CC2480 datasheet(33/48 Pages) TI

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CC2480

10.7

Linear IF and AGC Settings

CC2480 is based on a linear IF chain where the

signal amplification is done in an analog VGA

(variable gain amplifier). The gain of the VGA

is digitally controlled.

The AGC (Automatic Gain Control) loop

ensures that the ADC operates inside its

dynamic range by using an analog/digital

feedback loop.

10.8

Clear Channel Assessment

The clear channel assessment signal is based

the

measured

RSSI

value

and

programmable threshold. The clear channel

assessment function is used to implement the

CSMA-CA functionality specified in [1]. CCA is

valid when the receiver has been enabled for

at least 8 symbol periods.

10.9

VCO and PLL Self-Calibration

10.9.1

VCO

The VCO is completely integrated and

operates at 4800 – 4966 MHz. The VCO

frequency is divided by 2 to generate

frequencies in the desired band (2400-2483.5

MHz).

10.9.2

PLL self-calibration

The VCO's characteristics will vary with

temperature, changes in supply voltages, and

the desired operating frequency.

In order to ensure reliable operation the VCO’s

bias

current

and

tuning

range

are

automatically calibrated every time the RX

mode or TX mode is enabled.

10.10 Input / Output Matching

The RF input / output is differential (RF_N and

RF_P

). In addition there is supply switch output

pin (TXRX_SWITCH) that must have an

external DC path to RF_N and RF_P.

In RX mode the TXRX_SWITCH pin is at

ground and will bias the LNA. In TX mode the

TXRX_SWITCH

pin is at supply rail voltage and

will properly bias the internal PA.

The RF output and DC bias can be done using

different topologies. Some are shown in Figure

5 on page 21.

Component values are given in Table 19 on

page

22.

differential

antenna

implemented, no balun is required.

If a single ended output is required (for a

single ended connector or a single ended

antenna), a balun should be used for optimum

performance.

CC2480 Data Sheet SWRS074

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