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ICS525-01RLFT Datasheet(PDF) 5 Page - Integrated Circuit Systems |
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ICS525-01RLFT Datasheet(HTML) 5 Page - Integrated Circuit Systems |
5 / 9 page User Configurable Clock MDS 525-01/02/11/12 Q 5 Revision 101105 Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com ICS525-01/02/11/12 External Components/Crystal Selection Decoupling Capacitors The ICS525-01/02/11/12 requries two 0.01µF decoupling capacitors to be connected between VDD and GND, one on each side of the chip. The capacitor must be connected close to the device to minimize lead inductance. External Resistors A 33 Ω series termination resistor should be used on the CLK and REF pins. Crystal Load Capacitors The approximate total on-chip capacitance for a crystal is 16 pF, so a parallel resonant, fundamental mode crystal with this value of load (correlation) capacitance should be used. For crystals with a specified load capacitance greater than 16 pF, crystal capacitors may be connected from each of the pins X1 and X2 to Ground as shown in the block diagram. The value (in pF) of these crystal caps should be (CL -16)*2, where CL is the crystal load capacitance in pF. These external capacitors are only required for applications where the exact frequency is critical. For a clock input, connect to X1 and leave X2 unconnected (no capacitors on either). Determining the Output Frequency Users have full control in setting the desired output frequency over the range shown in the tables on pages 3-4. To replace a standard oscillator, users should connect the divider select input pins directly to ground (or VDD, although this is not required because of internal pull-ups) during Printed Circuit Board layout. The ICS525 will automatically produce the correct frequency when all components are soldered. It is also possible to connect the inputs to parallel I/O ports to switch frequencies. By choosing divides carefully, the number of inputs which need to be changed can be minimized. Observe the restrictions on allowed values of VDW and RDW. Configuration Pin Settings The output of the ICS525 can be determined by the following simple equation: Where: Reference Divider Word (RDW) = 0 to 127 (0 not permitted for ICS525-01/-11) VCO Divider Word (VDW) = 0 to 511 (0, 1, 2, 3 not permitted for ICS525-01/-11) Output Divider (OD) = values on pages 3-4 Also, the following operating ranges should be observed: 1. The output frequency must be in the ranges listed on pages 3-4. 2. The phase detector frequency must be above 200 kHz. Since all of the inputs have pull-up resistors, it is only necessary to ground the pins that need to be set to zero. Which Part to Use? The ICS525-01 is the original configurable clock. The ICS525-02 has a higher maximum output grequency and a slightly different set of output dividers. The ICS525-11 has the same divider set as the -01 but is optimized for low frequency operation. The ICS525-12 has the same divider set as the -02 but is optimized for low frequency operation. To determine the best combination of VCO, reference, and output divide, use the ICS525 Calculator on our web site. CLK Frequency Input Frequency 2x VDW 8 + () RDW 2 + () OD • --------------------------------------------- × = 200kHz InputFrequency RDW 2 + () ----------------------------------------------- < |
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