SN74LS74AN Dual D Flip-Flop IC

The SN74LS74AN is a dual D flip-flop manufactured by Texas Instruments containing two independent positive-edge triggered D flip-flops with set and reset inputs. The SN74 family is characterized for operation from 0 °C to 70 °C.

 

SN74LS74AN Pinout Configuration

Pin Number	Pin Name	Description
14	VCC	Supply voltage, 5V nominal
1, 13		Clear input, equivalent to reset
2, 12	D	Data input
3, 11	CLK	Clock input, rising edge triggered
4, 10		Preset input, equivalent to set
5, 9	Q	Output
6, 8		Inverted output
7	GND	IC ground reference

 

Features and Specifications

• Dual D flip-flops in the same package
• Positive edge-triggered
• Preset and Clear inputs

 

Note: Complete technical details can be found in the SN74LS74AN datasheet linked at the end of this page.

 

SN74LS74AN Equivalents

74HC74, 74HCT74

 

Other D Flip-Flops

CD4013

 

How To Use SN74LS74AN?

The SN74LS74AN is a dual D-type positive edge-triggered flip-flop with set and clear inputs.

A flip-flop is a basic ‘memory’ circuit – the output remembers the previous input state unless the power to the IC is turned off. Data is fed into the D pin (D for data), and when the chip registers a rising edge on the CLK (clock) pin, the data is transferred to the Q and  pins. After this, any input on the D pin does not get transferred to the output pins unless there is once again a rising edge on the CLK pin.

The CLK pin is usually fed with a periodic clock signal, and this can be used to synchronize external inputs to a clocked synchronous circuit.

The SN74LS74AN also comes with and  pins, which is the equivalent of set and reset pins on a regular flip-flop. On this chip, these two inputs override the D and CLK pins – regardless of their state, setting  low turns Q high and  low, and setting  low turns Q low and  high. If these pins are not used, they can be tied to V_CC.

The ‘LS’ in the part number means low-power Schottky, meaning that the transistors that make up the IC are NPN transistors with a base-collector Schottky diode that prevents saturation and speeds up the transistor. This also means that the input logic thresholds are 0.8V for low and 2V for high respectively, which might not be compatible with other logic ICs, care should be taken while interfacing ICs between logic families.

 

Applications

• Data storage
• Data synchronization
• Quadrature generator

 

2D Model and Dimensions

If you are designing a PCB or Perf board with this component then the following picture from the Datasheet will be useful to know its package type and dimensions.