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PDF EVB72035 Data sheet ( Hoja de datos )
| Número de pieza | EVB72035 | |
| Descripción | 868/915MHz FSK/ASK Transmitter Evaluation Board Description | |
| Fabricantes | Melexis Microelectronic Systems | |
| Logotipo |  |
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EVB72035
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
Features
! Fully integrated PLL-stabilized VCO
! Frequency range from 850 MHz to 930 MHz
! Single-ended RF output
! FSK through crystal pulling allows modulation
from DC to 40 kbit/s
! High FSK deviation possible for wideband data
transmission
! ASK achieved by on/off keying of internal
www.DataSheet4U.copmower amplifier up to 40 kbit/s
! Wide power supply range from 1.95 V to 5.5 V
! Very low standby current
! On-chip low voltage detector
! High over-all frequency accuracy
! FSK deviation and center frequency independ-
ently adjustable
! Adjustable output power range from
-12 dBm to +9.5 dBm (at connector board)
! Adjustable effective radiated power (ERP) range
from -27 dBm to -6 dBm (at antenna board)
! Adjustable current consumption from
3.9 mA to 13.4 mA
! Conforms to EN 300 220 and similar standards
Ordering Information
Part No. (see paragraph 6)
EVB72035-868-FSK-A
EVB72035-868-FSK-C (on request)
EVB72035-915-FSK-A
EVB72035-915-FSK-C (on request)
Note 1: EVB default population is FSK, ASK modifications according to section 3.1 and 4.1.
Note 2: EVB72035 is applicable for devices TH72035, TH72031 and TH72032.
Application Examples
!
! General digital data transmission
! Tire Pressure Monitoring Systems (TPMS)
! Remote Keyless Entry (RKE)
! Wireless access control
! Alarm and security systems
! Garage door openers
! Remote Controls
! Home and building automation
! Low-power telemetry systems
Evaluation Board Example
General Description
The TH72035 evaluation board is designed to demonstrate the performance of the transmitter IC with an
on-board loop antenna. This board allows the user to setup an RF transmitter very easily. Alternatively a
50 Ohm connector board can be requested.
39012 72035 01
Rev. 007
Page 1 of 14
EVB Description
June/07
1 page  
EVB72035
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
2.4 ASK Modulation
The PLL transmitter can be ASK-modulated by
applying a data stream directly at the pin
ASKDTA. This turns the internal current
sources of the power amplifier on and off and
therefore leads to an ASK signal at the output.
ASKDTA
0
1
Description
Power amplifier is turned off
Power amplifier is turned on (according
to the selected output power step)
www.DataSheet24U.5.comOutput Power Selection
The transmitter is provided with an output power selection feature. There are four predefined output power
steps and one off-step accessible via the power selection pin PSEL. A digital power step adjustment was
chosen because of its high accuracy and stability. The number of steps and the step sizes as well as the
corresponding power levels are selected to cover a wide spectrum of different applications.
The implementation of the output power control
logic is shown in figure 4. There are two
matched current sources with an amount of
about 8 µA. One current source is directly ap-
plied to the PSEL pin. The other current source
is used for the generation of reference voltages
with a resistor ladder. These reference voltages
are defining the thresholds between the power
steps. The four comparators deliver thermome-
ter-coded control signals depending on the
voltage level at the pin PSEL. In order to have a
certain amount of ripple tolerance in a noisy
environment the comparators are provided with
a little hysteresis of about 20 mV. With these
control signals, weighted current sources of the
power amplifier are switched on or off to set the
desired output power level (Digitally Controlled
Current Source). The LOCK, ASK signal and
the output of the low voltage detector are gating
this current source.
RPS
PSEL
ASKDTA &
&
&&&
OUT
Fig. 4: Block diagram of output power control circuitry
There are two ways to select the desired output power step. First by applying a DC voltage at the pin PSEL,
then this voltage directly selects the desired output power step. This kind of power selection can be used if
the transmission power must be changed during operation. For a fixed-power application a resistor can be
used which is connected from the PSEL pin to ground. The voltage drop across this resistor selects the de-
sired output power level. For fixed-power applications at the highest power step this resistor can be omitted.
The pin PSEL is in a high impedance state during the “TX standby” mode.
2.6 Lock Detection
The lock detection circuitry turns on the power amplifier only after PLL lock. This prevents from unwanted
emission of the transmitter if the PLL is unlocked.
2.7 Low Voltage Detection
The supply voltage is sensed by a low voltage detect circuitry. The power amplifier is turned off if the supply
voltage drops below a value of about 1.85 V. This is done in order to prevent unwanted emission of the
transmitter if the supply voltage is too low.
39012 72035 01
Rev. 007
Page 5 of 14
EVB Description
June/07
5 Page 
EVB72035
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
5 Evaluation Board Layouts
5.1 Antenna Board
Board layout data in Gerber format are available, board size is 32mm x 38mm x 1mm FR4.
www.DataSheet4U.com
small
PCB top view
EVB720X5_ANT_L (2)
PCB bottom view
5.2 PCB Loop Antenna Dimensions
Fig. 8: Circular loop
Loop Dimension
mm
A
16
B
8
Fig. 9: Square loop equivalent
2a a b r w
17 8.5
5
4
2
39012 72035 01
Rev. 007
Page 11 of 14
EVB Description
June/07
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet EVB72035.PDF ] | |
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