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Advantages of latch over flip flop

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Member level 1
Nov 21, 2005
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Can anybody tell me some advantages of latch over flip flop except area advantage??

Also if sumbody can give some digital interview questions??


In a flip flop based design, when considering the clock period, we need to consider three aspects

1. Clock to Q delay.
2. Time taken by logic
3. Setup time

In a FF-based design Clock-to-Q delay and setup time are overheads and need to be addressed at all stages of the design. Therefore, if you try to reduce the clock period simply by reducing the time taken by logic, you will see at one point of time the overheads mentioned above become significant contributing factor to the higher clock rates.
In a latch-based design however, that overhead is paid for only once. Therefore, we can achieve higher clock speeds. Also there is a phenomenon called "time-borrowing". In this case, if one stage cannot finish its operation on time, then a certain amount of time can be borrowed from the subsequent stages, something that cannot be acheived in a FF based design.

Hope this answer helps.
Another good qus for interview is.......

Why JK flipflop is prefered over D flipdlop?

Latch-based design has small die size, while to flip-flop based design clock skew is a big problem when the clock frequency is in G-hz level.

Time sharing and time borrowing is the significant adv for latch in case of robust design.....But still latches are not prefferd over FF....

Using JK FF we can implement many function with lesser number of combinational gates...thus lesser delay....whereas with D FF size of Comb block will increase at each stage....
Latch-based design has small die size,time-borrowing is less etc.

As u know latches are level triggered and ffs are edged triggered, thus latches can easily be used in Asynchronous design. An Asynchronous design where clock is not used, it uses handshaking between various logic blocks. Thus it is more faster than synchronous design.

well, here some basic digital questions in attached document.
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