Integrated
Circuit
Systems, Inc.
ICS1572
User Programmable Differential Output Graphics Clock Generator
Description
The
ICS1572
is a high performance monolithic phase-locked
loop (PLL) frequency synthesizer. Utilizing ICS’s advanced
CMOS mixed-mode technology, the
ICS1572
provides a low
cost solution for high-end video clock generation in worksta-
tions and high-end PC applications.
The
ICS1572
has differential video clock outputs (CLK+ and
CLK-) that are compatible with industry standard video DACs.
Another clock output, LOAD, is provided whose frequency is
derived from the main clock by a programmable divider. An
additional clock output is available, LD/N2, which is derived
from the LOAD frequency and whose modulus may also be
programmed.
Operating frequencies are fully programmable with direct con-
trol provided for reference divider, pre-scaler, feedback divider
and post-scaler.
Reset of the pipeline delay on Brooktree RAMDACs may
be performed under register control. Outputs may also be set
to desired states to facilitate circuit board testing.
Features
•
•
•
•
•
•
Supports high-resolution graphics - CLK output to
180 MHz
Eliminates need for multiple ECL output crystal oscillators
Fully programmable synthesizer capability - not just a
clock multiplier
Available in 20-pin 300-mil wide body SOIC package
Available in both parallel (101) and serial (301)
programming versions
Circuit included for reset of Brooktree RAMDAC pipeline
delay
Applications
•
•
•
Workstations
AutoCad Accelerators
High-end PC graphics systems
ICS1572-101 Pinout
N.C.
AD0
XTAL1
XTAL2
STROBE
VSS
VSS
LOAD
LD/N2
N.C.
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
N.C.
AD1
AD2
VDD
VDD
VDDO
IPRG
CLK+
CLK-
N.C.
LOOP
FILTER
XTAL1
XTAL2
CRYSTAL
OSCILLATOR
/R
PHASE-
FREQUENCY
DETECTOR
CHARGE
PUMP
VCO
BLANK
�½
EXTFBK
(-301 only)
MUX
/M
/A
PRESCALER
PROGRAMMING
INTERFACE
MUX
/2
/4
/ N1
FEEDBACK DIVIDER
ICS1572-301 Pinout
DIFF.
OUTPUT
CLK+
CLK
−
MUX
DRIVER
LOAD
/ N2
DRIVER
LD/N2
N.C.
AD0
XTAL1
XTAL2
STROBE
VSS
VSS
LOAD
LD/N2
N.C.
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
N.C.
AD1
AD2
VDD
VDD
VDDO
IPRG
CLK+
CLK-
N.C.
Figure 1
ICS1572RevC093094
RAMDAC is a trademark of Brooktree Corporation.
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
