How to Use SN74LVC1T45: Examples, Pinouts, and Specs

The SN74LVC1T45 is a single-bit, dual-supply level shifter manufactured by Texas Instruments. It is designed to enable bidirectional voltage translation between two different voltage levels, making it an essential component for interfacing devices operating at different logic levels. This component is highly versatile and supports a wide range of voltage levels, making it suitable for modern low-power and mixed-voltage systems.

• Interfacing between 1.8V, 3.3V, and 5V logic devices.
• Communication between microcontrollers and peripherals with differing voltage levels.
• Voltage level translation in I²C, SPI, or UART communication protocols.
• Mixed-voltage systems in consumer electronics, industrial automation, and IoT devices.

• Operating Voltage Range:
  • V_CCA: 1.65V to 5.5V
  • V_CCB: 1.65V to 5.5V
• Data Rate:
  • Up to 380 Mbps (push-pull configuration)
  • Up to 24 Mbps (open-drain configuration)
• Input/Output Type: CMOS
• Operating Temperature Range: -40°C to 125°C
• Drive Strength: ±24 mA at 3.3V
• Package Options: SOT-23, SC-70, and others.

The SN74LVC1T45 is available in a 6-pin SOT-23 or SC-70 package. Below is the pinout and description:

1. Power Supply Connections:

   • Connect V_CCA to the supply voltage of the device on side A.
   • Connect V_CCB to the supply voltage of the device on side B.
   • Ensure that both supply voltages are within the specified range (1.65V to 5.5V).

2. Direction Control:

   • Use the DIR pin to control the direction of data flow:
     • Set DIR = High for A → B translation.
     • Set DIR = Low for B → A translation.

3. Data Connections:

   • Connect the A pin to the signal line of the device operating at V_CCA.
   • Connect the B pin to the signal line of the device operating at V_CCB.

4. Bypass Capacitors:

   • Place decoupling capacitors (e.g., 0.1 µF) close to the V_CCA and V_CCB pins to ensure stable operation.

• Ensure that the DIR pin is not left floating; it must always be driven high or low.
• Avoid exceeding the maximum voltage ratings for V_CCA, V_CCB, or any I/O pins.
• For high-speed applications, minimize trace lengths to reduce signal degradation.
• Use pull-up resistors if the component is used in open-drain configurations.

The following example demonstrates how to use the SN74LVC1T45 to interface a 3.3V sensor with a 5V Arduino UNO.

• Connect V_CCA to 3.3V (sensor side).
• Connect V_CCB to 5V (Arduino side).
• Connect GND to the common ground of the system.
• Connect the sensor's data line to the A pin.
• Connect the Arduino's data line to the B pin.
• Set DIR = High for sensor → Arduino communication.

// Example: Reading data from a 3.3V sensor using SN74LVC1T45 level shifter
// Ensure DIR pin is set HIGH for A to B translation (sensor to Arduino).

const int sensorPin = 2; // Pin connected to the sensor (A side of SN74LVC1T45)
const int dirPin = 3;    // Pin connected to DIR control of SN74LVC1T45

void setup() {
  pinMode(sensorPin, INPUT); // Set sensor pin as input
  pinMode(dirPin, OUTPUT);   // Set DIR pin as output
  digitalWrite(dirPin, HIGH); // Set DIR HIGH for A to B translation

  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int sensorValue = digitalRead(sensorPin); // Read sensor value
  Serial.println(sensorValue); // Print sensor value to Serial Monitor
  delay(100); // Small delay for readability
}

1. Can the SN74LVC1T45 handle bidirectional communication automatically?

   • No, the direction must be manually controlled using the DIR pin.

2. What is the maximum voltage difference between V_CCA and V_CCB?

   • There is no strict limit on the voltage difference as long as both are within the 1.65V to 5.5V range.

3. Can I use the SN74LVC1T45 for analog signals?

   • No, this component is designed for digital signals only.

4. Is it necessary to use pull-up resistors?

   • Pull-up resistors are only required in open-drain configurations.

This concludes the documentation for the SN74LVC1T45. For further details, refer to the official Texas Instruments datasheet.