In recent years, under the driving of Apple iPhone, the smartphone market has expanded. An important feature of portable products such as smartphones is more and more, which supports wider consumer demand. However, the operating voltages of portable products such as smartphones to support different functions are often different, such as baseband processors and application processor voltages are typically between 1.5V to 1.8V, and there are many outside The working voltage is typically 2.6 to 3.3V, such as the USIM card, Wi-Fi module, FM (FM) tuner module operating voltage is 2.8V, and the camera module is 2.7V.
Figure 1: Schematic diagram of logic level converter application
Therefore, there is an input / output voltage mismatch problem between different ICs and peripheral modules such as smartphones such as input / output voltage mismatches, so that these devices are communicated with the modules, requiring efficient logic voltage level conversion. The so-called logic level converter is connected to the IC and module or printed circuit board (PCB) of different operating voltages, providing system integration solutions.
Traditional logic level conversion method and its advantages
Table 1: Traditional logic level conversion method and advantages and disadvantages
Since transistor-transistor logic (TTL) and complementary metal oxide semiconductors (CMOS) are standard levels in logic circuits, TTL-CMOS input conversion is common due to the traditional logic level conversion method. This conversion method is simple, low cost, mainly for low levels to high conversion, and can also be used to convert high levels to low. This conversion method also has some shortcomings. Other conventional logic level conversion methods include overvoltage tolerance (OVT) voltage conversion, drain open circuit (OD) / active lower pulling conversion and discrete I2C conversion, etc., each has its own advantages and disadvantages, see Table 1.
Dual power logic level conversion and application
The power will be consumed in the logic level conversion. For example, in low to high conversion, in order to output a high logic level, the input voltage (Vin) is lower than Vcc, and the power supply current change (ΔICC) is always higher, so power consumption is also high. In order to solve the problem of high power consumption, a dual supply voltage (VCCA and VCCB) logic level converter can be used. When the logic power supply voltage (VL) is equal to VIN, the ΔICC is 0, thereby reducing power consumption.
Common Dual Power Logic Level Conversion includes one-way conversion, bidirectional conversion of the band direction control pins, automatically sensing two-way conversion (push-pull output) and automatic sensing bidirectional conversion for drain open circuit applications (such as I2C), etc. The structure is shown in Figure 2.
Figure 2: Schematic diagram of several dual power logic level converters
In these dual power logic level conversion methods, the principle of one-way logic level conversion is to provide A point to B-point conversion when output enable (OUTPUTENABLE,) is low, and when the output is enabled, A High-resistance (Hi-Z) is present between B, which is usually treated with an infinite resistance, which is equivalent to not being turned on. Common dual power-to-digital logic levels include NLSV1T34AMX1TCG, NLSV4T244Mutag, NLSV8T244Mutag, NLSV22T244Mutag, NLSV22T244Mutag, NLSV22T244Mutag, NLSV4T244Mutag, NLSV22T444Mutag, etc. Applications of these dual power supply-to-channel logic level converters include Universal Input Output (GPIO) ports, serial section (SPI) ports, and universal serial bus (USB) ports.
The working principle of the bidirectional logic level converter with directional control pins is that the pin and direction control (Direction, T /) pins provide a low level, providing B points to a point conversion; pins are low When the T / pin is high, it provides a point to B-point conversion; when the pin is high, the A point to the B point direction and the B point to the direction are in high resistance, which is equivalent to not picking up Pass. Ans Many Semiconductors will introduce a two-way logic level converter with directional control pins. Common applications for such converters are memory and I / O devices accessed in bytes (byte).
The working principle of the automatic sense of the two-way logic level converter (push-pull output) is: When the enable (EN) pin is low, the converter is in standby; the EN pin is high, I / O level When the converter is in steady state; the EN pin is high, the I / O level changes, the converter detects changes, and generates a pulse, I / O borrows P-channel MOSFET (PMOS) Faster. Typical automatic sensing direction bidirectional logic level converter (push-pull output) has NLSX3012Mutag, NLSX3013BFCT1G, NLSX4014Mutag, and NLSX4014Mutag, and NLSX3018Mutag, and NLSX3018Mutag, and NLSX3018Mutag, and NLSX3018Mutag. Common applications for such converters include universal asynchronous transceivers (UART), USB ports, 4-wire SPI ports, and 3-wire SPI ports.
The automatic sensing bidirectional logic level converter for drain open circuit applications (such as I2C) also includes three states: the EN pin is high, when NMOS is turned on, in operation, input terminal I / O level Dressing to the ground, that is, input low; the EN pin is high, the NMOS is in the working state, the output terminal I / O pulls up to VCC, that is, the input high level; EN pin When it is low, the converter is in standby. Typical automatic sensing bidirectional logic level converters for drain open applications (such as I2C) are NLSX4373Mutag, NLSX4348FCT1G, and NSLX4378BFCT1G, such as Ansian Semiconductors. Common applications for such converters include I2C bus, user identification module (SIM) card, single line (1-wire) bus, display module, secure digital input / output (SDIO) card, etc.
In the above-mentioned double power logic level converters, the automatic sensing converters and converters with directional control pins and converters with direction control pins have their advantages. The advantages of the automatic sensing converter are mainly reflected in minimizing the I / O lines of the microcontroller. It is a simple solution for asynchronous communication, and the disadvantage is a converter that costs above and the bandwidth lower than the direction control pin. . The converter advantage of the directional control pin is a simple solution for the commodity components. It is a simple solution for memory mapping I / O, which is a large number of microcontroller pins.
In the automatic sensing converter without the directional control pins, there is also an integrated scheme (such as NLSX3373) and discrete scheme (such as NTZD3154N). The integrated scheme NLSX3373 is a single IC, and it is estimated that the occupied circuit board (PCB) space is only 2.6mm2; discrete scheme NTZD3154N uses a double MOSFET and 4 01005 packages (ie 0402) resistance, estimated to occupy the total PCB total space of 3.3 MM2. The integrated scheme provides low power standby mode, and the discrete scheme does not provide high impedance / standby mode. The low pressure working characteristics, bandwidth and circuit characteristics of these two different programs are also different.
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Source: Wiku Electronic Market Network
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