I2C-isolator ISO1640 - Qwiic

Pololu I²C Isolator with Connectors, ISO1640 – Safe Galvanic Isolation for I²C Buses. The Pololu ISO1640 module provides galvanic (electrical) isolation between two I²C domains while maintaining full bidirectional communication, including clock stretching on both SCL and SDA lines. The module uses Texas Instruments’ ISO1640B chip, supporting data rates up to 1.7 MHz. It is equipped with two JST SH 4-pin connectors compatible with the Qwiic standard.

Specifications:

• Rated voltage, side 1 (VCC1): 3.0 V – 5.5 V
• Rated voltage, side 2 (VCC2): 2.25 V – 5.5 V
• Data rate: up to 1.7 MHz
• Built-in pull-up resistors: 10 kΩ on both sides (external pull-ups can be added)
• Isolation (chip): up to 3 kV RMS (PCB clearance limited to 2 mm)
• Connector type: JST SH 4-pin (compatible with Qwiic / STEMMA QT)

Function and use:

Galvanic isolation ensures that there is no direct electrical connection between GND1 and GND2. Both SDA and SCL lines are fully bidirectional, allowing devices on either side to operate as master or slave. Each side must have its own power supply — GND1 and GND2 must not be connected.

The built-in 10 kohm pull-up resistors may be sufficient for lower data rates, but external pull-ups may be required for high-speed I²C operation. The PCB clearance is approximately 2 mm, which should be considered in applications requiring higher isolation levels.

On side 1, the outputs do not pull fully to 0 V but typically remain around 0.5–0.7 V when side 2 drives low. The logic on side 1 must tolerate this voltage level.

Advantages and application examples:

• Protects against ground loops, voltage differences, and electrical noise between two I²C devices.
• Suitable for systems with separate voltage domains or where isolation is required for safety or noise reduction.
• Compact design with pre-fitted connectors allows easy integration into Qwiic or STEMMA QT based systems.
• The galvanic isolation prevents faults or transients from propagating directly across the I²C bus.