MK2771-12 Datasheet, PDF (1/4 Pages) Integrated Circuit Systems – VCXO and Set-Top Clock Source

I CR O C LOC K
MK2771-12
VCXO and Set-Top Clock Source
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.
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
AVDD VDD GND
23
2
PCS1:0
UCS
ACS
VIN
13.5 MHz
pullable
crystal
X1
Voltage
Controlled
Crystal
X2 Oscillator
Clock
Synthesis
Circuitry
÷2
Output
Buffer
Output
Buffer
Output
Buffer
Output
Buffer
Output ₂
Buffers
Output
Buffer
Processor Clock
11.0592 MHz
3.6864 MHz
or 18.432 MHz
49.152 MHz
or 24.576 MHz
27.000 MHz
13.500 MHz
MDS 2771-12 A
1
Revision 061699
Printed 11/16/00
MicroClock Division of ICS • 525 Race Street • San Jose • CA • 95126•[phone]tel•[phone]fax