RF2968 Просмотр технического описания (PDF) - RF Micro Devices

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RF2968

BLUETOOTH™ TRANSCEIVER

RF Micro Devices 

RF2968

Preliminary

Special Modes of Operation

Calibration

When the RF2968 is Reset (CLRB=0), all calibration values are cleared. Therefore, after the RF2968 is powered up

from the OFF state, it must be instructed to perform its self-calibration. Circuits requiring calibration include the RX vari-

able gain amplifier (VGA), TX and RX PLL’s, RX channel filter, RX data paths, and TX Gaussian filter.

Calibration instructions are sent from the baseband to the RF2968 via the serial port (addressing Registers 5 and 7) and

must be performed in the order shown in the table below. After a calibration instruction is sent, the baseband must delay

for the length of time indicated before sending the next calibration instruction; this allows time for the RF2968 circuits to

settle and execute the instruction. At initialization, BypassSM, PU_XTAL, PU_MULT, and TX_EN are set high and

remain so for the duration of the calibration. Register 7 is only addressed during initialization to set TX_EN and configure

the reference frequency and RF PLL frequency.

11

.

Calibration Steps

Initialization of PLL

Initialization of

Chip Control

Calibrate KO of TX and

RX IF PLL’s

Calibrate Gaussian TX

and RX VGA

Calibrate IF Filters

Calibrate RX Offsets

Return Chip Control to

State Machine

Bit Settings for Calibration Sequencea

Register 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

7

0 0 0 0 xb xb xb 1 0 xc xc xc xc xc xc xc

5

1000000011000000

Required Time (usec)

0d

2500

5

1000010011000000

1024

5

1000101011000101

5

1000000011100101

5

1000000011010100

5

0000000000000000

Total Calibration Time:

285

608

64

0

4481

Notes:

a) Shaded cells indicate no change from previous state.

b) Set according to reference frequency.

c) Set RF PLL frequency to a valid frequency (LO=2403 to 2481MHz).

d) Register 5 may be programmed immediately after Register 7.

Transmitter Test Mode:

During normal TX mode, the transmitter's IF PLL is opened for modulation of the current controlled oscillator (ICO) for a

short period of time (0.4 to 3ms). For development purposes, open-loop modulation may be performed for an indefinite

period of time by externally supplying the required ICO control voltage. This allows the ICO to maintain a locked condi-

tion.

Transmitter Test Mode utilizes the LPO pin, which is switched to the output of the internal loop filter of the transmitter’s IF

ICO when Set_Tx_PLL_LF_Ext (Register 7, Bit 15) is set high and the 3.2kHz/32kHz low power oscillator is not in use.

This pin may be used either to monitor the control voltage during a packet transmission or to externally supply the control

voltage for an extended or continuous transmission. When monitoring the ICO control voltage, the voltage on the LPO

pin will drift from its initial voltage as the transmission time increases, but should remain in the range of 0.7V to 0.9V.

When supplying the ICO control voltage, the voltage to be applied to the LPO pin should be equal to the initial voltage

measured when monitoring.

11-136

Rev A13 010912

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