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RF2513 Schematic ( PDF Datasheet ) - RF Micro Devices

Teilenummer RF2513
Beschreibung UHF TRANSMITTER
Hersteller RF Micro Devices
Logo RF Micro Devices Logo 




Gesamt 14 Seiten
RF2513 Datasheet, Funktion
11
Typical Applications
• Single- or Dual-Channel LO Source
• FM/FSK Transmitter
• Wireless Data Transmitters
RF2513
UHF TRANSMITTER
• 433/868/915MHz ISM Band Systems
• Wireless Security Systems
Product Description
The RF2513 is a monolithic integrated circuit intended for
use as a low-cost frequency synthesizer and transmitter.
The device is provided in a 24 pin SSOP package and is
designed to provide a phased locked frequency source
for use in local oscillator or transmitter applications. The
chip can be used in FM or FSK applications in the U.S.
915MHz ISM band and European 433MHz or 868MHz
ISM band. The integrated VCO, dual-modulus/dual-divide
(128/129 or 64/65) prescaler, and reference oscillator
require only the addition of an external crystal to provide
a complete phase-locked oscillator. A second reference
oscillator is available to support two channel applications.
0.157
0.150
1
0.344
0.337
0.012
0.008
0.025
0.2440
0.2284
8°MAX
0°MIN
0.0098
0.0040
0.0688
0.0532
0.050 0.0098
0.016 0.0075
Optimum Technology Matching® Applied
üSi BJT
GaAs HBT
GaAs MESFET
Si Bi-CMOS
SiGe HBT
Si CMOS
7 16 18 20 22 23 13
Gain
Control
TX OUT 8
Phase
Detector &
Charge Pump
Prescaler
128/129 or
64/65
321
Ref.
Select 24 OSC SEL
12 PRESCL OUT
14 MOD CTRL
15 DIV CTRL
Functional Block Diagram
Package Style: SSOP-24
Features
• Fully Integrated PLL Circuit
• 10mW Output Power at 433MHz
• 2.7V to 5.0V Supply Voltage
• Low Current and Power Down Capability
• 300MHz to 1000MHz Frequency Range
• Narrowband and Wideband FM
Ordering Information
RF2513
UHF Transmitter
RF2513 PCBA-L Fully Assembled Evaluation Board, 433MHz
RF2513 PCBA-M Fully Assembled Evaluation Board, 868MHz
RF2513 PCBA-H Fully Assembled Evaluation Board, 915MHz
RF Micro Devices, Inc.
7625 Thorndike Road
Greensboro, NC 27409, USA
Tel (336) 664 1233
Fax (336) 664 0454
http://www.rfmd.com
11
Rev B8 010509
11-23






RF2513 Datasheet, Funktion
RF2513
11
the charge pump to create a control voltage for the
voltage controlled oscillator.
The voltage controlled oscillator (VCO) is a tuned
differential amplifier with the bases and collectors
cross-coupled to provide positive feedback and a 360°
phase shift. The tuned circuit is located in the collec-
tors. It is comprised of internal varactors and two exter-
nal inductors. The designer selects the inductors for
the desired frequency of operation. These inductors
also provide DC bias for the VCO. The output of the
VCO is buffered and applied to the prescaler circuit,
where it is divided down and compared to the refer-
ence oscillator frequency.
The PLL and VCO circuitry can be enabled by setting
applying a “high” logic level to pin 4 (PLL ENABL).
Conversely, the PLL and VCO circuitry will be turned
off if the level is tied “low”.
The transmit amplifier is a two stage amplifier con-
sisting of a driver and an open collector final stage. It is
capable of providing 8dBm of output power into a 50
load while operating from a 3.6V power supply.
The output power is adjustable by the setting of pin 7
(LVL ADJ). This analog input allows the designer a
15dB range of output power. As the LVL ADJ voltage is
reduced, the output power and current consumption
are reduced. LVL ADJ must be low when the transmit-
ter is disabled.
Additionally, the transmitter circuitry can be disabled
entirely by applying a “low” logic level to pin 11 (TX
ENABL). During transmission, this pin should be tied
“high”. This pin controls all circuitry except for the PLL
circuitry.
During transmission the transmitter is enabled and the
impedance of the output pin, pin 8 (TX OUT), is low.
When the transmitter is not enabled, the impedance
becomes high.
The RF2513 contains onboard band gap reference
voltage circuitry which provides a stable DC bias over
varying temperature and supply voltages.
Designing with the RF2513
The reference oscillator is built around the onboard
transistor at pins 1, 2 and 3. The intended topology is
of a Colpitts oscillator. The Colpitts oscillator is quite
common and requires few external components, mak-
ing it ideal for low cost solutions. The topology of this
type of oscillator is as seen in the following figure.
11-28
VCC
C2
X1
C1
This type of oscillator is a parallel resonant circuit for a
fundamental mode crystal. The transistor amplifier is
an emitter follower and the voltage gain is developed
by the tapped capacitor impedance transformer. The
series combination of C1 and C2 act in parallel with the
input capacitance of the transistor to capacitively load
the crystal.
The nominal capacitor values can be calculated with
the following equations.
C1
=
6---0--------C----l--o---a--d-
freqMHz
and
C2 =
------------1--------------
------1------- --1----
Cload C1
The load capacitance is usually 32pF. The variable freq
is the oscillator frequency in MHz. The frequency can
be adjusted by either changing C2 or by placing a vari-
able capacitor in series with the crystal. As an exam-
ple, assume a desired frequency of 14MHz and a load
capacitance of 32pF. C1=137.1pF and C2=41.7pF.
These capacitor values provide a starting point. The
drive level of the oscillator should be checked by look-
ing at the signal at pin 2 (OSC E). It has been found
that the level at this pin should generally be around
500mVPP or less. This will reduce the reference spur
levels and reduce noise from distortion. If this level is
higher than 500mVPP then decrease the value of C1.
The values of these capacitors are usually tweaked
during design to meet performance goals, such as
minimizing the start-up time.
Additionally, by placing a variable capacitor in series
with the crystal, one is able to adjust the frequency.
This will also alter the drive level, so it should be
checked again.
An important part of the overall design is the voltage
controlled oscillator (VCO). The VCO is configured as
a differential amplifier. The VCO is tuned via the exter-
nal inductors, capacitor and varactor. The varactor
capacitance is set by the loop filter output voltage
through a 4kresistor.
Rev B8 010509

6 Page









RF2513 pdf, datenblatt
RF2513
Evaluation Board Layout 433MHz
Board Size 2.0” x 2.0”
Board Thickness 0.031”, Board Material FR-4
Evaluation Board Layout 868MHz
Board Size 2.0” x 2.0”
11
Evaluation Board Layout 915MHz
Board Size 2.0” x 2.0”
11-34
Rev B8 010509

12 Page





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