Gate circuit is the basis of constructing a combinational logic circuit while latch and flip-flop are the basis for constructing a sequential logic circuit. Though these two components are commonly used in all aspects of the electronic industry, confusions upon latches and flip flops (or FFs) are frequently come up from beginners. Therefore, Easybom took a comprehensive look at the question and here’s what we found.
What is a Latch?
A latch is a kind of digital memory circuit formed of gates but not combinatorial. Their outputs value is generated depending shortly after the inputs are applied in the diagram of the device. By doing so, latches are usually used as a data memory device in some arithmetic circuits through a feedback lane. Generally, they can be classified into several types including JK latch, Gated D latch, Gated SR latch, D latch, SR latch and T latch.
What is a Flip Flop?
To put it simpler, a flip flop (or a bistable multivibrator) is the synchronous variant of a latch, which means that it works accordingly as the clock pulse turns active/inactive. Similarly, flip flops can be categorized into kinds like D-type, SR-type, T-type, JK-type. Moreover, except for the register function in loading data (at which a latch isn’t quite good), flip flops can be used for applications such as RAM (Random Access Memory) used in computers and other information process systems.
Differences between the Two
In brief, a flip-flop is made up of latches by implementing an extra clock signal and the latter is constituted by gate circuits. A latch can hold the result by itself according to the input; a flip flop is the memory cell triggered by the edge of the clock. A latch controlled by the sensitive signal (level, edge) is the flip-flop.
However, they are distinct from each other in many other ways that influence a lot in industrial practice as follows.
- Contrasted with the latches that cannot be classified, a flip flop can be classified into asynchronous or synchronous kinds.
- To a flip flop, there’s always a clock signal in it while there’s none of that for a latch to obtain.
- A flip flop is a clock-edge-trigged component. By contrast, a latch is a level-triggered component.
- A latch verifies the inputs changes constantly to which it reacts almost at the same time. But a flip flop would always check the inputs and modify the outputs only when the clock pulse turns active.
- Relatively, Latches are faster than flip flops. Latches are common in CPU designs, and it is precisely because it has made the CPU much faster than external IO component logic.
- Additionally, a latch is typically smaller in proportion than that of a flip flop due to its different structures.
- In terms of power consumption, latches are energy-saving components. Flip flops consume more power.
- Latches are more independent for the reason that it doesn’t require a clock signal to finish its job whereas flip flops need both the clock signals and binary inputs.
- Latches are inclined to be interrupted by noise because of asynchronous design.
- When it comes to Static Timing Analysis (STA), flip flops are preferred over latches.
Conclusion
Since both two components have advantages and disadvantages, Easybom would like to draw every engineer’s attention that we should choose the appropriate solution to meet our projects’ needs.