Low-Power Audio/Video Switches with Audio Volume Control for Dual SCART Connectors

The MAX9670/MAX9671 dual SCART matrices route audio and video signals between a set-top box decoder chip and two external SCART connectors under I²C control. Operating from a 3.3V supply and a 12V supply, the MAX9670/MAX9671 consume 66mW during quiescent operation and 300mW during average operation when driving typical signals into typical loads. Video input detection, video load detection, and a 2.8mW standby mode facilitate the design of intelligent, low-power set-top boxes.

The MAX9670/MAX9671 audio section contains a buffered crosspoint to route audio inputs to audio outputs and programmable volume control from -62dB to 0dB in 2dB steps. The DirectDrive® output amplifiers create a 2VRMS full-scale audio signal biased around ground, eliminating the need for bulky output capacitors and reducing click-and-pop noise. The zero-cross detection circuitry also further reduces clicks and pops by enabling audio sources to switch only during a zero-crossing. The MAX9671 offers TV left and right audio inputs.

The MAX9670/MAX9671 video section contains a buffered crosspoint to route video inputs to video outputs. The standard-definition video signals from the settop box decoder chip are lowpass filtered to remove out-of-band artifacts.

The MAX9670/MAX9671 also support slow-switching and fast-switching signals. An interrupt signal from the MAX9670/MAX9671 informs the microcontroller when the system status has changed.

Applications

* DVD Players * Set-Top Boxes * TVs

* 66mW Quiescent Power Consumption

* 2.8mW Standby Mode Consumption

* Programmable Audio Gain Control of -62dB to 0dB (TV Audio Outputs)

* Clickless, Popless, DirectDrive Audio

* Video Input and Video Load Detection

* Video Reconstruction Filter with 10MHz Passband and 52dB Attenuation at 27MHz

* 3.3V and 12V Supply Voltages