M64898GP データシートの表示（PDF） - Renesas Electronics

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M64898GP

PLL Frequency Synthesizer with DC/DC Converter For PC

Renesas Electronics 

M64898GP

How to Set The Dividing Ratio of The Programmable Divider

1. Transfer of the 18th bit data (CONT terminal is “L”)

Total divider N is given by the following formulas in addition to the prescaler used in the previous stage.

N = 8 • (32 M + S) M: 9 bit main counter divider

S: 5 bit swallow counter divider

The M and S counters are binary the possible ranges of divider are as follows.

32 • M • 511

0 • S • 31

Therefore, the range of divider N is 8,192 to 131,064.

The tuning frequency fVCO is given in the following equations.

fVCO = fREF • N

= 7.8125 • 8 • (32 M + S)

= 62.5 • (32 M + S) (kHz)

Therefore, the tuning frequency range is 64 MHz to 1023.9375 MHz.

2. Transfer of the 19th bit data (CONT terminal is “L”)

Total divider N is given by the following formulas in addition to the prescaler used in the previous stage.

N = 8 • (32 M + S) M: 10 bit main counter divider

S: 5 bit swallow counter divider

The M and S counters are binary the possible ranges of divider are as follows.

32 • M • 1023

0 • S • 31

Therefore, the range of divider N is 8,192 to 262,136.

The tuning frequency fVCO is given in the following equations.

fVCO = fREF • N

= 3.90625 • 8 • (32 M + S)

= 31.25 • (32 M + S) (kHz)

Therefore, the tuning frequency range is 32 MHz to 1023.96875 MHz.

3. Transfer of the 19th data (CONT terminal is “open”)

Total divider N is given by the following formulas in addition to the prescaler used in the previous stage.

N = 8 • (32M + S) M: 10 bit main counter divider

S: 5 bit swallow counter divider

The M and S counters are binary the possible ranges of divider are as follows.

32 • M • 1023

0 • S • 31

Therefore, the range of divider N is 8,192 to 262,136.

The tuning frequency fVCO is given in the following equations.

fVCO = fREF • N

= 6.25 • 8 • (32 M + S)

= 50.0 • (32 M + S) (kHz)

But, the tuning frequency range is 51.2 MHz to 1300 MHz from the maximum prescaler operating frequency.

Rev.2.00 Jun 14, 2006 page 9 of 13

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