CC1020-RTR1 datasheet(46/95 Pages) TI1

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ref

min

80.75

220

[ ]

ref

839

6 pF

[ ]

ref

21823

[ ]

ref

80.75

[ ]

ref

7126

[ ]

ref

3037

7 pF

VCO

ref

FREQ

0.5

DITHER

8192

CC1020

SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015

www.ti.com

The VCO frequency is given by Equation 24.

(24)

The VCO frequency is divided by 2 and by 4 to generate frequencies in the two bands, respectively.

The VCO sensitivity (sometimes referred to as VCO gain) varies over frequency and operating conditions.

Typically the VCO sensitivity varies between 12 and 36 MHz/V. For calculations the geometrical mean at

21 MHz/V can be used. The PLL calibration (explained below) measures the actual VCO sensitivity and

adjusts the charge pump current accordingly to achieve correct PLL loop gain and bandwidth (higher

charge pump current when VCO sensitivity is lower).

Equation 25 through Equation 29 can be used for calculating PLL loop filter component values, see

Figure 6-1, for a desired PLL loop bandwidth, BW.

(25)

(26)

(27)

(28)

(29)

Define a minimum PLL loop bandwidth as shown in Equation 30.

(30)

If BWmin > Baud rate/3 then set BW = BWmin and if BWmin < Baud rate/3 then set BW = Baud rate/3 in

Equation 25 through Equation 29.

There are two special cases when using the recommended 14.7456 MHz crystal:

1. If the data rate is 4.8 kBaud or below and the channel spacing is 12.5 kHz the following loop filter

components are recommended:

C6 = 220 nF

C7 = 8200 pF

C8 = 2200 pF

R2 = 1.5 k

R3 = 4.7 k

2. If the data rate is 4.8 kBaud or below and the channel spacing is different from 12.5 kHz the following

loop filter components are recommended:

C6 = 100 nF

C7 = 3900 pF

C8 = 1000 pF

R2 = 2.2 k

R3 = 6.8 k

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