3.8.5 VCO Tuning

The Voltage Controlled Oscillator (VCO) tuning process adjusts the digital frequency setting of the VCO before using in the analog PLL loop. See VCO from Related Links. If the VCO is not tuned, the analog control voltage can be outside the operating range of the charge pump and the fractional-N PLL does not lock. For this reason, the ATA8210/15 does not work reliably without VCO tuning.

During operation, a VCO tuning must be executed if the temperature changes by more than 40K or if the VCO frequency changes by more than 25 MHz. This change in VCO frequency corresponds to the following changes in the RF:

  • Low-band (310-318 MHz) – 3 MHz change
  • Low-band (418-477 MHz) – 6 MHz change
  • High-band (836-956 MHz) – 12 MHz change

In general, the recommendation is to activate VCO tuning during every receive service start-up.

As long as no VCO tuning process was performed after power-on, use an initialization value from the EEPROM. Configure the value independently for each service in the eepServices.FEVCT.FEVCT[3:0] variables. The default value is 7.

Address Service0

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x00D0

FEVCT

————

FEVCT[3:0]

A VCO tuning process can be triggered at the following time points:

  • During the start-up of a Receive mode as the operating mode after the system start if enabled in eepTrxConf.sysStartConfig.VCO_TUNE.
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0x0019 sysStartConfig RF_CAL — VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • During the start-up of a Receive mode via the Set System Mode SPI command. See Set System Mode from Related Links.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
systemModeConfig RF_CAL — VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • In PollingMode for each service/channel configuration. See VCO Tuning from Related Links.

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

pollLoopConf[x].config

RfCalib

—

VCOtune

———

EOL

EOP

  • From IDLEMode via the Calibrate and Check SPI command if the EN_VCOCAL bit in tuneCheckConfig is set to ‘1’. See Calibrate and Check from Related Links.
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
tuneCheckConfig —EN_TEMP_MEAS EN_SRCCAL EN_FRCCAL EN_VCOCAL —EN_SELFCHECK —

Setting the VCO_CAL bit within the eepEventConf.cmdRdyConf command ready variable to ‘1’ raises a command ready (CMD_RDY) event on the EVENT pin PB6 after finishing the VCO tuning process.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x0096

cmdRdyConf

—

TEMP_MEAS

SRC_CAL

FRC_CAL

VCO_CAL

RF_CAL

SELFCHECK

—

VCO tuning requires additional time. See Timing Characteristics from Related Links.