ADRF6821 datasheet(52/61 Pages) AD

52 / 61 page

ADRF6821

Data Sheet

Rev. A | Page 52 of 61

Address: 0x1217, Reset: 0x00, Name: SI_VCO_SEL

Manual VCO Co r e Se le c t

[ 7 : 4 ] RES ERV ED

[ 3 : 0 ] SI_VCO _SEL ( R/W )

Table 63. Bit Descriptions for SI_VCO_SEL

Bits

Bit Name

Settings

Description

Reset

Access

[7:4]

RESERVED

Reserved

0x0

[3:0]

SI_VCO_SEL

Manual VCO Core Select

0x0

R/W

Address: 0x121C, Reset: 0x20, Name: VCO_TIMEOUT_L

Main VCO Calib r atio n Tim e o ut

[ 7 :0 ] V CO _T IM EO UT [ 7 :0 ] ( R/W )

Table 64. Bit Descriptions for VCO_TIMEOUT_L

Bits

Bit Name

Settings

Description

Reset

Access

[7:0]

VCO_TIMEOUT[7:0]

Main VCO Calibration Timeout. This value sets what a timing unit is in the

VCO calibration. It is represented in a number of phase frequency detector

(PFD) periods. For example, 32 is 32 PFD cycles. At a 30.72 MHz PFD rate, this

timer represents an approximately 1 µs period. It is recommended that the user

program this value, depending on their PFD rate, to represent approximately

1 µs to 2 µs. A longer value than necessary leads to longer autocalibration times,

and shorter values may risk autotune accuracy due to insufficient settling times.

0x20

R/W

Address: 0x121D, Reset: 0x00, Name: VCO_TIMEOUT_H

Main VCO Calib r atio n Tim e o ut

[ 7 : 2 ] RES ERV ED

[ 1 :0 ] V CO _T IM EO UT [ 9 :8 ] ( R/W )

Table 65. Bit Descriptions for VCO_TIMEOUT_H

Bits

Bit Name

Settings

Description

Reset

Access

[7:2]

RESERVED

Reserved.

0x0

[1:0]

VCO_TIMEOUT[9:8]

Main VCO Calibration Timeout. This value sets what a timing unit is in the

VCO calibration. It is represented in a number of PFD periods. For example,

32 is 32 PFD cycles. At a 30.72 MHz PFD rate, this timer represents an

approximately 1 µs period. It is recommended that the user program this value,

depending on their PFD rate, to represent approximately 1 µs to 2 µs. A longer

value than necessary leads to longer autocalibration times, and shorter values

may risk autotune accuracy due to insufficient settling times.

0x0

R/W

Address: 0x121E, Reset: 0x14, Name: VCO_BAND_DIV

AFC Meas ur em ent Res olution

[ 7 : 0 ] V CO _BAN D _D IV ( R/W )

Table 66. Bit Descriptions for VCO_BAND_DIV

Bits

Bit Name

Settings

Description

Reset

Access

[7:0]

VCO_BAND_DIV

AFC Measurement Resolution. This value sets how long a single automatic

frequency calibration (AFC) measurement cycle lasts. The AFC measurement

lasts 16 × VCO_BAND_DIV. It is required that the user program this value,

depending on their PFD rate, to represent approximately 10 µs. A longer value

than necessary leads to longer autocalibration times, and shorter values may

risk autotune accuracy due to insufficient frequency measurement resolution.

0x14

R/W

Address: 0x121F, Reset: 0x00, Name: VCO_FSM

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