Dual Bidirectional Bus Buffer

PCA9601 IC is a high-speed version of P82B96 that is designed to isolate I²C-bus capacitance. It allows greater than 400 pF on SX/SY side and 4000 pF on TX/TY side. It is also a higher version of the PCA9600 that allows many more Fast-mode Plus (Fm+) slaves on remote daughter cards in applications with temperature range of 0°C. It can operate at speeds up to at least 1 MHz, and the high drive side is compatible with the Fast-mode Plus specifications.

The PCA9601 features temperature-stabilized logic voltage level at its SX/SY interface making it suitable for interfacing with buses that have non I²C-bus-compliant logic levels such as SMBus, PMBus, or with microprocessors that use those same TTL logic levels.

The separation of the bidirectional I²C-bus signals into unidirectional TX and RX signals enables the SDA and SCL signal to be transmitted via balanced transmission lines (twisted pairs), or with galvanic isolation using opto or magnetic coupling. The TX and RX signals may be connected together to provide a normal bidirectional signal.

Block Diagram

Block Diagram

Why Used

  • Supply voltage range of 2.5 V to 15 V with I²C-bus logic levels on SX/SY side independent of supply voltage
  • 15 mA SX/SY sink capability yields 5 V Fm+ bus rise time with 470 pF loads
  • 1 MHz operation on up to 20 meters of wire (see AN10658)
  • Splits I²C-bus signal into pairs of forward/reverse TX/RX, TY/RY signals for interface with opto-electrical isolators and similar devices that need unidirectional input and output signal paths
  • Low power supply current

Where Used

  • Simple conversion of I²C-bus SDA or SCL signals to multi-drop differential bus hardware, for example, via compatible PCA82C250
  • Interfaces with opto-couplers to provide opto-isolation between I²C-bus nodes up to 1 MHz
  • Long distance point-to-point or multipoint architectures
  • Interface between I²C-buses operating at different logic levels (for example, 5 V and 3 V or 15 V)
  • Interface between I²C-bus and SMBus (350 μA) standard or Fm+ standard

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