4

ICS1522

Power-On Initialization

The ICS1522 has an internal power-on reset circuit that

sets the frequency of the CLK+and CLK- outputs to be half

the crystal or reference frequency assuming that they are

between 10 MHz and 25 MHz (refer to default settings in

Register Definition). Because the power-on reset circuit is

on the VDD supply, and because that supply is filtered,

care must be taken to allow the reset to de-assert before

programming. A safe guideline is to allow 20 microseconds

after the VDD supply reaches four volts.

Board Test Support

It is often desirable to statically control the levels of the

output pins for circuit board test. The ICS1522 supports

this through a register programmable mode, AUXEN. When

this mode is set, AUXCLK will directly control the logic

levels of the CLK+ and CLK- pins while OMUX1, OMUX2,

OMUX3, and OMUX4 will control OUT1, OUT2, OUT3

and OUT4, respectively.

Power Supplies and Decoupling

The ICS1522 has three VSS pins to reduce the effects of

package inductance. Both pins are connected to the same

potential on the die (the ground bus). These pins should

connect to the ground plane of the video board as close to

the package as is possible.

The ICS1522 has a VDDO pin which is the supply of +5

volt power to all output drivers. This pin should be connected

to the power plane (or bus) using standard high-frequency

decoupling practice. That is, capacitors should have low

series inductance and be mounted close to the ICS1522.

The VDD pin is the power supply pin for the PLL synthesizer

circuitry and other lower current digital functions. We

recommend that RC decoupling or zener regulation be

provided for this pin (as shown in the recommended

application circuitry). This will allow the PLL to “track”

through power supply fluctuations without visible effects.

PIN NUMBER

PIN NAME

TYPE

DESCRIPTION

1

IPUMP

OUT

Charge Pump output (External loop filter applications)

2

SDATA

IN/OUT

Serial Data Input/Output

3

SCLK

IN

Serial Clock Input

4

SELn

IN

Serial Port enable (active Low)

5

AVDD

PWR

Analog +5 Volt Supply

6

XTAL1/EXTREF

IN

External Reference Input / Xtal Oscillator Input

7

XTAL2

OUT

Xtal Oscillator Output

8

FINE

IN

Fine Phase Adjust Input

9

VSS

PWR

Ground

10

VSS

PWR

Ground

11

OUT4

OUT

Output 4

12

OUT3

OUT

Output 3

13

VDDO

PWR

Output Driver +5 Volt Supply

14

OUT2

OUT

Output 2

15

OUT1

OUT

Output 1

16

VSS

PWR

Ground

17

IPRG

IN

Output Driver Current Programming Input

18

CLK-

OUT

Differential CLK - Output

19

CLK+

OUT

Differential CLK + Output

20

VDD

PWR

Digital +5 Volt Supply

21

PDEN

IN

Phase Detector Enable (Active High)

22

EXTFBK

IN

External Feedback Input

23

EXTVCO

IN

External VCO input

24

VVCO

IN

VCO Control Voltage Input (External loop filter applications)

Pin Discriptions