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74LS Datasheet(PDF) – TI store

74lss540 Typ Max Unit. This is a modified output circuit within the chip which sinks current to indicate a logic “0,” but turns off to indicate a logic “1. Since open collector is often used where “0” is the active state, this is datasjeet called a “wired-OR” connection, referring to an active-low OR function.

However part of the current reduction in the 74LS00 family was on inputs, such that a typical 74LS00 family part can drive twenty LS loads that is, one output can fan out to twenty inputs within the 74LS00 family; compare this to the family, which could only drive ten inputs in the same family. Motorola does not convey 74sl540 license under its patent rights nor the rights of others. Motorola 74lx540 are registered trademarks of Motorola, Inc.

Motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. These four-bit counter parts can count up or down. These device types are designed to be used as memory address drivers.

Tri-state outputs allow multiple gates to “take turns” driving an datasheeet signal. There datashdet some other family offshoots; this list is those flavors of currently in production from one manufacturerTexas Instruments. These chips have convenient pin-outs separating the input side from the output side. Motorola makes no warranty, representation or guarantee regarding.

For a long time, the original series was the best choice as a general-purpose logic family, and the family had more members than any of the offshoot families. The 74LS00 family We’ve already spent time looking at the TTL logic family, even though I only introduced the first part in the family.

74LS540 数据手册 ( 数据表 ) – Motorola => Freescale

Parts which are capable of having their output in any of these three states are considered to have “tri-state” outputs. These devices are especially useful as output ports for the microprocessors, allowing ease of layout and greater PC board density. These can be used in cases where the final output of a logic function only needs to sink current; a later section will give examples where this can be used.


The 74LS is an eight-bit transparent latch, while the 74LS is an eight-bit edge-triggered latch. Because tri-state buffers have many applications in microprocessor circuits, there 74ls5400 several useful chips available which are designed to function on eight data signals bits at one time.

The datasjeet family improves technically on the family in two key areas: Motorola products are not designed, intended, or authorized for use as components in. Since a regular TTL logic gate sources current for “1” and sinks current for “0,” a signal where neither of these is happening the signal is “off,” like in open collector outputs can actually be thought of as being a third state.

If all outputs are off, the combination of signals is also off. The series was very successful and very popular, to the extent that when companies want to manufacture new logic parts with different electrical datsaheet, they typically create new families of the very same functions and pin-outs.

Open collector gates have an interesting property, which is that they can be ANDed together just by wiring several outputs together.

There are six of these on a single chip. Motorola reserves the right to make changes without further notice to any products herein. Ordinarily this is a Bad Thing because outputs could drive into each other, but for open collector it’s fine: Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a datassheet where personal injury or death may occur.

The only limitation of the 74LS00 family compared to the family is that the 74LS00 family can only source half as much current. Should Buyer purchase or use Motorola products for any such. This family arguably has the widest manufacturer support and range of available line of components.

74LS (TI) – Octal Buffers and Line Drivers With 3-state Outputs | eet

Although less common, there are decimal versions of these chips. Latches The 74LS is an eight-bit transparent latch, while the 74LS is an eight-bit edge-triggered latch. The eight-bit buffers 74LS and 74LS are functionally equivalent to the widely used 74LS and 74LS; however the ‘ and ‘ have a more confusing pin-out to trip the unwary student. Box ; Phoenix, Arizona When the enable is “1” the buffer is driving the output; when the enable is “0,” the output is turned off “tri-stated”.


This section introduces a number of useful digital logic chips for use in a variety of projects. Outputs Q0 through Q3 are a binary value, where Q0 is the least signifigant bit and Q3 is most significant. Many of the basic logic functions are also available in parts with “open collector” outputs. Schematics and Components Previous: A tri-state buffer or inverting buffer looks like a regular buffer or inverter, except there is an additional “enable” control signal entering the gate.

Along the way I’ll also cover some additional chip characteristics that can be useful in complex designs. You might use these variants if you want to count in decimal digits rather than pure binary.

As long as other logic determines that no more than one output is driving the same signal at the same time, all is well. Two-input logic gates The five standard two-input logic gates in the 74LS00 family are listed in the table below. The truth tables for the 74LS and 74LS introduce a new symbol, “Z,” which represents the “off” state.

You might signal a logic function to drive its output high or low as the function may determineand then later tell that function to turn off its output so that a different function may drive the signal instead. This method of combining multiple outputs on the same signal path is used heavily in microprocessor circuits, where several different memory or input circuits may be sharing a common set of data signals.

There are plenty of other useful chips in the 74LS00 logic family, but these are some of the most useful building blocks. 74,s540 has an output enable pin that can tri-state all the outputs.