ICS307

Serially Programmable Clock Source

MDS 307 D

3

Revision 042501

Integrated Circuit Systems, Inc. • 525 Race Street • San Jose •CA•95126•(408) 295-9800tel •www.icst.com

Determining the Output Frequency

On power-up the ICS307-01 on-chip registers can have random values, so almost any frequency may be

output from the part. CLK1 will always have some clock signal present, but CLK2 could possibly be OFF

(low).

The ICS307-02 on-chip registers are initially configured to provide a x1 output clock on both the CLK1

and CLK2 outputs. The output frequency will be the same as the input clock or crystal. This is useful if

the ICS307 will provide the initial system clock at power-up. Since this feature is an advantage in most

systems, the ICS307-02 is recommended for new designs.

With programming, the user has full control in changing the desired output frequency to any value over the

range shown in Table 1 on page 4. The output of the ICS307 can be determined by the following simple

equation:

To determine the best combination of VCO, reference, and output dividers, contact ICS application

engineering. You may also fax this page to ICS at 408 295 9818(fax). Be sure to indicate the following:

Your Name ________________ Company Name___________________ Telephone_________________

Respond by e-mail (list your e-mail address) __________________or fax number ___________________

Desired input crystal_______ or clock_______ (in MHz) Desired output frequency_______________

REF Output_______VDD = 3.3V or 5V _______ Duty Cycle: 40-60% _____ or 45-55% required____

CLK1 frequency = Input frequency • 2 •

(VDW+8)

(RDW+2)(OD)

Also, the following operating ranges should be observed:

55 MHz < Input frequency • 2 •

(VDW+8)

(RDW+2)

< 400 MHz

200 kHz <

Input Frequency

(RDW+2)

Where

VCO Divider Word (VDW) = 4 to 511 (0, 1, 2, 3 are not permitted)

Reference Divider Word (RDW) = 1 to 127 (0 is not permitted)

Output Divider = values on page 4

Commercial temperature range.

Industrial temperature limits are

60 MHz to 360 MHz.