74LS279 Quad Set-Reset Latches


The 74LS series of integrated circuits (ICs) was one of the most popular logic families of transistor-transistor logic (TTL) logic chips. 74LS series is a bipolar, low-power Schottky IC. The 74LS279 offers 4 basic S-R flip-flop latches in one 16-pin, 300-mil package. Under conventional operation, the S-R inputs are normally held high. When the S input is pulsed low, the output will be set high. When R I pulsed low, the Q output will be reset low.

74LS279 Features

  • Four Individual and Independent Set-Reset Latches
  • Inputs Voltage Level Triggered
  • Fast Propagation Times
  • Operating Temperature up to 70°C
  • Standard TTL Switching Voltages

74LS279 Specifications

Supply Voltage4.75 – 5.25Vdc
Maximum Clock Frequency40Mhz
Power Dissipation2mW/gate @100kHz
Minimum Output Current8mA
Propagation Delay10nS
Fan Out (TTL Loads)20

74LS279 Pinout Diagram

74LS279 Pin Description

Pin NoPin NameDescription
1RReset Pin
2S1Set Pin 1 Of Latch 1
3S2Set Pin 2 Of Latch 1
4QOutput Of Latch 1
5RReset Pin
6S1Set Pin 1 Of Latch 2
7QOutput Of Latch 2
8GNDGround Pin
9QOutput Of Latch 3
10R’Reset Pin(Active Low)
11S’2Set Pin(Active Low) of Latch 3
12S’1Set Pin(Active Low) of Latch 3
13QOutput Of Latch 4
14R’Reset Pin(Active Low)
15S’1Set Pin(Active Low) of Latch 4
14VCCPositive Supply


  • As the latch is a single-bit storage element, it may be used as a storage device in power gating circuits and clock.
  • They may be used as pulse latches where they perform the same behavior as flip-flops by pulsing the clock very quickly.

74LS279 Alternative Equivalent

Download the 74LS279 Quad Set-Reset Latches Datasheet from the link given below.