ICS1523
Video Clock Synthesizer with I
2
C Programmable Delay
Section 1
Operational Description
Figure 1-1
PLL Functional Blocks
1.1 Naming Conventions
0xY = Register Index Y(hex)
0xY:Z = Register Index Y(hex), bit Z
0xY:Z~Q = Register Index Y(hex), bit Z to Q
1.2 Overview
The ICS1523 is a general purpose, high-performance,
I2C programmable clock generator. It also addresses
stringent graphics system line-locked and genlocked
applications and provides the clock signals required by
high-performance analog-to-digital converters.
Included are a phase-locked loop (PLL) with an over
500MHz voltage controlled oscillator (VCO), a Dynamic
Phase Adjust to provide (DPA) output clocks with a
programmable phase delay with respect to the input
HSYNC. This delay occurs on all PLL outputs including
the differential (PECL) and single-ended (SSTL_3)
high-speed clock outputs and the FUNC output.
The ICS1523 has the ability to operate in line-locked
mode with the HSYNC input or in frequency synthesis
mode with the OSC input with a 7 bit input divider. See
1.4 Voltage Controlled Oscillator (VCO)
The heart of the ICS1523 is a VCO. The VCOs speed
is controlled by the voltage on the loop filter circuit. This
voltage is controlled by the charge pump (CP) and will
be further described later in this section.
1.3 Phase-Locked Loop (PLL)
The phase-locked loop has a very wide input frequency
range (8 kHz to 100 MHz). Not only is the ICS1523 an
excellent, general purpose clock synthesizer, but it is
also capable of line-locked operation.
1.5 Charge Pump (CP) and COAST Input
The CPen bit and COAST input pin can enable and
disable the Charge Pump as needed. See Register
0:7-6. This is for maintaining the correct speed clock
outputs in the absence of reliable HSYNC inputs and is
useful for skipping vertical blanking intervals. These
intervals can have double frequency serration pulses or
even be missing HSYNC pulses completely. The
charge pump is asynchronously disabled and
synchronously re-enabled on the second input HSYNC
after the disable signal goes invalid.
1.6 VCO Divider (VCOD)
The VCOs clock output is first passed through the VCO
Divider (VCOD). The VCOD allows the VCO to operate
at higher speeds than the required output clock. The
VCOD has no effect on the speed of the output clocks,
but it increases the VCO frequency, thereby reducing
jitter and allowing VCO operation between 100 to 500
MDS 1523 Y
Integrated Circuit Systems
2
525 Race Street, San Jose, CA 95126
tel (408) 297-1201
Revision 110905
www.icst.com
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