选择正确的电平转换方案英文

frm[版主]注册：2004-11-12 10:06:06可用积分：229全部积分：229等级：☆新年到，给各位拜年了！！！祝大家新年里，事业精进，财源滚滚！选择正确的电平转换方案原著：TI Corp --Application Report SCEA035A翻译：frm1. 简介在今天的电子电路系统中电压电平的转换基本成为了必须。

例如：一个ASIC的供电为VccA，而I/O器件的供电为VccB。

为了使它们之间正常通信，就需要一个如图1的电平转换（level－translation）方案。

输入电平限值和器件的输出电平主要根据器件采用的工艺技术和供电。

图2显示了不同的供电和元件技术的限值范围。

为了成功的实现两个器件的接口，一定要保证以下的条件：■驱动器件的Voh必须大于接收器件的Vih■驱动器件的Vol必须小于接收器件的Vil■驱动器件的输出电压范围不能超过接收器件的可容忍的I/O电压范围2. 双电源电平转换器件（Dual-Supply Level Translators）2.1 特性双电源的器件是为了满足两类总线或不同供电器件之间的异步通讯的。

这类器件采用双电源：VccA为A端（A side）供电，VccB为B端供电。

对于数据从A到B或B到A都能传输的双向的电平转换器件，方向取决于输入pin DIR的逻辑电平。

如果器件有OE控制，在OE有无效时A端和B端的总线隔离。

TI的双电源器件有各种位宽的应用并几乎覆盖了当前出现的全部的供电应用。

这些器件灵活，易用并能实现双向转换，对于许多电平转换的应用都是理想的选择（译者注：强！）。

它们的电流驱动能力可以使其适合长线及重载的应用。

SN74AVCB324245是一种32位双电源电平转换器件（由四组8位端口组成）。

图3显示了SN74AVCB324245的1.8V转3.3V的一个端口，同时另一个端口实现3.3V到1.8V的转换。

双电源器件的优点：●可以在不同电压结点间灵活的转换●具有电流驱动的能力●具有不同的位宽2.2 产品列表表1汇总了TI的双电源产品。

nmos的电平转换电路英文回答：A level shifting circuit using an NMOS transistor is commonly used to convert voltage levels in digital circuits. It allows signals with different voltage levels to communicate with each other.The basic idea behind an NMOS level shifting circuit is to use the NMOS transistor as a switch to connect or disconnect the input and output voltage levels. When the input voltage is high enough to turn on the NMOS transistor, the output voltage will be pulled down to a low level. On the other hand, when the input voltage is low, the NMOS transistor will be turned off, allowing the output voltageto be pulled up to a high level.Let's take an example to illustrate how an NMOS level shifting circuit works. Suppose we have a digital circuit operating at 3.3V and we want to interface it with anothercircuit operating at 5V. We can use an NMOS level shifting circuit to achieve this.In this example, the 3.3V digital circuit is connected to the gate of the NMOS transistor, and the 5V circuit is connected to the drain of the NMOS transistor. When the input signal from the 3.3V circuit is high, it turns on the NMOS transistor, allowing the 5V circuit to be pulled down to a low level. When the input signal is low, the NMOS transistor is turned off, allowing the 5V circuit to be pulled up to a high level.This level shifting circuit can be used in various applications, such as interfacing different voltage level devices, level shifting in I2C or SPI communication, and voltage level translation in microcontrollers.中文回答：NMOS电平转换电路常用于数字电路中，用于转换不同电平的信号，使其能够相互通信。

应用mosfet lowside driver 的电平变换设计
设计MOSFET低侧驱动电平变换可以按照以下步骤进行：
1. 选择合适的MOSFET型号：根据需要驱动的负载电流和电压，选择适当的MOSFET型号。

确保MOSFET的额定电流和电压能满足设计需求。

2. 确定输入电平：根据控制电路的输出电平确定输入电平（例如5V或
3.3V），这取决于你的控制电路。

3. 设计电平转换电路：为了将输入电平（如5V或3.3V）转换为驱动MOSFET 所需的高电平（一般为12V或15V），你可以使用电平转换电路。

3.1 使用电平转换电路，例如使用逻辑电平转换器或门电路，选择合适的部件和电路拓扑。

3.2 确保电平转换电路能提供足够的电流和速度以快速充放电MOSFET的输入电容。

4. 添加保护电路：根据需要，添加保护电路来保护MOSFET和其他电路元件，例如过电流保护、过温保护等。

5. 选择适当的驱动电路：根据MOSFET的特性和需求，选择合适的驱动电路。

有许多驱动电路可供选择，包括单极性和双极性驱动电路。

6. 进行电路仿真和测试：在实际应用之前，进行电路仿真和测试以确保电路的性能和可靠性。

总结：在设计MOSFET低侧驱动电平变换时，需要针对你的具体需求选择适当的MOSFET、设计电平转换电路、添加保护电路并选择适当的驱动电路。

最后进行电路仿真和测试以验证设计的正确性和可靠性。

电平转换精要-输出信号应有对应电平的输入信号Gene Warzecha, 应用工程经理Maxim公司在电子设计中，电平转换器能使I/O电压不同的器件建立通信。

多年前，I/O的电压通常是匹配的，因为大多数处理器和逻辑器件的工作电压都是5V。

当3.3V电压的器件出现后，它们也可以兼容5V电压。

但现在，伴随着高级工艺的发展，电子设计要能兼容许多更低的I/O电压。

芯片设计者能运用特殊的设计技术使I/O的电压“升高”，但是这些技术会降低生产量，降低品质，增加功耗。

此外，处理器或者其他器件需要由不同的电源供电，每个电源都要兼顾其应用和特殊的I/O电压。

因此，受器件设计差别和多个供电电源的影响，需要相互通信的两个器件可能不能直接通信，因为每个器件有不同的工作电压。

而逻辑电平转换器可以帮助解决这个问题。

理想的逻辑电平转换器（LLT）能在1Hz至1GHz之间正常工作，驱动漏级开路信号像驱动COMS推挽信号一样容易，也能很轻松的驱动长电缆。

但是逻辑电平转换器不是理想器件，一定存在功能上的妥协，因此电平转换器供应商会提供各种样式的转换器以满足不同种类的应用。

逻辑电平转换器基础一个主动双向电平转换器有两种基本组成结构，其中一种如图1所示。

通过管（Pass FET，下文同）的每一边都有一个上拉电阻，门级连接到V bias（通常是V cc1和V cc2中较低的那个电压）。

如果任何一个I/O电压（V i或者V o）连接到地电平，这会使正电压V gs打开FET，同时驱动另一侧I/O电压降到地电平。

如果没有I/O电压为低（两个都悬空），由于上拉电阻的作用，I/O的电压为各自的供电电压（V i或者V o）。

关于这个电路的一些重要结论：●输出信号的下降时间（fall time）主要由驱动器的强度，通过管的导通电阻和信号线的寄生电容决定。

●输出信号的上升时间（rise time）主要由输出端的上拉电阻和信号线的寄生电容决定-假设通过管是即刻关闭的（事实并非如此，为方便此处讨论我们做此假设）●输出端低电平电压总比输入端的低电平电压高，这是欧姆定律决定的。

项目过程中，经常出现电平不匹配的问题，就需要进行电平匹配。

本文介绍几种常用的低速信号电平匹配方法1、 三极管+上拉电阻法，如下图是VCC1V8转VCC3V3：RESET_REQ_B 信号是CPU 发出的信号，电平为1.8V ，而APX811的MR_N 信号高电平要求3.3V ，故通过一个NPN 三极管进行电平转换。

如上图，当RESET_REQ_B 为high 的时候，三极管关断，此时MR_N 电平为上拉VCC_3V3，当RESET_REQ_B 为low 的时候，三极管导通，MR_N 信号为低，实现了电平转换。

但运用此电路的时候，一定要正确使用三极管，如下是某项目中设计的一个3.3V 转1.8V 的电平转换电路。

实际测量过程中发现不管BT_RSTn 电平如何变化，BT_RST_N 的电平都是2.5V ，该电路是由NPN 三极管时序1.8V 转3.3V ，由于PN 结的原因，BC 之间导通，三级管的基级电压VCC_3V3通过BC 之间的的PN 结直接到集电极，查看规格书，PN 结电压大约在0.8V 左右，故集电极BT_RST_N 的电压一直为2.5V 左右。

NPN 三极管使用中，一定要保证VC>VB ，如下为三极管工作的四种状态。

2、 电阻分压法RESET_REQ_B5RESET54.7KohmBT_RSTn10电阻分压法只能用于高电平转低电平的电路中，如上中3.3V 转1.8V(VDDS)电路，可以通过电阻分压法进行电平转换。

如下是修改后的电路：3、 使用串阻方法该方法也只适用于高电平转低电平电路，如下：高逻辑电平驱动低逻辑电平时，可串联50Ω~330Ω电阻实现电平的转换，串联电阻的阻值需要根据I/O 口动态电流计算。

4、 使用OD/OC 门芯片+上拉电阻如下图，采用了一个输出为OD 门的buffer 芯片，实现1.8V 转1.35V 的电平转换5、 电平转换芯片专用电平转换芯片主要用于信号速率较高，对信号要求延时等由要求的电路中，如下是MDC/MDIO （SMI ）使用的电平转换芯片。

CMOS电平转换电路详解COMS集成电路是互补对称金属氧化物半导体（Compiementary symmetry metal oxide semicoductor）集成电路的英文缩写，电路的许多基本逻辑单元都是用增强型PMOS晶体管和增强型NMOS管按照互补对称形式连接的，静态功耗很小。

COMS电路的供电电压VDD范围比较广在+5~+15V均能正常工作，电压波动允许10，当输出电压高于VDD-0.5V时为逻辑1，输出电压低于VSS+0.5V（VSS为数字地）为逻辑0。

CMOS电路输出高电平约为0.9Vcc，而输出低电平约为0.1Vcc.当输入电压高于VDD-1.5V时为逻辑1，输入电压低于VSS+1.5V（VSS为数字地）为逻辑0。

TTL电平信号被利用的最多是因为通常数据表示采用二进制规定，+5V等价于逻辑1，0V 等价于逻辑0，这被称做TTL（晶体管-晶体管逻辑电平）信号系统，这是计算机处理器控制的设备内部各部分之间通信的标准技术。

标准TTL输入高电平最小2V，输出高电平最小2.4V，典型值3.4V，输入低电平最大0.8V，输出低电平最大0.4V，典型值0.2V（输入H》2V，输入L《0.8V;输出H 》2.4V（3.4V），输出L《0.4V（0.2V）。

CMOS电平是数字信号还是模拟信号？CMOS电平是数字信号，COMS电路的供电电压VDD范围比较广在+5--+15V均能正常工作，电压波动允许10，当输出电压高于VDD-0.5V 时为逻辑1，输出电压低于VSS+0.5V（VSS为数字地）为逻辑0，一般数字信号才是0和1 。

cmos电平转换电路1、TTL电路和CMOS电路的逻辑电平VOH：逻辑电平1 的输出电压VOL：逻辑电平0 的输出电压VIH ：逻辑电平1 的输入电压VIH ：逻辑电平0 的输入电压TTL电路临界值：。

常用的电平转换方法及注意事项１：常用的电平转换方案(1) 晶体管+上拉电阻法就是一个双极型三极管或 MOSFET，C/D极接一个上拉电阻到正电源，输入电平很灵活，输出电平大致就是正电源电平。

(2) OC/OD 器件+上拉电阻法跟 1) 类似。

适用于器件输出刚好为 OC/OD 的场合。

(3) 74xHCT系列芯片升压(3.3V→5V)凡是输入与 5V TTL 电平兼容的 5V CMOS 器件都可以用作 3.3V→5V 电平转换。

——这是由于 3.3V CMOS 的电平刚好和5V TTL电平兼容（巧合），而 CMOS 的输出电平总是接近电源电平的。

廉价的选择如 74xHCT(HCT/AHCT/VHCT/AHCT1G/VHCT1G/...) 系列 (那个字母 T 就表示 TTL 兼容)。

(4) 超限输入降压法(5V→3.3V, 3.3V→1.8V, ...)凡是允许输入电平超过电源的逻辑器件，都可以用作降低电平。

这里的"超限"是指超过电源，许多较古老的器件都不允许输入电压超过电源，但越来越多的新器件取消了这个限制 (改变了输入级保护电路)。

例如，74AHC/VHC 系列芯片，其 datasheets 明确注明"输入电压范围为0~5.5V"，如果采用 3.3V 供电，就可以实现5V→3.3V 电平转换。

(5) 专用电平转换芯片最著名的就是 164245，不仅可以用作升压/降压，而且允许两边电源不同步。

这是最通用的电平转换方案，但是也是很昂贵的 (俺前不久买还是￥45/片，虽是零售，也贵的吓人)，因此若非必要，最好用前两个方案。

(6) 电阻分压法最简单的降低电平的方法。

5V电平，经1.6k+3.3k电阻分压，就是3.3V。

(7) 限流电阻法如果嫌上面的两个电阻太多，有时还可以只串联一个限流电阻。

某些芯片虽然原则上不允许输入电平超过电源，但只要串联一个限流电阻，保证输入保护电流不超过极限(如 74HC 系列为 20mA)，仍然是安全的。

电平转换方案1. 引言在电子设备和电路设计中，电平转换是一个常见的问题。

不同设备或电路之间可能采用不同的电平标准，如5V、3.3V、2.5V等，为了确保正确的信号传输和兼容性，需要进行电平转换。

本文将介绍电平转换的背景知识、常见的电平转换方案以及各种方案的优缺点。

2. 背景知识2.1 电平标准不同设备或电路常采用不同的电平标准，主要包括：•TTL（Transistor-Transistor Logic）电平：常见的电压标准为0V~5V，适用于许多数字电路。

•CMOS（Complementary Metal Oxide Semiconductor）电平：常见的电压标准为0V3.3V或0V5V，适用于许多数字电路。

•LVCMOS（Low Voltage CMOS）电平：常见的电压标准为0V1.8V或0V3.3V，适用于低功耗数字电路。

•LVTTL（Low Voltage TTL）电平：常见的电压标准为0V~3.3V，适用于低功耗数字电路。

2.2 电平转换的目的电平转换主要是为了实现不同电平标准之间的互联互通，确保信号能够正确传输。

常见的应用场景包括：•不同电平标准的设备之间的通信。

•不同电平标准的外设与主控芯片之间的连接。

3. 常见的电平转换方案3.1 使用电平转换芯片常见的电平转换方案之一是使用专门的电平转换芯片。

这些芯片通常包含了输入电平和输出电平之间的转换电路，能够在不同电平标准之间实现电平的转换。

优点：•专用芯片，性能稳定可靠。

•可以实现多个通道的电平转换。

•部分芯片提供了自动方向控制功能，简化了硬件设计。

缺点：•芯片成本较高。

•大部分芯片需要外部电源供电。

•需要占用额外的PCB空间。

3.2 使用电平转换电路除了使用专用的电平转换芯片，也可以使用离散的电平转换电路来实现电平转换。

这些电路通常由离散的电阻、晶体管等器件组成，在具有一定电路设计能力的情况下，可以实现相对简单的电平转换功能。

优点：•成本较低，只需要少量的离散器件。

二个三极管组成电平转换英文回答：To convert voltage levels, I would use a circuit consisting of two transistors. Transistors are electronic devices that can amplify or switch electronic signals. In this case, we will use them to switch between different voltage levels.The first transistor, called the input transistor, is connected to the input voltage source. It acts as a switch, allowing current to flow through it when a certain voltage level is reached. When the input voltage is low, the input transistor is off and no current flows through it. When the input voltage is high, the input transistor turns on and allows current to flow.The second transistor, called the output transistor, is connected to the output voltage source. It also acts as a switch, controlling the flow of current to the outputvoltage source. The output transistor is connected to the input transistor in such a way that when the inputtransistor is on, the output transistor is off, and vice versa.By connecting the input and output transistors in this way, we can achieve voltage level conversion. When theinput voltage is low, the input transistor is off, and the output transistor is on, allowing current to flow from the output voltage source. This results in a low output voltage. When the input voltage is high, the input transistor turns on, turning off the output transistor and preventingcurrent from flowing to the output voltage source. This results in a high output voltage.Let me give you an example to illustrate how thiscircuit works. Suppose we have an input voltage of 3V andan output voltage of 5V. When the input voltage is below 3V, the input transistor is off, and the output transistor is on, allowing current to flow from the 5V source. Thisresults in a low output voltage of 0V. When the input voltage is above 3V, the input transistor turns on, turningoff the output transistor and preventing current from flowing to the 5V source. This results in a high output voltage of 5V.中文回答：要实现电平转换，我会使用由两个三极管组成的电路。

逻辑电平转换（英文）Maxim > App Notes > MICROCONTROLLERSKeywords: logic-level translation, MAX1840, MAX1841, MAX3001, MAX3370-MAX3393, MAX8860, MAX8867Jul 21, 2004 APPLICATION NOTE 3007Logic-Level TranslationAbstract: Logic level translation techniques and pitfalls - and Maxim solutions.Electronic design has changed considerably since the days when TTL and 5V CMOS were the dominant standards for logic circuits. The increasing complexity of modern electronic systems has led to lower voltage logic, which in turn can cause incompatibility between input and output levels for the logic families within a system. It is not unusual, for example, that a digital section operating at 1.8V must communicate with an analog subsection operating at 3.3V. This article examines the basics of logic operation and considers,primarily for serial-data systems, the available methods for translating between different domains of logic voltage.The Need for Logic-Level TranslationThe growth of digital ICs that feature incompatible voltage rails, lower V DD rails, or dual rails for V CORE and V I/O has made the translation of logic levels necessary. The use of mixed-signal ICs with lower supply voltages that have not kept pace with those of their digital counterparts also creates the need for logic-level translation. Translation methods vary according to the range of voltages encountered, the number of lines to be translated (e.g., a 4-line Serial Peripheral Interface (SPI?) versus a 32-bit data bus),and the speed of the digital signals. Many logic ICs can translate from high to low levels (such as 5V to 3.3V logic), but fewer can translate from low to high (3.3V to 5V). Level translation can be accomplished with single discrete transistors or even with a resistor-diode combination, but the parasitic capacitance inherent in these methods can reduce the data-transfer rate.Although byte-wide and word-wide level translators are available, they are not optimal for the < 20Mbps serial buses discussed in this article (SPI, I2C, USB, etc.). Thus, translators that require large packages with high pin counts and an I/O-direction pin are not meant for small serial and peripheral interfaces.The Serial Peripheral Interface consists of the unidirectional control lines data in, data out, clock, and chip select. Data in and data out are also known as master in, slave out (MISO) and master out, slave in (MOSI). SPI can be clocked in excess of 20Mbps, and is driven by CMOS push-pull logic. As SPI is unidirectional, translation in both directions on the same signal line is unnecessary. This makes level translation simpler, because you can employ simple techniques involving resistors and diodes (Figure 1) or discrete/digital transistors (Figure 2).Figure 1. A resistor-diode topology is one alternative technique to translation in both directions on the same signal line.Figure 2. Using discrete/digital transistors is another alternative to bidirectional translation.The I2C, SMBus?, and 1-Wire?, interfaces are all bidirectional, open-drain I/O topologies. I2C has three speed ranges: standard mode at ≤ 100kbps, fast mode at ≤ 400kbps, and high-speed mode at ≤ 3.4Mbps. Level translation for bidirectional buses ismore difficult, because one must translate in both directions on the same data line. Simple topologies based on resistor-diode and single-stage-transistor translators with open collector or drain do not work because they are inherently unidirectional.Unidirectional High- to Low-Level Translation—Input Overvoltage ToleranceTo translate from higher to lower logic levels, IC manufacturers produce a range of devices that are said to tolerate overvoltage at their inputs. A logic device is defined as input-overvoltage protected if it can withstand (without damage) an input voltage higher than its supply voltage. Such input-protected devices simplify the task of translating from higher- to lower-V CC logic while increasing the signal-to-noise margin.Overvoltage-tolerant inputs, for example, allow a logic device to cope with logic levels of 1.8V and higher while powered from a 1.8V supply. Devices in the LVC logic family, which are mostly input-overvoltage protected, work well in applications requiring high-to-low translations. The opposite situation of low-to-high translation is not as easy. It may not be feasible to generate higher voltage logic-level thresholds (V IH) from lower voltage logic.When designing a circuit for which connectors, high fanout, or stray load capacitance produce a high capacitance load, you should remember that for all logic families, reducing the supply voltage also decreases the drive capability. An exception occurs between 3.3V CMOS or TTL (LV, LVT, ALVT, LVC, and ALVC) and 5V standard TTL (H, L, S, HS, LS, and ALS). In these logic families, the 3.3V and 5V logic activation points (V OL, V IL, V IH, andV OH) match each other.Mixed High-Low and Low-High TranslationApplications like the SPI bus require a mixture of high-low and low-high translation. Consider, for example, a processor at 1.8V and a peripheral at 3.3V. Though it is possible to mix techniques as described above, a single chip such as the MAX1840, MAX1841, or MAX3390 can implement the necessary translation by itself (Figure 3).Figure 3. This diagram shows an example of an IC level translator with an SPI/QSPI?/MICROWIRE? interface that can implement the necessary mixture of high-low and low-high translation.Other systems, such as I2C and 1-Wire buses, require logic translation in both directions. Simple topologies, based on a single transistor with open collector or drain, do not work in a bidirectional bus because they are inherently unidirectional.Bidirectional Transceiver MethodsFor the larger byte- and word-wide buses where WR and RD signals already exist, one method for transferring data across the voltage levels is a bus switch such as the 74CBTB3384. Such devices are typically optimized for operation between 3.3V and 5V. For smaller 1- and 2-wire buses, this approach raises two issues. Firstly, it requires a separate enable pin to control the direction of data flow, and this ties up valuable port pins. Secondly, it requires large ICs that take up valuable board space.All techniques have their pros and cons. Nonetheless, designers need a universal device that works across all translation levels, enables mixed low-to-high and high-to-low logic transitions, and includes unidirectional and/or bidirectional translation. A next-generation bidirectional level shifter (the MAX3370 in the MAX3370–MAX3393 family of ICs) fulfills those needs while overcoming some of the problems associated withalternative approaches. The MAX3370, which implements a transmission-gate method of level translation (Figure 4), relies on external output drivers to sink current, whether they operate in a low-voltage or higher voltage logic domain. That capability enables the device to work with either open-drain or push-pull output stages. The relatively low on-resistance of a transmission gate (less than 135?), moreover, limits the speed of operation much less than the series resistor of Figure 1.Figure 4. The MAX3370 implements a transmission-gate method of level translation.The design in Figure 4 offers two other advantages. Firstly, for open-drain topologies, the MAX3370 includes10k? pull-up resistors paralleled by a "speed-up" switch. This minimizes the need for external pull-up resistors while reducing the RC time-constant ramp associated with traditional open-drain topologies. Secondly, theMAX3370's tiny SC70 package also conserves valuable board space.Solving the Speed ProblemRC time constants limit the effective data rate for most other open-drain approaches (Figures 5 and 6). The MAX3370 IC family includes a patented speed-up scheme that actively pulls up rising edges, thereby minimizing the effect of capacitive loads as illustrated in Figures 7, 8, and 9. When the input goes above a predefined threshold, the device actively pulls up the rising edge, thereby minimizing any skew caused by external parasitic components. That capability can allow data rates as high as 20Mbps for signals produced by a push-pull driver. The speed of signals from open-drain drivers tends to be slower. As for other open-drain topologies, however,you can improve their speed by adding external pull-up resistors.Figure 5. The scope plot of single FET open-drain output at 20kHz shows a limited effective data rate due to RC time constants.Figure 6. Scope plots of a dual-transistor transceiver translating 1.8V to 5V at 400kHz (a) and at 100kHz (b) illustrate limited effective data rates.Figure 7. A scope plot of MAX3370 output with a translation of 1.8V to 5V at 400kHz shows minimized capacitive load effects.Figure 8. This scope plot of the MAX3370 output at 400kHz with 4.7k?pullup resistors shows the minimized effect of capacitive loads.Figure 9. This plot shows an example of rail-to-rail driving of the output from a MAX3370 high-speed test circuit. Solving the Universal Voltage ProblemAn application ideally requires a single component that can translate between any two logic levels at any speed. The ICs in the MAX337x family are designed for logic levels as low as 1.2V and as high as 5.5V. Consequently, this single component can provide the level translation required in most cases, without needing to select a logic device for each level-translator requirement.Formerly, the need for low-to-high and high-to-low translations in the same circuit could be met only with separate chips. Now the bidirectional and topology-independent features (push-pull or open-drain) of a single chip from the MAX337x family solve both problems. The MAX3370 is a single-line, universal logic-level translator. For translating a larger number of I/O lines, consult the devices listed in Table 1.。

常用的电平转换方案1，TTL电平(什么是TTL电平)：输出高电平>2.4V,输出低电平<0.4V。

在室温下，一般输出高电平是3.5V，输出低电平是0.2V。

最小输入高电平和低电平：输入高电平>=2.0V，输入低电平<=0.8V，噪声容限是0.4V。

2，CMOS电平：1逻辑电平电压接近于电源电压，0逻辑电平接近于0V。

而且具有很宽的噪声容限。

3，电平转换电路：因为TTL和COMS的高低电平的值不一样（ttl 5v<＝＝>cmos 3.3v），所以互相连接时需要电平的转换：就是用两个电阻对电平分压，没有什么高深的东西。

哈哈4，OC门，即集电极开路门电路，OD门，即漏极开路门电路，必须外界上拉电阻和电源才能将开关电平作为高低电平用。

否则它一般只作为开关大电压和大电流负载，所以又叫做驱动门电路。

5，TTL和COMS电路比较：1）TTL电路是电流控制器件，而coms电路是电压控制器件。

2）TTL电路的速度快，传输延迟时间短(5-10ns)，但是功耗大。

COMS电路的速度慢，传输延迟时间长(25-50n s),但功耗低。

COMS电路本身的功耗与输入信号的脉冲频率有关，频率越高，芯片集越热，这是正常现象。

3）COMS电路的锁定效应：COMS电路由于输入太大的电流，内部的电流急剧增大，除非切断电源，电流一直在增大。

这种效应就是锁定效应。

当产生锁定效应时，COMS的内部电流能达到40mA以上，很容易烧毁芯片。

防御措施：1）在输入端和输出端加钳位电路，使输入和输出不超过不超过规定电压。

2）芯片的电源输入端加去耦电路，防止VDD端出现瞬间的高压。

3）在VDD和外电源之间加线流电阻，即使有大的电流也不让它进去。

4）当系统由几个电源分别供电时，开关要按下列顺序：开启时，先开启COMS电路得电源，再开启输入信号和负载的电源；关闭时，先关闭输入信号和负载的电源，再关闭COMS电路的电源。

6，COMS电路的使用注意事项1）COMS电路时电压控制器件，它的输入总抗很大，对干扰信号的捕捉能力很强。

应用报告ZHCA047–2004年6月选择正确的电平转换解决方案Prasad Dhond摘要电源电压持续迁移到较低的节点以支持当前的低功耗高性能应用。

虽然某些器件可以在较低的电源节点运行，但是其它器件可能不具有这种能力。

为了在这些器件之间实现切换兼容性，每个驱动器的输出必须与其驱动的接收器的输入兼容。

用于实现这些器件的互相连接的电平转换方案有很多。

根据应用的不同需要，某种方法可能比其它方法更适合。

本应用报告概述了用于转换逻辑电平的方法和产品，并列出了每种德州仪器(TI)电平转换解决方案的优缺点。

关键字：双电源、分离轨、电平转换、电平转换器、混合电压、T45、T245、4245、3245、漏极开路、过压容限、TTL、CMOS、TVC、CB3T、CBTD主题页1简介*V CC A not equal to V CC BV CCV CCV CCV CC V CC V CC V OHV IHV TV ILV OL GND5 V 4.44 V0.7 y V CC 0.5 y V CC 0.3 y V CC 0.5 V 0 VV IH V IL GNDV OH V IH V T V IL V IL V OL GND5 V2.4 V 2 V1.5 V 0.8 V0.4 V 0 VV OH V IH V T V OL GND3.3 V2.4 V 2 V 1.5 V 0.8 V 0.4 V 0 V2.5 V 2.0 V 1.7 V0.7 V 0.4 V 0 VV OH V IH V IL V OL GND1.8 V V CC−0.45 V0.65y V CC 0.35y V CC0.45 V0 VV OH V IHV IL V OLGND1.2 V 0.65y V CC 0.35y V CC0 VV CC 1.5 V 0.65y V CC0.35y VCC0 V V IH V IL GND5−V CMOS 5−V TTL 3.3−V LVTTL 2.5−V CMOS 1.8−V CMOS 1.5−V CMOS 1.2−V CMOS2双电源电平转换器简介在目前大多数电子系统中，对电压电平转换的需求非常普遍。

5v转24v 脉冲电平转换电路英文版5V to 24V Pulse Level Conversion CircuitIn electronics, level conversion is a crucial technique that allows different devices or circuits to communicate effectively. One such conversion is the transition from a low voltage level, typically 5V, to a higher voltage level, such as 24V. This process is particularly useful in scenarios where a low-voltage control signal needs to control a high-voltage device or system.The pulse level conversion circuit, specifically designed for this purpose, converts the input pulse signals from a lower voltage to a higher voltage. This conversion is achieved using a combination of transistors, resistors, and capacitors. The transistors act as switches, allowing the circuit to switch between the two voltage levels. The resistors and capacitors control the flow of current and maintain stability in the circuit.In a 5V to 24V pulse level conversion circuit, the input signal, typically a 5V pulse, triggers the transistors to switch on, allowing the flow of current from the higher voltage source (24V) to the output. When the input pulse ends, the transistors switch off, cutting off the flow of current and maintaining the output at the higher voltage level.This conversion circuit is highly efficient and can handle fast pulse signals, making it suitable for various applications such as motor control, relay activation, and other high-voltage systems. It is crucial to design the circuit carefully to ensure reliable and efficient performance.中文版5V转24V脉冲电平转换电路在电子学中，电平转换是一项至关重要的技术，它允许不同的设备或电路进行有效的通信。

nmos的电平转换电路英文回答：NMOS level shifting circuit is a circuit used to convert voltage levels from one logic level to another using NMOS transistors. It is commonly used in digital systems where different voltage levels are used for different logic levels.The basic principle of an NMOS level shifting circuitis to use a pull-up resistor and a NMOS transistor to create a voltage divider. The pull-up resistor is connected between the output and the positive power supply voltage, while the NMOS transistor is connected between the output and ground. By controlling the gate voltage of the NMOS transistor, the output voltage can be shifted to the desired logic level.For example, let's say we have a digital system that operates at 3.3V logic level, but we need to interface itwith another system that operates at 5V logic level. We can use an NMOS level shifting circuit to convert the 3.3Vlogic level to 5V logic level.In this case, we can connect a pull-up resistor between the output and the 5V power supply, and connect an NMOS transistor between the output and ground. By applying a voltage higher than the threshold voltage of the NMOS transistor to its gate, the transistor will turn on andpull the output voltage close to ground, resulting in a logic low level. On the other hand, by applying a voltage lower than the threshold voltage of the NMOS transistor to its gate, the transistor will turn off and the pull-up resistor will pull the output voltage close to the 5V power supply, resulting in a logic high level.This NMOS level shifting circuit allows us to interface the 3.3V logic level system with the 5V logic level system, ensuring proper communication between the two systems.中文回答：NMOS电平转换电路是一种使用NMOS晶体管将电压从一种逻辑电平转换为另一种逻辑电平的电路。

分享几种常用的电平转换方案前段时间在设计NB-IOT模块与STM32的硬件通讯时用到了电平转换。

当主控芯片引脚电平与外部连接器件电平不匹配的时候就需要用电平转换电路来进行转换。

这几乎是每一个电子工程师都会遇到的一个问题。

今天我就总结一下几种常用的电平转换方案，希望对大家有所帮助。

1.使用电平转换芯片这可能是所有方案里面最稳定可靠省事的了，给转换芯片两侧供需要转换的两个电源，然后在芯片的输入输出接上需要转换的输入输出信号就OK了，所有转换部分都由芯片内部完成。

下图为德州仪器的TXB0108双向电平转换器。

TXB0108这种方案的优点很多，上面的这款转换器在VccA供电电压2.5V 以上的时候最高可以达到100Mbps，速度非常快。

除此之外还有驱动能力强、使用简单等优点。

当然缺点也是有的，最主要就是价格上毫无优势，在需要控制成本的项目上就很难使用了。

2.三极管或MOS管转换电平这是一种比较常用的方案，我所使用的NB-IOT模块的datasheet 上面就有推荐这种方案。

如下图所示，当TXD端为高电平时，NPN三极管处于截止状态，RXD端被上拉到其电源电压；当TXD端为低电平时NPN三极管导通，RXD端被拉低到低电平，完成电平转换。

三极管也可以使用MOS管替换。

这种方案最大的优点莫过于成本低廉，比第一种方案不知便宜了多少倍；再一个就是布局简单，可以根据电路板的尺寸进行合理布局。

这种方案的缺点也是很明显，就是速度有限制，上面提到的datasheet里面给出的数据是不适合波特率超过460800bps的应用。

3.使用电阻分压转换电平这种方案应该是最便宜的一种了，只使用了电阻这一种器件，如下图所示。

我们分析一下这个电路，当3.3V电平模块向右侧发送数据的时候只通过限流电阻，到达右侧时的电平在客户端的接收范围内。

当5V电平客户端向左侧发送数据时通过两个电阻分压，左侧接收端电压5V*2K/(1K+2K)≈3.3V。

3电平转换技术（原创实用版）目录1.电平转换的背景和原因2.LVPECL 和 CML 电平转换的原理3.LVPECL 到 CML 的直流耦合连接方式4.LVPECL 到 CML 的交流匹配方法5.CML 到 LVPECL 的交流匹配方法6.结论正文一、电平转换的背景和原因在电子通信系统中，不同系统之间的电压规格可能会有所不同，这导致在同一系统中的 0、1 电平表示的电压值在不同系统中可能有所差异。

为了实现不同系统之间的通信，需要进行电平转换。

电平转换技术的主要目的是将一个系统的电压信号转换为另一个系统可以识别的电压信号，以确保信号的准确传输。

二、LVPECL 和 CML 电平转换的原理LVPECL（Low Voltage PECL）和 CML（Current Mode Logic）是两种常见的电平转换技术。

LVPECL 是一种低电压、高电流的电平转换技术，主要用于高速信号传输。

CML 是一种基于电流模式的逻辑电平转换技术，具有较高的输入和输出阻抗。

这两种技术在电平转换方面有各自的优势，因此经常被用于不同系统之间的电平转换。

三、LVPECL 到 CML 的直流耦合连接方式在 LVPECL 和 CML 之间的直流耦合连接方式中，需要一个电平转换网络来实现两者之间的匹配。

这个电平转换网络的主要作用是匹配LVPECL 的输出与 CML 的输入共模电压。

为了保证 LVPECL 的输出经过衰减后仍能满足 CML 输入灵敏度的要求，需要使电平转换网络引入的损耗尽可能小。

此外，还要求从 LVPECL 端看到的负载阻抗近似为 50 欧姆。

四、LVPECL 到 CML 的交流匹配方法为了实现 LVPECL 到 CML 的交流匹配，需要在 LVPECL 的两个输出端各加一个到地的偏置电阻。

电阻值选取范围可以从 142 到 200 欧姆。

如果 LVPECL 的输出信号摆幅大于 CML 的接收范围，可以在信号通道上串一个 25 欧姆的电阻，此时 CML 输入端的电压摆幅变为原来的 0.67 倍。