MK2771-12

I C R O C LOC K Description The MK2771-12 is a low cost, low jitter, high performance VCXO and clock synthesizer designed for set-top boxes. The on-chip Voltage Controlled Crystal Oscillator accepts a 0 to 3V input voltage to cause the output clocks to vary by ±100 ppm. Using MicroClock’s patented VCXO and analog Phase-Locked Loop (PLL) techniques, the device uses an inexpensive 13.5 MHz crystal input to produce multiple output clocks including a selectable processor clock, selectable UART and audio clocks, a fixed 11.0592 MHz, and two low skew copies of the 27 MHz. All clocks are frequency locked to the 27.00 MHz output (and to each other) with zero ppm error, so any output can be used as the VCXO output. This chip directly replaces the MK2771-02 when a 13.5 MHz input crystal is substituted for the 14.31818 MHz used on the -02. Additionally, the -12 adds 24.576 MHz to the ACLK. MK2771-12 VCXO and Set-Top Clock Source Features Packaged in 20 pin SOIC Pin for pin and functional upgrade to MK2771-02 Uses an inexpensive 13.5 MHz crystal On-chip patented VCXO with pull range of 200 ppm VCXO tuning voltage of 0 to 3 V Processor frequency of 16.67 MHz, 20 MHz, 32 MHz, 40 MHz, or 50 MHz Zero ppm synthesis error in all clocks (all exactly track 27MHz VCXO) - patented 25 mA output drive capability at TTL levels Advanced, low power, sub-micron CMOS process 5 V operating voltage Block Diagram 2 AVDD VDD GND 2 3 Output Buffer Output Buffer Clock Synthesis Circuitr...