triggered
Logic Family	LS (Low-power Schottky)
Tensión de alimentación	4.75V to 5.25V (5V nominal)
Max Clock Frequency	25MHz typical
Propagation Delay (CLK to Q)	25ns typical
Preset (Active Low)	Yes (asynchronous, sets Q=HIGH)
Clear (Active Low)	Yes (asynchronous, sets Q=LOW)
Outputs	Q and Q-bar (complementary)
Output Current (IOL)	8mA
Temperatura de funcionamiento	0°C to +70°C
Paquete	PDIP-14 (19.3 x 6.35mm)

Características

Dual independent D flip-flops in one package
Positive-edge-triggered clock
Asynchronous preset (active low) and clear (active low)
Complementary Q and Q-bar outputs
Direct replacement for 7474 and 74LS74
Input clamp diodes for undershoot protection

Aplicaciones

Frequency division and counters
Data synchronization and storage
Shift register construction
One-shot and toggle circuits
Control state machines

Introducción del producto:SN74LS74AN Presentación del producto

The SN74LS74AN from Texas Instruments contains two independent positive-edge-triggered D-type flip-flops with asynchronous preset and clear inputs in a 14-pin PDIP through-hole package. Each flip-flop transfers the logic level at the D input to the Q output on the rising edge of the clock (CLK). The asynchronous preset (PRE, active low) forces Q HIGH regardless of the clock or D input. The asynchronous clear (CLR, active low) forces Q LOW regardless of the clock or D input. Both PRE and CLR override the clock, and applying both simultaneously is prohibited (Q and Q-bar would both be HIGH). The complementary outputs (Q and Q-bar) provide both true and inverted data. The device is a direct replacement for the classic 7474 and 74LS74 from any manufacturer. The AN suffix denotes the improved LS version in the PDIP-14 package.

Principio de funcionamiento:SN74LS74AN Principio de funcionamiento

Each D flip-flop in the SN74LS74AN captures the logic state present at its D input on the rising edge of the CLK signal. When CLK transitions from LOW to HIGH, the D input value is latched and appears at the Q output after the propagation delay (25ns typical). The Q-bar output provides the complement. If D is HIGH at the clock edge, Q goes HIGH; if D is LOW, Q goes LOW. The D input must be stable for a setup time (typically 15ns) before the clock edge and held for a hold time (typically 0ns) after the edge. The asynchronous PRE input, when pulled LOW, immediately forces Q HIGH (and Q-bar LOW) regardless of the CLK and D states. Similarly, the CLR input, when pulled LOW, forces Q LOW (and Q-bar HIGH). These asynchronous inputs are level-sensitive and override the synchronous (clocked) operation. When both PRE and CLR are HIGH (inactive), the flip-flop operates in the normal clocked mode. The flip-flop can be wired as a toggle (divide-by-2) by connecting Q-bar to D; each clock edge then toggles the output, dividing the clock frequency by two.

Descripción de la clavija:SN74LS74AN Definición y funciones de las clavijas

Pin	Nombre	Tipo	Descripción
1	1CLR	Entrada	Flip-flop 1 clear (active low, async)
2	1D	Entrada	Flip-flop 1 data input
3	1CLK	Entrada	Flip-flop 1 clock (rising edge triggered)
4	1PRE	Entrada	Flip-flop 1 preset (active low, async)
5	1Q	Salida	Flip-flop 1 true output
6	1Q-bar	Salida	Flip-flop 1 complement output
7	GND	Potencia	Suelo
8	2Q-bar	Salida	Flip-flop 2 complement output
9	2Q	Salida	Flip-flop 2 true output
10	2PRE	Entrada	Flip-flop 2 preset (active low, async)
11	2CLK	Entrada	Flip-flop 2 clock (rising edge triggered)
12	2D	Entrada	Flip-flop 2 data input
13	2CLR	Entrada	Flip-flop 2 clear (active low, async)
14	VCC	Potencia	Supply (4.75V to 5.25V)

Application Scenarios:In which products and applications isSN74LS74AN usado

Frequency Divider: Connect Q-bar to D for divide-by-2; cascade for binary counters (÷4, ÷8, etc.)
Data Sync: Capture asynchronous input on clock edge to synchronize to system clock domain
Shift Register: Chain D-to-Q connections for serial-to-parallel conversion or delay lines
State Machine: Q and Q-bar outputs provide current and complement states for Moore/Mealy FSM
One-Shot: D tied HIGH with CLK as trigger creates a pulse-width set by external clear timing

Alternative Models:What chips are recommended as replacements for SN74LS74AN

Modelo	Fabricante	Diferencia clave	Paquete	Supply
74LS74N	TI/Nexperia	Original TTL version with 5V-only supply, typical propagation delay 10-15ns	DIP-14	5V TTL
74LS74D	TI/Nexperia	Surface-mount SOIC version of LS with identical logic function	SOIC-14	5V TTL
74HC74D	TI/Nexperia	CMOS version with wide 2-6V supply range, lower power consumption and higher noise immunity	SOIC-14	2-6V CMOS
74HC74N	TI/Nexperia	Through-hole DIP version of HC family for prototyping and repair	DIP-14	2-6V CMOS
74HCT74D	TI/Nexperia	CMOS with TTL-compatible input levels, ideal for mixing with LS devices at 5V	SOIC-14	4.5-5.5V TTL-in
74HCT74N	TI/Nexperia	Through-hole DIP version of HCT family for prototyping and repair	DIP-14	4.5-5.5V TTL-in
74AC74D	TI/Nexperia	Advanced CMOS with 2-6V supply and higher output drive current (24mA vs 6mA for HC)	SOIC-14	2-6V CMOS
74AC74N	TI/Nexperia	Through-hole DIP version of AC family for prototyping and repair	DIP-14	2-6V CMOS
74LVC74D	TI/Nexperia	Low-voltage CMOS for 1.65-3.6V modern logic with 24mA output drive and bus-hold inputs	SOIC-14	1.65-3.6V CMOS
74LVC74N	TI/Nexperia	Through-hole DIP version of LVC family for prototyping and repair	DIP-14	1.65-3.6V CMOS

The 7474 is a Dual D-Type Positive-Edge-Triggered Flip-Flop. Family variants span from the original LS TTL (5V only) to modern LVC/AUP (down to 0.8V). HC and HCT versions offer 2-6V CMOS operation with HCT providing TTL-compatible input thresholds for mixed 5V systems. CD4000-series equivalents offer the widest 3-18V supply range at the cost of lower switching speed. DIP packages (N suffix) are through-hole; SOIC (D suffix) and TSSOP are surface-mount.