Logic Level Translators

Logic level translators adapt or convert one voltage or logic level to another. They are used in devices that operate at multiple voltage levels. Devices that often use logic level translators include microprocessors and integrated circuits that have inputs and outputs functioning at 1.8 volts and logic levels for flash memory or panel display requiring 3.3 volts. These mismatched voltages can be mitigated between the integrated circuit (IC) and the device by using the logic level translator.

Logic level translators are frequently used in portable devices, such as cell phones, personal digital assistants, digital cameras, and many other battery-operated devices. Dual-supply translators are capable of translating logic levels up or down within a specific range. Dual-supply voltage level translators are used with complementary metal-oxide semiconductor (CMOS) circuits to translate between 3 volt logic and 5 volt logic signals. These logic level translators are specially designed to handle a voltage input high (VIH) signal in both directions. A voltage level translator may be one of two different configurations: a dual supply translator or a configurable voltage interface transceiver. A configurable transceiver is useful in an application where a CMOS input is left floating; for example, when a card or cable is left disconnected.

Logic level translators may also use a pull-up resistor to translate between logic levels. A pull-up resistor is used in a logic level translator to translate transistor-transistor logic (TTL) to CMOS logic. Logic level translators are also used to translate voltages between low supply voltages in mixed signal integrated circuits and other digital components. Logic level translation methods vary from application to application, and are dependent upon the range of voltage between the IC chip and the device; the number of lines being translated, for example, a 4-line serial interface will require different translation techniques than a 32-bit data bus; and the speed of signals.

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