PS2500 datasheet(8/28 Pages) ETC2

8 / 28 page

PS2500 2.2 GHz Fractional-N Frequency Synthesizer

- 8 -

Philsar Semiconductor Inc.

146 Colonnade Road S.

Nepean, Ontario, Canada

K2E 7Y1

Tel: 613-274-0922

Fax: 613-274-0915

www.philsar.com

PMP-001-DS2 V1.2

• The resulting main VCO frequency is 902.453

• Step size is 76.3 Hz

Case 2: Assuming a desired frequency FVCO_main of 917.7786 MHz and a crystal frequency of 19.2 MHz

with operation of the synthesizer in 10-bit mode.

Since the maximum internal reference frequency Fdiv_ref is 25 MHz, the crystal frequency does not require

the internal division to be greater than 1, giving us a Fdiv_ref of 19.2 MHz

1. Therefore, using:

Nfractional = FVCO_main / Fdiv_ref

= 917.7786 x 19.2

= 47.80139

The value to be programmed in the Main Divider Register is:

Nreg = Round [Nfractional] - 32

= Round [47.80139] - 32

= 48 - 32

= 16

= 0 0001 0000 (binary)

With the modulator in 10-bit mode, the value to be programmed in the Main Dividend Registers is:

dividend = Round (divider x (Nfractional - Nreg - 32))

= Round (1024 x (47.80139 - 16 - 32))

= Round (1024 x (-0.19861))

= Round (-203.38133)

= -203 (decimal)

= 11 0011 0101 (binary)

Where 11 0011 0101 is loaded in the Main Dividend MSB Register.

Summarizing,

• Main Divider Register = 0 0001 0000

• Main Dividend MSB Register =11 0011 0101

• The resulting VCO frequency is 917.7938 MHz

• Step size is 18.75 kHz

The frequency step size for this case is 19.2 MHz divided by 2

10 giving 18.75 kHz.

PS2500 датащи(PDF) 8 Page - List of Unclassifed Manufacturers