The need of voltage level translators?


The need for voltage level translation is becoming increasingly significant in today's electronic systems. As the digital switching level standards have continued to progress toward lower voltage levels, system incompatibilities have arisen. Figure 1 illustrates the trend toward lower system voltage levels and demonstrates the incompatibilities that mixed voltage systems can face.

Voltage Levels for Translators

 

For two devices to interface reliably, the output driver voltages must be compatible with receiver input thresholds. For this condition to be met in mixed voltage systems, a voltage translator is often required. These translators can help remedy many problems in system voltage compatibility but do require DIR (direction) control pins. If the system environment does not provide a programmable GPIO to control the direction pin, an auto-direction sensing translator architecture can provide an alternative translation solution.

Translation devices can be found in almost every market, including: consumer electronics, portable electronics, computing, automotive, industrial and networking applications. Wherever the need exists to interface lower operating processors with higher operating peripherals.

 

voltage levels

Direction Controlled Translators:

Direction Controlled translators performs non-inverting up or down translation of a uni-directional signal. These translators have one or more direction control pins that allow the designer to configure which pins are inputs and outputs. This enables simultaneous up and down translation on one device and gives the user more flexibility. Many devices within this class are available with Bus Hold, which allows the device to retain the last known state of the output when the inputs are floating or become high impedance. Bus Hold feature is indicated by “H” in the part number.

Benefits of Direction Controlled:

  • Buffered output for high drive strength
  • One or more direction control pins
  • Devices available that have been optimized for common interfaces
  • Bus Hold functionality available

Auto Bi-Directional Translators:

Auto Bi-Directional translators are a class of voltage translators, which are available in dual supply configurations. Yet unlike the direction controlled translators they automatically sense the direction of the signal without the need for a direction control pin. Across the three families within the class there are a number of trade-offs including drive-strength, data rate, and multivoltage translation. The wide range of available functionalities gives the designer a number of parts to choose from TI’s portfolio to suit their needs.

Benefits of Auto Bi-Directional:

  • Works with bi-directional signals
  • Devices available that have been optimized for common interfaces
  • Works with both open-drain and push-pull interfaces
  • Design flexibility with external pull-up resistors

Uni-Directional Translators:

This class of translators performs a single direction, noninverting up or down translation of an incoming signal at the input of a device to the output of the device. Single supply translators only have one supply voltage, which provides the reference level for the output to track. Single supply translators include translating buffers, as well as translating logic gates. Translating logic gates have built-in logic functionality, and at the same time perform up or down voltage translation. Dual supply translators have two supply voltages, one at the VCC level of the input signal, the other at the VCC level of the output signal.

Benefits of Uni-Directional: 

  • Single supply translators provide simplicity in system design
  • Dual supply translators provide dynamic operating range for voltage translation
  • Voltage translating logic gates achieve two functions in one chip