48 MHz Tiny USB Clock Source

MDS 5OSK482 B

2

Revision 111805

Integrated Circuit Systems, Inc.

PRELIM INAR Y INFORM A T ION

ICS5OSK482

Pin Assignment

Pin Descriptions

External Components

External Crystal

The ICS5OSK482 requires a 14.31818 MHz crystal. In

order to minimize ppm errors, the PCB should include

pads for crystal capacitors from pins X1 to ground and

X2 to ground to optimize the initial accuracy. The

capacitor value can be determined by tuning the PCB

so that the error on the reference output is equal to the

initial crystal error.

Crystal Load Capacitors

The device crystal connections should include pads for

small capacitors from X1 to ground and from X2 to

ground. These capacitors are used to adjust the stray

capacitance of the board to match the nominally

required crystal load capacitance. Because load

capacitance can only be increased in this trimming

process, it is important to keep stray capacitance to a

minimum by using very short PCB traces (and no vias)

been the crystal and device. Crystal capacitors must be

connected from each of the pins X1 and X2 to ground.

The value (in pF) of these crystal caps should equal

capacitance in pF. Example: For a crystal with a 8 pF

load capacitance, each crystal capacitor would be 4 pF

[(8-6) x 2 = 4].

X2

GN D

CLK

X1

1

2

3

5

4

VD D

Pin

Number

Pin

Name

Pin

Type

Pin Description

1

X1

Input

25 MHz crystal input. Connect to a parallel resonant fundamental crystal.

2

GND

Power

Connect to ground.

3

CLK

Output

PLL output clock. Internal pull-down resistor.

4

VDD

Power

Connect to 3.3 V.

5

X2

Output

25 MHz crystal output.