CC2500-RTR1 datasheet(18/96 Pages) TI

18 / 96 page

CC2500

SWRS040C

Page 18 of 89

balun that converts the differential RF signal

CC2500 to a single-ended RF signal. C121

and C131 are needed for DC blocking.

Together with an appropriate LC network, the

balun

components

also

transform

the

impedance to match a 50

 antenna (or

cable). Suggested values are listed in Table

15.

The balun and LC filter component values and

their placement are important to keep the

performance

optimized.

highly

recommended

the

CC2500EM

reference design ([4]).

Crystal

The crystal oscillator uses an external crystal

with two loading capacitors (C81 and C101).

See Section 26 on page 50 for details.

Power Supply Decoupling

The power supply must be properly decoupled

close to the supply pins. Note that decoupling

capacitors are not shown in the application

circuit. The placement and the size of the

decoupling capacitors are very important to

achieve

the

optimum

performance.

The

CC2500EM reference design ([4]) should be

followed closely.

Component

Description

C51

Decoupling capacitor for on-chip voltage regulator to digital part

C81/C101

Crystal loading capacitors, see Section 26 on page 50 for details

C121/C131

RF balun DC blocking capacitors

C122/C132

RF balun/matching capacitors

C123/C124

RF LC filter/matching capacitors

L121/L131

RF balun/matching inductors (inexpensive multi-layer type)

L122

RF LC filter inductor (inexpensive multi-layer type)

R171

Resistor for internal bias current reference

XTAL

26-27 MHz crystal, see Section 26 on page 50 for details

Table 14: Overview of External Components (excluding supply decoupling capacitors)

Antenna

(50 Ohm)

1.8V-3.6V power supply

1 SCLK

2 SO (GDO1)

3 GDO2

4 DVDD

5 DCOUPL

AVDD 15

AVDD 14

RF_N 13

RF_P 12

AVDD 11

XTAL

C122

C132

L131

L121

L122

C123

C124

R171

C81

C101

C51

CSn

GDO0

(optional)

GDO2

(optional)

(GDO1)

SCLK

CC2500

DIE ATTACH PAD:

C131

C121

Alternative:

Folded dipole PCB

antenna (no external

components needed)

Figure 3: Typical Application and Evaluation Circuit (excluding supply decoupling capacitors)

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