Translators, Level Shifters
1. What are Logic Translators and Level Shifters?
1) Core Function
It is used to solve the signal compatibility problem between devices with different logic levels or voltage domains, and ensure the accuracy of cross-voltage domain communication by converting the voltage or logic level of the input signal.
2) Main Functions
Signal Compatibility: adapt to devices with different voltage standards (such as TTL and CMOS);
Voltage Adaptation: prevent high voltage from damaging low-voltage devices (such as gate breakdown) or low-voltage signals from driving high-voltage circuits;
Logic Conversion: realize logic level matching in bidirectional signal transmission.
2. How do Logic Translators and Level Shifters Work?
1) Voltage Adjustment: dynamically adjust the logic threshold of the input signal through resistor voltage division, transistor switch, or dedicated conversion circuit (such as input higher than the threshold voltage output high level, vice versa output low level).
2) Dedicated Converter Structure:
Low→High Voltage Conversion: Use NMOS driver or charge pump to increase voltage swing;
High→Low Voltage Conversion: Limit voltage range through PMOS voltage divider or current limiting resistor;
Bidirectional Conversion: Typically used in buses such as I²C, using cross-coupled positive feedback circuits to achieve bidirectional level compatibility.
3. What are Logic Translators and Level Shifters Used for?
Digital Circuit Interconnection: Multi-voltage domain chip design (such as CPU core low voltage domain and peripheral high voltage domain communication);
Communication Interface: Signal level adaptation of protocols such as UART, I²C, and single bus;
Power Management: Signal interaction between the power gating domain (shutdown module) and normal domain;
Sensor Interface: Connect sensors with different operating voltages to the main control chip.
4. Key Design Parameters for Logic Translators and Level Shifters
Type Selection: including unidirectional/bidirectional converters, number of pins (such as SOT-23, VSSOP packages), supported voltage range (such as 0.8V↔3.3V) and conversion rate;
Selection Parameters: logic threshold voltage, drive current, transmission delay, and withstand voltage value;
Failure Protection: integrated overvoltage/overcurrent protection mechanism to prevent device damage caused by abnormal levels.
5. Technology Evolution of Logic Translators and Level Shifters
From the early simple voltage divider resistor solution, it has developed into an integrated design based on MOS transistor level (such as cross-coupling structure) to improve conversion accuracy and response speed;
Modern level converters support nanosecond delays and are suitable for high-speed communication scenarios (such as DDR memory interface).