* : Products list (parametric search)
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The information presented in this cross reference is based on TOSHIBA's selection criteria and should be treated as a suggestion only. Please carefully review the latest versions of all relevant information on the TOSHIBA products, including without limitation data sheets and validate all operating parameters of the TOSHIBA products to ensure that the suggested TOSHIBA products are truly compatible with your design and application.Please note that this cross reference is based on TOSHIBA's estimate of compatibility with other manufacturers' products, based on other manufacturers' published data, at the time the data was collected.TOSHIBA is not responsible for any incorrect or incomplete information. Information is subject to change at any time without notice.
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降压(5 V→3.3 V)和升压(3.3 V→5 V)电压转换可以通过使用具有容错功能的CMOS逻辑IC、单电源或双电源电平转换器(缓冲器类型)以及双电源总线开关。
以下是一个简例。
有关详细的选择方法,请参阅以下应用说明.
→ Tips for Selecting Level Shifters(Voltage Translation ICs) (PDF:2.62MB)
降压转换:
输入容限功能允许通过电平转换将较高电压转换为较低电压,例如从5 V至3.3 V。例如,输入容限功能允许将5 V电压施加至输入端而不消耗额外电流,即使VCC=0 V。(图 1)
对于使用CMOS逻辑IC的输入容限功能的降压转换,请确保最大低电平输入电压在VIL范围内。(表1)
表1:具有非TTL输入的典型CMOS逻辑IC的输入规格示例(74VHC240)
升压转换:
如果驱动IC的高电平输出电压(VOH)满足被驱动IC的高电平输入电压(VIH),即可实现较低电压至较高电压(例如,3.3 V至5 V)的电平转换,因为VOH几乎等于供电电压(VCC)。
由于典型CMOS逻辑IC的指定最小高电平输入电压(VIH)为VCC×0.7,当VCC=5 V时,VIH为3.5 V。因此,如果驱动IC的VOH为3.3V,则不满足被驱动IC的最小VIH。在这种情况下,请考虑使用具有TTL输入的CMOS逻辑IC。(图2)
表2显示了74HCT240的TTL输入规格。由于其最小高电平输入电压(VIH)为 2.0 V,因此74HCT240允许从3.3 V至5 V的升压转换。
表2:CMOS逻辑IC的TTL输入规格示例(74VHCT240)
如果前段IC的电源电压低于2V,则不能使用74VHCT240。在这种情况下,需要使用电平转换器(总线开关类型:TC7MPB9326),如图3和表3所示。
表3:电平转换器的供电电压范围示例(TC7MPB9326)
还有一种使用具有开漏输出的产品进行升压转换的方法。由于上拉电阻器Rpull,输出摆动至VCC电平。(图4)
以下文档也包含相关信息。