CC1021-RTR1 datasheet(18/92 Pages) TI

18 / 92 page

CC1021

SWRS045

Page 18 of 91

Application Circuit

Very

few

external

components

are

required for the operation of CC1021. The

recommended application circuit is shown

in Figure 3. The external components are

described in Table 12 and values are

given in Table 13.

Input / output matching

L1 and C1 is the input match for the

receiver. L1 is also a DC choke for

biasing. L2 and C3 are used to match the

transmitter to 50 Ω.

Internal circuitry

makes it possible to connect the input and

output together and match the CC1021 to

50 Ω in both RX and TX mode. However, it

is recommended to use an external T/R

switch for optimum performance.

See

section 14 on page 46 for details.

Component values for the matching

network are easily found using the

SmartRF Studio software.

Bias resistor

The precision bias resistor R1 is used to

set an accurate bias current.

PLL loop filter

The loop filter consists of two resistors (R2

and R3) and three capacitors (C6-C8). C7

and C8 may be omitted in applications

where high loop bandwidth is desired. The

values shown in Table 13 are optimized

for 38.4 kBaud data rate. Component

values for other data rates are easily found

using the SmartRF Studio software.

Crystal

An external crystal with two loading

capacitors (C4 and C5) is used for the

crystal oscillator. See section 19 on page

58 for details.

Additional filtering

Additional external components (e.g. RF

LC or SAW filter) may be used in order to

improve the performance in specific

applications. See section 14 on page 46

for further information.

Power supply decoupling and filtering

must be used (not shown in the application

circuit). The placement and size of the

decoupling capacitors and the power

supply filtering are very important to

achieve the optimum performance for

narrowband

applications.

Chipcon

provides a reference design that should be

followed very closely.

Ref

Description

LNA input match and DC block, see page 46

PA output match and DC block, see page 46

Crystal load capacitor, see page 58

PLL loop filter capacitor

PLL loop filter capacitor (may be omitted for highest loop bandwidth)

C60

Decoupling capacitor

LNA match and DC bias (ground), see page 46

PA match and DC bias (supply voltage), see page 46

Precision resistor for current reference generator

PLL loop filter resistor

R10

PA output match, see page 46

XTAL

Crystal, see page 58

Table 12. Overview of external components (excluding supply decoupling capacitors)

CC1021-RTR1 Datasheet(PDF) 18 Page - Texas Instruments

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