CC1070-RTY1 datasheet(13/57 Pages) TI

13 / 57 page

CC1070

SWRS043

Page 13 of 58

Circuit Description

BIAS

LOCK

PDO

DCLK

FREQ

SYNTH

DIGITAL

MODULATOR

- Modulation

- Data shaping

- Power Control

Power

Control

DIGITAL

INTERFACE

µC

RF_OUT

R_BIAS

XOSC_Q1 XOSC_Q2

XOSC

CHP_OUT

Multiplexer

PCLK

PDI

PSEL

Figure 2.

CC1070 simplified block diagram

A simplified block diagram of

CC1070 is

shown in Figure 2. Only signal pins are

shown.

During transmit operation, the synthesized

RF frequency is fed directly to the power

amplifier (PA). The RF output is frequency

shift keyed (FSK) by the digital bit stream

that is fed to the DI pin. Optionally, the

internal Gaussian filter can be enabled for

Gaussian FSK (GFSK).

The frequency synthesizer includes a

completely on-chip LC VCO. The VCO

operates in the frequency range 1.608-

1.880 GHz. The CHP_OUT pin is the

charge pump output and VC is the control

node of the on-chip VCO. The external

loop filter is placed between these pins. A

crystal is to be connected between

XOSC_Q1 and XOSC_Q2. A lock signal is

available from the PLL.

The 4-wire SPI serial interface is used for

configuration.

Application Circuit

Very

few

external

components

are

required for the operation of

CC1070. A

typical application circuit is shown in

Figure 3. The external components are

described in Table 9 and values are given

in Table 10.

Output matching

L2, C2 and C3 are used to match the

transmitter to 50

Ω. See section 13 on

page 26 for details. Component values for

the matching network are easily calculated

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 10 can be used for

data rates up to 4.8 kBaud. Component

values for higher 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 17 on page

34 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 13 on page 26

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

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