CC1100-RTY1 datasheet(19/100 Pages) TI1

19 / 100 page

CC1100

SWRS038D

Page 19 of 92

Application Circuit

Only a few external components are required

for using the

CC1100. The recommended

application circuits are shown in Figure 3 and

Figure 4. The external components are

described in Table 14, and typical values are

given in Table 15.

Bias Resistor

The bias resistor R171 is used to set an

accurate bias current.

Balun and RF Matching

The components between the RF_N/RF_P

pins and the point where the two signals are

joined together (C131, C121, L121 and L131

for the 315/433 MHz reference design [5].

L121, L131, C121, L122, C131, C122 and

L132 for the 868/915 MHz reference design

[6]) form a balun that converts the differential

RF signal on

CC1100 to a single-ended RF

signal. C124 is needed for DC blocking.

Together with an appropriate LC network, the

balun

components

also

transform

the

impedance to match a 50

Ω antenna (or

cable). Suggested values for 315 MHz, 433

MHz, and 868/915 MHz are listed in Table 15.

The balun and LC filter component values and

their placement are important to keep the

performance

optimized.

highly

recommended to follow the CC1100EM

reference design [5] and [6].

Crystal

The crystal oscillator uses an external crystal

with two loading capacitors (C81 and C101).

See Section 27 on page 53 for details.

Additional Filtering

Additional external components (e.g. an RF

SAW filter) may be used in order to improve

the performance in specific applications.

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

CC1100EM reference design ([5] and [6])

should be followed closely.

Component

Description

C51

Decoupling capacitor for on-chip voltage regulator to digital part

C81/C101

Crystal loading capacitors, see Section 27 on page 53 for details

C121/C131

RF balun/matching capacitors

C122

RF LC filter/matching filter capacitor (315 and 433 MHz). RF balun/matching

capacitor (868/915 MHz).

C123

RF LC filter/matching capacitor

C124

RF balun DC blocking capacitor

C125

RF LC filter DC blocking capacitor (only needed if there is a DC path in the antenna)

L121/L131

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

L122

RF LC filter/matching filter inductor (315 and 433 MHz). RF balun/matching inductor

(868/915 MHz). (inexpensive multi-layer type)

L123

RF LC filter/matching filter inductor (inexpensive multi-layer type)

L124

RF LC filter/matching filter inductor (inexpensive multi-layer type)

L132

RF balun/matching inductor. (inexpensive multi-layer type)

R171

Resistor for internal bias current reference.

XTAL

26MHz - 27MHz crystal, see Section 27 on page 53 for details.

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

CC1100-RTY1 Datasheet(PDF) 19 Page - Texas Instruments

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