STW81101 datasheet(27/42 Pages) STMICROELECTRONICS

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STW81101

I2C bus interface

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and P is the selected Prescaler Modulus

5.3.6

CALIBRATION

This register controls VCO calibrator.

INITCAL: resets the auto-calibrator State Machine (writing to "1" and back to "0")

SERCAL: at "1" starts the VCO auto-calibration (should be reset to "0" at the end of

calibration)

SELEXTCAL: test purpose only; must be set to '0'

CAL[4:0]: test purpose only; must be set to '0'

5.3.7

READ-ONLY register

This register is automatically addressed in the 'current byte address read mode'.

DEV_ID[1:0]: device identifier bits; returns '00'

LOCK_DET: "1" when PLL is locked

INTCAL[4:0]: internal value of the VCO control word

5.4

VCO calibration procedure

The calibration of the VCO center frequency is activated by a '0' to '1' transition of the

SERCAL bit (CALIBRATION Register bit[6]).

In order to program properly the device, ensuring the VCO calibration, the following

procedure is required before every channel change:

Program all the Registers using a multi-byte write sequence with the desired

settings (Functional Mode, B and A counters, R counter, VCO amplitude, Charge

for Direct Output

where DR equals

0.5

for Output Divided by 2

0.25

for Output Divided by 4

MSB

LSB

INIT

CAL

SER

CAL

SEL

EXT

CAL

CAL4

CAL3

CAL2

CAL1

CAL0

MSB

LSB

DEV_ID1

DEV_ID0

LOCK_

DET

INT

CAL4

INT

CAL3

INT

CAL2

INT

CAL1

INT

CAL0

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