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I²C Hot-swappable bus and SMBus buffer

NCA9511 is a hot-swappable I²C bus buffer that supports insertion of I/O cards into a powered backplane without damaging the data or the clock bus. The control circuit prevents the backplane side I²C line (input) from connecting to the card side I²C line (output) until a stop command or bus idle condition occurs on the backplane and there is no bus contention on the card. After the connection is established, the component will provide two-way buffering so that the capacitors of the backplane and card remain separate. During insertion, the SDA and SCL wires are pre-charged to 1V to minimize the current required to charge the parasitic capacitance of the component. When the I²C bus is idle, the NCA9511 can be set to shutdown mode by setting the EN pin low, thereby reducing power consumption. When EN is pulled high, NCA9511 resumes normal operation. It also includes an open-drain READY output pin that indicates that the backplane is connected to the card side. When READY level is high, SDAIN and SCLIN are connected to SDAOUT and SCLOUT. When both sides are disconnected, READY level is low.

Product Features

• Supporting  bidirectional data transmission signal of PC bus

• Operation power supply voltage range is 2.7V to 5.5V

• The TA ambient temperature range is from -40°C to 105°C

• 1-V precharging on all SDA and SCL lines prevents damage during field insertion

• Compatible with standard mode and fast mode I²C components

• Supporting clock stretching, arbitration and synchronization

• I²C BUS high-impedance state when VCC is powered down

• Operation temperature: -40℃~105℃

• RoHS compliant package: MSOP8, SOP8


• Telecom switching equipment

• Server

• Enterprise switch

• Base station

• Industrial automation equipment

Functional Block Diagram


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