P2027A

http://onsemi.com

2

VCO

PLL

VSS

ModOUT

VDD

Output

Divider

Loop Filter

XIN

XOUT

Crystal

Oscillator

Frequency

Divider

Feedback

Divider

Phase

Detector

Modulation

MRA SR0 SSON

Figure 1. Block Diagram

Table 1. PIN DESCRIPTION

Pin#

Pin Name

Type

Description

1

XIN / CLKIN

I

Crystal connection or external reference frequency input. This pin has dual functions. It can

be connected to either an external crystal or an external reference clock.

2

XOUT

O

Crystal connection. Input connection for an external crystal. If using an external reference,

this pin must be left unconnected.

3

MRA

I

Digital logic input used to select Modulation Rate (see Table 2). This pin has an internal

pull−up resistor.

4

VSS

P

Ground Connection. Connect to system ground.

5

SSON

I

Digital logic input used to enable Spread Spectrum function (Active Low). Spread Spectrum

function enable when low. This pin has an internal pull−low resistor.

6

ModOUT

O

Spread Spectrum Clock Output.

7

SR0

I

Digital logic input used to select Spreading Range (see Table 2). This pin has an internal

pull−up resistor.

8

VDD

P

Connect to +3.3 V Power Supply.

Table 2. MODULATION AND SPREADING SELECTION

MRA

SR0

Spread Range

Modulation Rate

0

0

Reserve

Reserve

0

1

±0.30%

(Fin/10)*34.72 KHz

1

0

±0.20%

(Fin/10)*20.83 KHz

1

1

±0.60%

(Fin/10)*20.83 KHz