What is TTL level and cmos level? What is the difference between ttl level and cmos level?
I believe that many people have a certain understanding of voltage, current, and electric power, but when it comes to level, many people can’t tell why, let alone TTL level. TTL is the abbreviation of Time To Live, which means the time-to-live value, and its function is to limit the existence time of IP data packets in the computer network. So what does the ttl level mean? Let’s talk about what is TTL level? And the difference between ttl level and cmos level.
1. What is TTL level?
The level refers to the relative ratio of two or several points in the circuit under the same impedance. The power here naturally refers to “voltage”, “current”, and “electric power” and the multiples are converted into logarithms, expressed in “decibels” and recorded as “dB”. Respectively recorded as: 10lg (P2/P1), 20lg (U2/U1), 20lg (I2/I1) In the above formula, P, U, and I are electric power, voltage, and current respectively. Commonly used levels are power level and voltage level, which can be divided into absolute level and relative level.
The TTL level refers to the level suitable for ttl circuit work. The working voltage of TTL power supply is 5V, then 5V can be high level, and 0V can be low level. However, there are standard requirements for the high and low levels of data transmitted by ttl, the input high level is >=2.0V, and the input low level is
TTL level signals are most used because usually data representation is specified in binary, +5V is equivalent to logic “1”, and 0V is equivalent to logic “0”, which is called TTL (transistor-transistor logic level) signal System, which is a standard technique for communication between parts inside a device controlled by a computer processor.
2. What is cmos level?
In the same way, the level suitable for cmos circuit work is the cmos level. CMOS integrated circuit is the English abbreviation of complementary symmetric metal oxide semiconductor (Compiementary symmetry metal oxide semiconductor) integrated circuit. Many basic logic units of the circuit are connected in a complementary symmetrical form with enhanced PMOS transistors and enhanced NMOS transistors. Static power Consumption is very small. The power supply voltage VDD of the COMS circuit is relatively wide and can work normally at +5–+15V, and the voltage fluctuation is allowed to be ±10. When the output voltage is higher than VDD-0.5V, it is logic 1, and the output voltage is lower than VSS+0.5V ( VSS (digital ground) is logic 0, and the fan-out number is 10–20 COMS gate circuits.
cmos logic gate circuit
3. The difference between ttl level and cmos level
A logic level of 1 is close to the supply voltage, and a logic level of 0 is close to 0V. And has a very wide noise margin.
3. Level conversion circuit:
Because the high and low levels of TTL and COMS have different values, level conversion is required when connecting to each other: that is, use two resistors to divide the level!
4. Comparison of TTL and COMS circuits:
(1) The TTL circuit is a current control device, while the coms circuit is a voltage control device.
(2) The speed of the TTL circuit is fast, and the transmission delay time is short (5-10ns), but the power consumption is large.
The speed of the CMOS circuit is slow, the transmission delay time is long (25-50ns), but the power consumption is low.
The power consumption of the COMS circuit itself is related to the pulse frequency of the input signal. The higher the frequency, the hotter the chip set, which is a normal phenomenon.
(3) Lock-in effect of COMS circuit:
Due to the large input current of the COMS circuit, the internal current increases sharply, and the current keeps increasing unless the power supply is cut off. This effect is the lock-in effect. When the lock-in effect occurs, the internal current of COMS can reach more than 40mA, and it is easy to burn the chip.
(1) Add clamping circuits at the input and output terminals so that the input and output do not exceed the specified voltage.
(2) A decoupling circuit is added to the power input terminal of the chip to prevent instantaneous high voltage at the VDD terminal.
(3) Add a line resistor between VDD and the external power supply, even if there is a large current, don’t let it go in.
(4) When the system is powered by several power supplies, the switch should be in the following order: when it is turned on, turn on the power supply of the COMS circuit first, and then turn on the power supply of the input and load; when it is turned off, first turn off the power supply of the input signal and the load, and then Close COMS
The power supply voltage of CMOS integrated circuits can vary in a wide range, so the requirements for power supply are not as strict as those of TTL integrated circuits. Therefore, they can be compatible with TTL levels if conditions permit. It should be noted that their driving capabilities are different, and the driving ability of CMOS will be larger. Sometimes the low level of TTL cannot trigger the CMOS circuit, and sometimes the high level of CMOS will damage the TTL circuit. Pay attention to compatibility.
Микросхемы CMOS и TTL: в чем разница
Аббревиатура CMOS (Complementary Metal-Oxide Semiconductor) или КМОП (комплементарный металл-оксид-полупроводник) означает, что структура интегрального компонента построена на полевых транзисторах.
TTL (Time To Live) расшифровывается как ТТЛ (транзисторно-транзисторная логика). Это способ построения микросхем на биполярных транзисторах. Отличаются они параметрами, свойствами и уровнями логических значений. Есть комплексные микросхемы, использующие в своём составе обе технологии.
Основные отличия CMOS от TTL
Технология CMOS была запатентована в 1967 году, когда с 1961 года вместе с диодной и резисторной логикой уже использовалась TTL. Логические вентили TTL были в приоритете использования, так как обладают высокой устойчивостью к электромагнитным помехам. А структура CMOS всегда отличалась высоким входным сопротивлением и малым энергопотреблением.
Однако с повышением частоты переключения каскадов CMOS, их ток потребления сильно возрастает. А из-за высокоомности входных цепей, помехоустойчивость резко падает. Этот недостаток был причиной редкого использования микросхем такого типа в скоростной цифровой электронике. Лишь постоянные усовершенствования и доработки топологии позволили не только улучшить свойства, но и добиться приоритета в применении.
- более критичны к напряжению питания;
- потребление мощности с ростом частоты остаётся практически на неизменном уровне.
Согласование цифровых уровней CMOS и TTL
Логические уровни CMOS и TTL имеют отличия, поэтому они не всегда совместимы для разных типов логики. У некоторых интегральных компонентов входы или выходы могут быть приспособлены для совместного использования. Существуют специальные логические элементы, которые преобразуют цифровой сигнал CMOS в TTL или наоборот.
Отличительные свойства техники CMOS от TTL при разных условиях эксплуатации
Многим потребителям кажется, что техника, построенная по CMOS-технологии лучше, чем на микросхемах TTL из-за низкого потребления тока каскадами логики. Это так, если не учитывать среду эксплуатирования и степень защиты IP корпуса. Логические элементы TTL имеют меньшее сопротивление входных и выходных цепей, которое снижает экономичность. А это значит, что влияние влажности среды на межплатные соединения элементов монтажа остаётся минимальным.
Монтажные соединения микросхем, построенных на полевых транзисторах, производители покрывают лаком. Этим простым способом якобы решается проблема защиты от влаги. Однако на практике это улучшение служит не долгое время. Если в лаке образуются трещины и в них попадает влага, то это может привести к сбоям в работе устройства, собранного по CMOS-технологии. TTL в этом плане менее критичны.
На практике, если электронику предполагается использовать в условиях с повышенной влажностью, поплатившись повышенным потреблением, то используют TTL микросхемы. Пример аппаратов:
- персональные компьютеры, серверы;
- электроника транспортной техники;
- автоматика и приборы, используемые в экстремальных условиях;
- датчики и пр.
Для переносной техники важным параметром является экономичность, поэтому для ее создания используют микросхемы технологии CMOS. Этой структурой обладают преимущественно такие устройства:
- ноутбуки и нетбуки;
- сотовые телефоны, смартфоны, планшеты;
- переносные устройства и гаджеты.
Качество электронных устройств напрямую зависит от используемых в ней компонентов. Компания «ЗУМ-СМД» имеет обширный каталог микросхем и микроконтроллеров, собранных по технологии CMOS и TTL и используемых для различных сфер производства электронной техники.
ECSTUFF4U for Electronics Engineer
CMOS stands for complementary metal-oxide-semiconductor is also another classification of ICs that uses the Filed effect transistor in the design. TTL stands for Transistor transistor logic. It is a classification of integrated circuits. The name is derived from the use of two bipolar junction transistors or BJT in the design of each logic gate. TTL chips tend to consume a lot more power compared to CMOS chips, especially at rest. As we know that the power consumption of a CMOS chip can vary depending on a few factors. Here this article gives the difference between CMOS and TTL to better understand this topic.
Related article: NMOS Vs CMOS
The main key difference between CMOS and TTL are listed below:
CMOS Vs TTL logic:
- CMOS stands for Complimentary Metal-oxide Semicodictor while in TTL stands for Transistor-Transistor Logic.
- CMOS circuit uses a field-effect transistor by connecting NMOS and PMOS, while the TTL circuit uses a bipolar junction transistor.
- The design of the CMOS can be considered to be very simpler as compared to the TTL.
- The longer rise and fall times of the CMOS can make this more energy-efficient as compared to the TTL.
- CMOS is to be weaker than TTL when it is at rest.
- CMOS components are generally more expensive when compared to TTL components, nit on system level, the CMOS chip are less expensive as there are smaller in size as compared to the TTL chips.
- A single logic gate in a CMOS chip can consist of as little as two FETs while a logic gate in a TTL chip consists of a substantial number of a part as extra components like resistors are needed.
- CMOS circuit is used in NAND-NOR gates while the basic gate use in standard TTL are NANA gates.
- There are substantial differences in the voltage level range for both. For TTL it is 4.75 to 5.25 V while for the CMOS it ranges between 0 to 1/3 VDD at a lower level and 2/3 VDD to VDD at high levels.
- Fan out of standard loads that can be connected to the output of the gate under normal for TTL is while it is 50 for CMOS circuit.
- CMOS circuits have better noise immunity than TTL circuits.
- The electromagnetic disruptions CMOS circuit components are more sensitive as compared to the TTL logic components.
- CMOS chips will be more likely to get damaged easily as compared to the TTL.
- The power consumption of CMOS can increase faster as compared to TTL whenever needed.
- A single gate in a CMOS chip can consume around 10nW while an equivalent gate on a TTL chip is consumed around 10mW of power.
- There are propagation delays present in both, On average the propagation delays of TTL are usually on 10nS whereas the propagation delays for the CMOS lay between 20 to 50 ns.
- CMOS technology and its circuit are more economical and preferred more as compared to TTL logic.
- CMOS is more susceptible to damage from electrostatic discharge than TTL components.
- The number of standard inputs that can be connected to the gate is the fan which is approximately 12-14 for the TTL and for the CMOS it is 10 only.
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Difference between CMOS and TTL?
And if A, B have one of the inputs is low0.8V, the voltage of the emitter E of T1 is pulled down, T1, 2, 5 are turned off, T4 is turned on, and the output is high.
D1 and D2 play a clamping role, limiting the current to protect the device.
Common types:
The 74 series that we commonly use now are TTL devices, and his level is judged to be the TTL level as the standard. In addition, there are the following types: high-speed H-TTL, low-power L-TTL, Schottky S-TTL, low-power Schottky LS-TTL
CMOS
Complementary symmetryIt is because both N-type MOS and P-type MOS appear in the circuit in the device.
Input Voltage Characteristics:Supply voltage: 3-18V
Low: 0.3*VCC High: 0.7*VCC
Output Voltage Characteristics:
Low: 0.1*VCC High: 0.9*VCC
Common series:
74HC High Speed CMOS, 74HCT TTL Compatible High Speed CMOS, 74BCT Bipolar Compatible TTL
(BiCMOS: the field effect transistor is used as the pre-stage and the intermediate stage; the triode is used as the output stage)
CMOS vs TTL comparison:
①TTL is a bipolar current control device, CMOS is a unipolar voltage control device
②The power supply voltage is different, TTL commonly used 5V power supply, CMOS: 5V, 3.3V, 2.4V, 1.8V
③TTLWeak anti-interference ability,Small noise margin, mainly because the CMOS logic level range is wide, the distance between the high-level threshold interval and the low-level interval is large, and the anti-interference ability is strong; butCMOSdevicehigh input impedance, easy to capture interference, noisy. But CMOS output impedance is low, in the range of KΩ;The unused input pins of CMOS devices must be grounded or fixed at a fixed level (that is, pay attention to electrostatic protection), while the pins of TTL devices are left floating and default to a high level.
④TTL power consumption is large, CMOS power consumption is low, static power consumption is almost no, and level switching has large current.
⑤TTL devices work fast, with a transmission delay of 5~10ns; cmos transmission delay of 25~50ns.
mutual drive analysis
Comparing the input and output levels of the two, it is obvious that TTL cannot directly drive CMOS devices, while the latter can directly drive the former; therefore, TTL driving CMOS requires a pull-up resistor on the periphery, and the VCC of TTL is connected to a resistor, so the high-level driving ability is very high. Small.