In modern electronic systems, different modules or devices often operate at different voltage levels. For example, a processor might operate at 1.8V, while a connected sensor operates at 5V. This voltage discrepancy can lead to signal distortion, equipment damage, or communication failure. To address these issues, voltage-level translators, also known as level shifters, have been developed.

Overview of Voltage-Level Translators

A voltage-level translator/level shifter, is an electronic device designed to convert signals from one voltage domain to another, ensuring that devices operating at different voltages can interact correctly. It typically consists of an input stage, an output stage, and an intermediate conversion circuit. The intermediate conversion circuit adjusts the input signal's characteristics to match the required output signal level based on the input signal's features and requirements.

The working principle of a voltage-level translator is based on voltage comparison, driving, and logic conversion technologies. During operation, the translator first compares the input signal's voltage to determine if it meets the conversion criteria. If the input signal's level is below or above the target level, the translator triggers the corresponding conversion operation.

● Unidirectional Level Translation: Suitable for unidirectional communication protocols such as SPI and UART. Implementation methods include resistor voltage division and transistor/diode circuits. Resistor voltage division uses a resistor network to step down the voltage, offering extremely low cost but only supporting low-speed signals. Transistor/diode circuits work by cutting off when the input is high and conducting when the input is low, thereby converting the signal's high and low levels.

● Bidirectional Level Translation: The core component is an N-channel MOSFET paired with a pull-up resistor. When converting from the high-voltage side to the low-voltage side, the MOSFET conducts or cuts off to achieve the low-voltage side's high and low levels. When converting from the low-voltage side to the high-voltage side, when the low-voltage output is low, the MOSFET's body diode conducts, pulling the high-voltage side low.

Key features of voltage-level translators include voltage range, propagation delay, drive capability, and signal protection. The voltage range specifies the input (Vin) and output (Vout) voltage domains, ensuring the translator can accommodate different voltage requirements. Propagation delay refers to the time delay of the signal through the circuit, which is crucial for high-speed interfaces such as SPI. Drive capability indicates the load the output can drive, ensuring stable signal transmission. Signal protection functions safeguard the input and output ports from abnormal conditions such as overvoltage, overcurrent, and short circuits.

Voltage-level translators are widely used in electronic systems that require communication across voltage domains. Typical scenarios include:

● Embedded Systems and Microcontrollers(MCUs): Such as a 3.3V microcontroller driving a 5V sensor, or a 1.8V FPGA connected to a 3.3V peripheral.

● Automotive Electronics: For example, communication between low-voltage processors and 12V actuators in in-vehicle infotainment systems and advanced driver-assistance systems (ADAS).

● Communication Equipment: Data exchange between a 1.5V processor and a 3.3V Ethernet PHY chip in routers.

Types of Voltage Level Translators

Voltage level translators can be categorized based on conversion direction, speed and protocol, and power supply method.

1. By Conversion Direction:

● Unidirectional Conversion ICs: These support signal conversion from one voltage domain to another (e.g., 5V→3.3V). They have a simple structure and are cost-effective.

● Bidirectional Conversion ICs: These can achieve bidirectional transmission without a control signal and are suitable for bidirectional buses such as GPIO and I²C.

2. By Speed and Protocol:

● General Low-Speed ICs: These support signals up to 100Mbps (such as GPIO, UART) and offer good cost-performance ratios.

● High-Speed ICs: These are suitable for high-speed signals such as USB and HDMI (with rates up to several Gbps) and require addressing signal integrity issues.

● Protocol-Specific ICs: These are optimized for specific protocols such as I²C, CAN, and RS485.

3. By Power Supply:

● Single-Power-Supply ICs: These require only one power supply (usually the high-voltage domain) and are suitable for simple unidirectional conversion.

● Dual-Power-Supply ICs: These connect to power supplies from both voltage domains and are the mainstream choice for bidirectional conversion due to their strong compatibility.

Popular level shifter IC Models and Selection Suggestions

In the market for voltage-level translators, several popular models are available.

When selecting a voltage-level translator, it is essential to consider factors such as voltage range, propagation delay, and drive capability to ensure optimal performance in different application scenarios. Choose the appropriate model based on the application. For example, if high-speed transmission is required, opt for a high-speed chip. For low-power applications, consider a low-power model. Additionally, ensure that the selected model's voltage range and protocol match the actual application.

Conclusion

Voltage-level translators are indispensable components in modern electronic systems. They precisely convert voltage levels to solve signal compatibility issues between different voltage domains. Whether for unidirectional or bidirectional communication, analog or digital signals, there is a suitable level translator available. Choosing the right level translator can ensure stable signal transmission across different voltage domains, enhancing the system's reliability and performance.

Website: www.conevoelec.com

Email: info@conevoelec.com