ICS308
SERIAL PROGRAMMABLE QUAD PLL VERSACLOCK SYNTHESIZER SER PROG CLOCK SYNTHESIZER
IDT™ / ICS™
SERIAL PROGRAMMABLE QUAD PLL VERSACLOCK SYNTHESIZER 3
ICS308 REV L 051310
Configuring the ICS308
Initial State: The ICS308 may be configured to have up to nine frequency outputs, utilizing the four
on-board PLLs. Unprogrammed, the part has the following outputs, related to the reference input clock:
The STROBE pin must have an external 250 kOhm pull-up resistor to achieve the Initial State.
The input crystal range for the ICS308 is 5 MHz to 27 MHz.
The ICS308 can be programmed to set the output functions and frequencies. 160 data bits generated by
the VersaClock
TM
software are written in DATA pin in this order: MSB (left most bit) first.
As show in Figure 2, after these 160 bits are clocked into the ICS308, taking STROBE high will send this
data to the internal hatch and the CLK output will lock within 10 ms.
Note: STROBE utilizes a transparent latch that is latched when in the high state. If STROBE is in the high
state and SCLK is pulsed, DATA is clocked directly to the internal latch and the output conditions will
change accordingly. Although this will not damage the ICS308, it is recommended that STROBE be kept
low while DATA is being clocked into the ICS308 in order to avoid unintended changes on the output clocks.
All outputs may be turned off during initialization by bringing the PDTS
pin to Ground. When PDTS is
brought high, after the Strobe pin in brought high, the programmed output frequencies will be available.
AC Parameters for Writing to the ICS308
Default Outputs
Output Frequency
Clock 1-9 (Pins 4, 10 - 14) Reference Output
Parameter Condition Min. Max. Units
t
SETUP
Setup time 10 ns
t
HOLD
Hold time after SCLK 10 ns
t
W
Data wait time 10 ns
t
S
Strobe pulse width 40 ns
SCLK Frequency 30 MHz
DATA
t
hold
t
setup
SCLK
STROBE
t
s
t
w
Figure 2. Timing Diagram for Programming the ICS308
Bit160 Bit2 Bit1
Bit3
Bit159 Bit158