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Número de pieza | TH72036 | |
Descripción | FSK/ASK Transmitter | |
Fabricantes | Melexis | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de TH72036 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
No Preview Available ! TH72036
868/915MHz
FSK/ASK Transmitter
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
power amplifier up to 40 kbit/s
! Wide power supply range from 1.95 V to 5.5 V
! Very low standby current
! Microcontroller clock output
! On-chip low voltage detector
! High over-all frequency accuracy
! FSK deviation and center frequency
independently adjustable
! Adjustable output power range from
-11 dBm to +9.5 dBm
! Adjustable current consumption from
5.5 mA to 13.8 mA
! Conforms to EN 300 220 and similar standards
! 10-pin Quad Flat No-Lead Package (QFN)
YOrdering Information
RPart Number
Temperature Code
INATH72036
K (-40 °C to 125 °C)
Package Code
LD (10L QFN 3x3 Dual)
Delivery Form
120 pc/tray
5000 pc/T&R
ELIMApplication Examples
PR! General digital data transmission
Pin Description
! Tire Pressure Monitoring Systems (TPMS)
! Remote Keyless Entry (RKE)
top bottom
! Wireless access control
! Alarm and security systems
! Garage door openers
! Remote Controls
! Home and building automation
FSKDTA
FSKSW
ROI
EN
CKOUT
TH72036
VCC
VEE
OUT
CKDIV
PSEL
10
9
8
7
6
1
2
3
4
5
! Low-power telemetry systems
General Description
The TH72036 FSK/ASK transmitter IC is designed for applications in the European 868 MHz industrial-
scientific-medical (ISM) band, according to the EN 300 220 telecommunications standard. It can also be
used for any other system with carrier frequencies ranging from 850 MHz to 930 MHz (e.g. for applications in
the US 902 to 928 MHz ISM band).
The transmitter's carrier frequency fc is determined by the frequency of the reference crystal fref. The inte-
grated PLL synthesizer ensures that carrier frequencies, ranging from 850 MHz to 930 MHz, can be
achieved. This is done by using a crystal with a reference frequency according to: fref = fc/N, where N = 32 is
the PLL feedback divider ratio.
A clock signal with selectable frequency is provided. It can be used to drive a microcontroller.
3901072036
Rev. 005
Page 1 of 16
Data Sheet
June/07
1 page TH72036
868/915MHz
FSK/ASK Transmitter
2.4 ASK Modulation
The TH72036 can be ASK-modulated by applying data directly at pin PSEL. This turns the PA on and off
which leads to an ASK signal at the output.
2.5 Output 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
Ywith a resistor ladder. These reference voltages
Rare defining the thresholds between the power
steps. The four comparators deliver thermome-
Ater-coded control signals depending on the
INvoltage level at the pin PSEL. In order to have a
certain amount of ripple tolerance in a noisy
IMenvironment the comparators are provided with
a little hysteresis of about 20 mV. With these
Lcontrol signals, weighted current sources of the
power amplifier are switched on or off to set the
Edesired output power level (Digitally Controlled
RCurrent Source). The LOCK, ASK signal and
Pthe output of the low voltage detector are gating
RPS
PSEL
&
&
&&&
OUT
Fig. 4: Block diagram of output power control circuitry
this current source.
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.
3901072036
Rev. 005
Page 5 of 16
Data Sheet
June/07
5 Page 4.6 AC Characteristics
TH72036
868/915MHz
FSK/ASK Transmitter
Power step
0
1
2
3
4
RPS / kΩ
<3
22
56 120 not connected
4.7 Output Power Steps – ASK Mode
typical values at TA = 23 °C and VCC = 3 V; test circuit shown in Fig. 6
Power step
1
2
YRPS / kΩ
2.4
2.8
RR1 / kΩ
36
14
3
3.5
7
4
not connected
0
LIMINAVPSlow = voltage across RPS if ASK_DTA at 0V
PREVPShigh = voltage across RPS if ASK_DTA at Vcc
V PSlow
RPS
R1
PSEL 6
RPS
V PShigh
R1
PSEL 6
Vcc
If the transmitter is operated at any supply voltage Vcc, the values for R1 and RPS can be calculated as fol-
lows:
R1
=
VCC ⋅VPSlow
I PSEL ⋅VPShigh
RPS
=
R1
VPShigh
VCC − VPShigh
3901072036
Rev. 005
Page 11 of 16
Data Sheet
June/07
11 Page |
Páginas | Total 16 Páginas | |
PDF Descargar | [ Datasheet TH72036.PDF ] |
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