MDS 308 F

3

Revision 090704

ICS308

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 acheive 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

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

Setup time

10

ns

Hold time after SCLK

10

ns

Data wait time

10

ns

Strobe pulse width

40

ns

SCLK Frequency

30

MHz

DATA

t

hold

t

setup

SCLK

STROBE

t

s

t

w

Figure 2. Tim ing D iagram for Program m ing the IC S308

Bit160

Bit2

Bit1

Bit3

Bit159

Bit158