CC1010-RTY1 datasheet(126/152 Pages) TI

126 / 152 page

CC1010

SWRS047

Page 126 of 152

17.20 RSSI Output

CC1010 has a built-in RSSI (Received

Signal Strength Indicator) giving an analog

output signal at the AD2(RSSI/IF) pin.

RSSI

enabled

when

setting

FREND.RSSI (see page 119). The output

current of this pin is then inversely

proportional to the input signal level. The

output should be terminated in a resistor to

convert the current output into a voltage. A

capacitor is used to low-pass filter the

signal.

The RSSI voltage range is from 0 – 1.2 V

when using a 27 k

Ω terminating resistor,

giving approximately 50 dB/V. This RSSI

voltage can be measured by the on-chip

A/D converter using the AD2 input. Note

that a higher voltage means a lower input

signal.

The RSSI measures the power referred to

the RF_IN pin. The input power can be

calculated using the following equations:

P = -48.8 VRSSI– 57.2 [dBm] at 433 MHz

P = -46.9 VRSSI– 53.9 [dBm] at 868 MHz

The external network for RSSI operation is

shown in

Figure 41. R281 = 27 k

Ω, C281 = 1nF.

A typical plot of RSSI voltage as function

of input power is shown in Figure 42.

When using the on-chip A/D converter, set

ADCON = 0x06 to initiate a single

conversion using VDD as reference. The

converted RSSI voltage can then be read

from the ADDATH and ADDATL registers.

CC1010

AD2 (RSSI/IF)

C281

R281

Figure 41. RSSI circuit

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,1

1,2

1,3

-105 -100 -95

-90

-85

-80

-75

-70

-65

-60

-55

-50

dBm

433Mhz

868Mhz

Figure 42. Typical RSSI voltage vs. input

power

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