MC44BS373CADR2 datasheet(27/52 Pages) FREESCALE

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MC44BS373CA Data Sheet

High Speed I2C Compatible Bus

Figure 10. PLL Loop Filter

Loop filter equation:

•

ωo = 3-dB cutoff frequency

•

Kpd = 1-

µA phase detector current

•

Kosc = 5 MHz/V sound oscillator slope. (In fact, Kosc = 40 MHz/prescaler divider = 8.) This

provides 5 MHz/V.

•

N = Sound divider ratio

•

Q = quality factorvR

C2, added to minimize glitches, is usually set to one tenth the size of C1. For example:

•

Fref = 31.25 kHz

→ N = 5.5 MHz / 31.25 kHz = 176

Assuming C1 = 1

µF, then

ωo = 168 rad, and Fo = 27 Hz

Q depends on the desired frequency response. Choosing Q = 0.7 as a starting point, then R = 8.5 K

Ω. The

resistance acts directly on the factor quality and can be adjusted to create a peak on the low-frequency range.

It is recommended that the value of R be adjusted experimentally depending on the application and

requirements.

16 High Speed I2C Compatible Bus

16.1 Specification Conditions

Each of the characteristics listed in Table 27 and Table 28 is classified as one of the following types:

•

A—100% tested

•

B—100% correlation tested

•

C—Characterized on samples

•

D—Design parameter

See Section 14, “Characterization Measurement Conditions,” for each C-type parameter.

Unless otherwise specified, VCC = 5.0 V, TA = 25°C.

ωo

Kpd

Kosc

NC1

------------------------------

RC1

ωo

-------------------------------

with

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