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Bidirectional bus buffer meets HDMI requirements

Posted: 07 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:HDMI? bidirectional bus buffer? capacitance?

Linear Technology has introduced the LTC4307-1, an HDMI-compliant bidirectional bus buffer that provides capacitance buffering and level shifting between HDMI source and sink devices. The HDMI standard requires that devices have less than 50pF of input capacitance on their display data channel (DDC), a 2-wire bus that passes digital data from the sink device (such as a DTV) to the high-definition video source device. LTC4307-1 offers sub-10pF data and clock input capacitance along with a capacitance buffering feature, allowing devices to pass the HDMI DDC input capacitance compliance test with ease.

The LTC4307-1 bidirectional capacitance buffering isolates the internal bus capacitance that may be larger than 50pF, while presenting sub-10pF to the HDMI cable. Level translation is incorporated into the part to allow 3.3V HDMI devices to interface safely to the 5V HDMI DDC bus. The LTC4307-1 provides undervoltage lockout protection, and further avoids corruption of data by monitoring both its input and output bus for completion of data transactions before connecting to the bus. A READY output pin provides a digital flag to indicate the busses are connected and ready to communicate, and can be used to control the HDMI Hot Plug Detect (HPD) signal. The LTC4307-1 adds only 60mV of logic low offset, allowing several to be cascaded in series without exceeding VOL limits.

The LTC4307-1 is offered in small 8-pin 3mm x 3mm DFN or 8-lead MSOP packages, with 5kV Human Body Model ESD protection. Pricing begins at $2.15 in 1,000 piece quantities.

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