Top Questions About Auto Bi-Direction LSF Family Translators
Abstract
The LSF Type translators utilize passive switches to level shift voltages, allowing the device to support both open drain and push pull interface signals. Board designers have the freedom to adjust the device behavior with external components to satisfy specific system needs. As a result, designing with the LSF Family requires additional attention due to specific biasing requirements, external RC component guidelines, and other design considerations.
This application note takes a deeper look into some of the most commonly asked questions regarding this device and serves as an extension to the existing app note regarding the operation of the LSF family devices. Please see Voltage Translation with the LSF Family for an introduction to how the LSF Family devices operate in example applications.
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1 How Does the LSF000x Differentiate From the LSF010x During Setup?
Both variants of the LSF devices share similar architecture, but the LSF000x design requirements are less stringent than the LSF010x. The LSF000x only uses one power supply to directly bias the gates of the channel FETs to perform translation, removing the requirement to operate with two power supplies. Since LSF000x can operate with a single power supply, the device eliminates the need for VREFB to be shorted to EN, as well as the external 200kΩ bias resistor. The key consideration with the LSF000x is that VBIAS must be referenced to the lower voltage of VEXT,A and VEXT,B. Figure 1-1 depicts setup differences:
Figure 1-1 LSF000x Setup
Figure 1-2 LSF010x Setup