Page 1
Features
! Fully integrated, PLL-stabilized VCO
! Flexible frequency range from 800 MHz to 930 MHz
! ASK achieved by on/off keying of internal
power amplifier
! FM possible with external varactor
! Wide power supply range from 2.2 V to 5.5 V
! High over-all frequency accuracy
! Very low standby current
TH71082
868/915MHz
ASK Transmitter / LO Source
! Adjustable output power range from
-18 dBm to -2 dBm
! Adjustable current consumption from
6.2 mA to 12.5 mA
! Single-ended RF output
! Clock output for µC drive
! Conforms to EN 300 220 and similar
standard
Ordering Information
Part No. Temperature Range Package
TH71082 -40 C° to 85 °C SOIC8
Application Examples Pin Description
! Keyless car and central locking
! Low-power telemetry
! Alarm and security systems
! General digital data transmission
! General analog audio signal transmission
! Local oscillator signal gener ation
LF
RO
ENTX
CKOUT
1
2
3
4
TH71082
VEE
8
7
OUT
6
VCC
PS/DATA
5
TH71082 Data Sheet Page 1 of 10 Dec. 2001
3901071082 Rev. 004
Page 2
General Description
TH71082
868/915MHz
ASK Transmitter / LO Source
The TH71082 ASK transmitter IC is designed for
applications in the European 868MHz industrialscientific-m edical (ISM) band, according to the EN
300 220 telecommunications standard. It can also
be used for any other system with carrier
frequencies ranging from 800 MHz to 930 MHz
(e.g. for applications in the US 915MHz ISM band).
Theory of Operation
General
As depicted in Fig.1, the TH71082 transmitter
consists of a fully integrated voltage-controlled
oscillator (VCO), a divide-by-32 divider (div32), a
phase-frequency detector (PFD) and a charge
pump. An external loop filter at pin LF determines
the dynamic behavio ur of the PLL and suppres ses
reference spurious signals.
The VCO’s output signal fee ds the power amplifier
(PA). RF signal power P
steps from P
= –15 dBm to -1 dBm, either by
o
changing the valu e of resistor R
voltage V
at pin PS/DATA. The open-collector
PS
output (OUT) can be used to either drive a loop
antenna or to feed a single-ended load impedanc e.
This could be, for example
or a 50Ω output port. In any case, an impedance
matching network should be added in order to
achieve maximum available RF power.
Bandgap biasing ensures stab le operation of the IC
at a power supply range of 2.2 V to 5.5 V.
Clock Output
The TH71082 feature a clock output (CKOUT) that
can be used to drive a µC. The frequency at
CKOUT is f
/8. The clock output is sle w-rate l imited
ref
in order to keep sp urious signal em ission as low as
possible. The voltag e swing at CKOUT depends on
the capacitive loading at this pin.
It is approximate 2 V
can be adjusted in six
o
or by varying the
1
λ
/4 monopol antenna
pp
at C
load
= 5 pF
The transmitter's c arrier frequency f
by the frequency of the reference crystal f
is determined
c
that is
ref
used. The integrated P LL synthesizer ensur es that
each RF value, ranging fr om 800 MHz to 9 30 MHz,
can be achieved by using a cr ystal with reference
frequency accordin g to: f
= fc/N, where N = 32 is
ref
the PLL feedback divider ratio.
ASK Modulation
The TH71082 can be ASK-modulated by applying
data directly at pin PS. This turns the PA on and off
and therefore leads to an ASK signal at the output.
LO Source
Many applications require a stable RF source. For
this purpose, the TH71082 can be used without
modulation as an easy-to-use, PLL-stabilized,
continuous wave (CW) generator.
Frequency Modulation (FM)
For FM operation an external varactor is required. It
simply acts as a pulling capacitor connected in
series to the crystal. Then the analog modulation
signal, applied through a series resistor, directly
modulates the XOSC.
Mode Control Logic
The mode control logic allows two different modes
of operation as listed in the following table. The
mode control pin ENTX is pulled-down internally.
This guarantees that th e whole circuit is shut down
if this pin is left floating.
ENTX Mode Description
0 TX disabled whole circuit in standby
1 TX enable TX active
Table 1: Modes of operation
TH71082 Data Sheet Page 2 of 10 Dec. 2001
3901071082 Rev. 004
Page 3
Block Diagram
TH71082
868/915MHz
ASK Transmitter / LO Source
7
OUT
VCC
5
PS/DATA
6
VCC
4
PA
div32
div 8
PFD
XOSC
VCO
ENTX
3
mode
control
charge
8 VEE
pump
CF2
1
LF
RF1
CF1
CKOUT
2
RO
XTAL
CX1
Fig. 1: TH71082 block diagram with external components
TH71082 Data Sheet Page 3 of 10 Dec. 2001
3901071082 Rev. 004
Page 4
TH71082
868/915MHz
ASK Transmitter / LO Source
Pin Definition and Descripti on
Pin No. Name I/O Type Functional Schematic Description
1 LF analog I/O
2 RO analog I/O
3 ENTX input
4 CKOUT output
LF
1
ENTX
RO1
2
3
CKOUT
connection to loop filter,
charge pump output,
200
Ω
200
Ω
5p
VCO tuning input
XOSC connection to XTAL,
37k
Colpitts type crystal
oscillator
28p
28p
mode control input, CMOScompatible with internal pull-
1.1k
down
clock output,
CMOS-compatible
Ω
200
4
5 PS/DATA analog I/O
PS/DATA
5
200
20µA
Ω
power-select and ASK input,
high-impedance comparator
logic
6 VCC supply positive power supply
7 OUT output
VCC
VCC
Power amplifier output,
open collector
OUT
7
VEE
VEE
8 VEE ground negative power supply
TH71082 Data Sheet Page 4 of 10 Dec. 2001
3901071082 Rev. 004
Page 5
Technical Data
Absolute Maximum Ratings
Parameter Symbol Condition Min Max Unit
TH71082
868/915MHz
ASK Transmitter / LO Source
Supply voltage V
Input voltage V
Input current I
Storage temperature T
Electrostatic discharge V
Normal Operating Conditions
Parameter Symbol Condition Min Max Unit
Supply voltage V
Operating temperature T
XOSC frequency f
VCO frequency f
Clock frequency f
DC Characteristics
cc
in
in
STG
ESD
cc
a
ref
c
clk
-0.3 7.0 V
ENTX pin -0.3 VCC+0.3 V
ENTX pin -1.0 1.0 mA
-40 150 °C
human body model,
-1.0 +1.0 kV
MIL STD 833D
method 3015.7
2.2 5.5 V
-40 85 °C
set by the crystal 25 29 MHz
fc = 32 • f
f
= f
/ 4 3.12 3.62 MHz
clk
ref
ref
800 930 MHz
all parameters under normal operating conditions, unless otherwise stated;
typical values at T
= 23 °C and Vcc = 3 V
a
Parameter Symbol Condition Min Typ Max Unit
Standby current I
Operating current I
Input HIGH voltage V
Input LOW voltage V
Input current I
Pull down current I
SBY
cc
HIGH
LOW
in
pd
ENTX=0 0.05 0.1 µA
ENTX=1, VPS=1.1V 8 10 11 mA
ENTX pin 0.7*V
cc
ENTX pin -0.3 0.3*V
Vcc+0.3 V
cc
V
ENTX=0 -1 1 µA
ENTX=1 2 8 15 µA
TH71082 Data Sheet Page 5 of 10 Dec. 2001
3901071082 Rev. 004
Page 6
ASK Transmitter / LO Source
AC Characteristics
all parameters under normal operating conditions, unless otherwise stated;
typical values at T
ENTX = 1, V
Parameter Symbol Condition Min Typ Max Unit
= 23 °C and Vcc = 3 V;
a
= 1.1V, fc = 868.3 MHz, test circuit shown in Fig. 2
PS
TH71082
868/915MHz
Output power P
FM deviation
Modulation frequency FM f
Data rate ASK R
∆f
mod
ASK
Reference spurs P
Harmonic content P
harm
Spurious output signal P
Phase noise PN
VCO gain K
Charge pump current I
Clock voltage swing V
Start-up time t
VCO
CP
CKOUT
on
FM
ref
off
o
adjustable with
varactor and V
@ fc ± f
ref
@ 2fc , 3fc , 4f
≤ 0.1V
V
PS
± 500kHz
@ f
c
C
= 5pF 2 V
load
FM
c
from ”all OFF” to any
-4 dBm
±6
5kHz
40 kbit/s
-44 dBm
-40 dBm
-60 dBm
-87 dBc/Hz
300 MHz/V
±260
0.9 ms
other mode
Output Power Selection
typical values at T
ENTX = 1, f
R1 / kΩ
R2 / kΩ
Ω
Ω Ω
Ω
Ω Ω
c
VPS / V
= 23 °C and Vcc = 3 V:
a
= 868.3 MHz, test circuit shown in Fig. 2
0 7.5 11 15 24 43
4.7 4.7 4.7 4.7 4.7
≥≥≥≥ 2
1.1 0.9 0.7 0.5 0.3
Icc / mA 12.5 9.5 8.5 7.8 7.0 6.2
Po / dBm -2 -5 -8 -11 -15 -18
P
harm
/ dBm
≤-40 ≤-40 ≤-40 ≤-45 ≤-45 ≤-50
kHz
µA
pp
If the transmitter is operated at any supply voltage Vcc,
the values for R
and R2 can be calculated as allows:
1
V
RR
21
V
cc
−•= 1
PS
Crystal Parameter
Parameter Symbol Condition Min Max Unit
Crystal frequency f
Load capacitance C
Static capacitance C
Resonance resistance R
Spurious response a
crystal
load
0
m
spur
TH71082 Data Sheet Page 6 of 10 Dec. 2001
3901071082 Rev. 004
fundamental mode, AT 25 29 MHz
10 15 pF
7pF
40
Ω
-10 dB
Page 7
Test Circuit
TH71082
868/915MHz
ASK Transmitter / LO Source
Fig. 2: Test circuit for ASK
with 50Ω matching network
Test circuit component list to Fig. 2
OUT
C2
RF1
CF1CF2
8
1
C1
VEE
LF
CX
7
OUT
RO
2
XT AL
L1L2
6
3
12 3
VCC
C3
5
PS
VCC
DATA
R2
ENTX
1
GND
ENTX
R1
CKOUT
4
C4
1
2
1
2
2
VCC
GND
GND
GND
DA TA
CKOUT
Part Size Value Tolerance Description
CF1 0603 4.7 nF
CF2 0603 56 pF
CX 0603 100 pF
C1 0603
C2 0603
100 pF
6.8 pF
C3 0603 330 pF
C4 0805 33 nF
L1 0603 270 nH
L2 0603 12 nH
RF1
R1
0603
0603
1 kΩ±10%
See output power
selection table
R2
0603
See output power
selection table
XTAL HC49/S 27.1344 MHz
fundamental wave
±10%
±10%
±10%
±5%
±5%
±10%
±10%
±5%
±5%
±10%
±10%
±30ppm
calibration
±30ppm temp.
loop filter capacitor
loop filter capacitor
XOSC capacitor
impedance matching capacit o r
impedance matching capacit o r
blocking capacitor
blocking capacitor
impedance matching inductor
impedance matching inductor
loop filter resistor
ASK power-select resistor, not requirement at CW mode
ASK or CW mode power-select resistor
crystal, C
R
m, max
= 12 pF to 15 pF, C
load
= 40 Ω
0, max
= 7 pF,
TH71082 Data Sheet Page 7 of 10 Dec. 2001
3901071082 Rev. 004
Page 8
Package Information
123
D
TH71082
868/915MHz
ASK Transmitter / LO Source
E1 E
A1 A
e
all Dimension in mm, coplanarity < 0.1mm
min 4.80 3.81 5.80 1.32 0.10 1.27 0.36 0.41 0°
max 4.98 3.99 6.20 1.72 0.25 0.46 1.27 8°
all Dimension in inch, coplanarity < 0.004”
min 0.189 0.150 0.2284 0.060 0.0040 0.05 0.014 0.016 0°
max 0.196 0.157 0.2440 0.068 0.0098 0.018 0.050 8°
b
Fig. 6: SOIC8 (Small Outline Package)
D E1 E A A1 e b L
L
α
αααα
TH71082 Data Sheet Page 8 of 10 Dec. 2001
3901071082 Rev. 004
Page 9
Your Notes
TH71082
868/915MHz
ASK Transmitter / LO Source
TH71082 Data Sheet Page 9 of 10 Dec. 2001
3901071082 Rev. 004
Page 10
Your Notes
TH71082
868/915MHz
ASK Transmitter / LO Source
Important Notice
Devices sold by Mele xis are covered by th e warranty and pate nt indemnification pr ovisions appearing in i ts Term of S ale. Melexis makes no warrant y,
express, statutory, implied, or by description regarding the informatio n set forth herein or re garding the freedom of the described devices from patent
infringement. Melexis res erves the ri ght to cha nge sp ecific ations and p rices at any time and without notice . The refore, p rio r to designing this product into a
system, it is necessary t o check with Melexis for curr ent information. This product is intended for use in norm al commercial applications. Applications
requiring extended temperature range, unusual environmental requirements, or high reli ability applications, such as military, medical life-support or lifesustaining equipment are specifically not recommended without additional processing by Melexis for each application.
The information furnis hed by Melexis is believed to be cor rect and accurate. How ever, Melexis shall not be liable to recipi ent or any third party for any
damages, including b ut not limited to personal injury, pro perty damage, loss of p rofits, loss of use , interrupt of business or indirect, speci al incidental or
consequential dama ges, of any kind, in connection wit h or arising out of the fu rnishing, per formance or u se of the techni cal data herei n. No obligati on or
liability to recipient or any third party shall arise or flow out of Melexis’ rendering of technical or other services.
© 2000 Melexis NV. All rights reserved.
For the latest version of this document. Go to our website at
www.melexis.com
Or for additional information contact Melexis Direct:
Europe and Japan: All other locations:
Phone: +32 1361 1631 Phone: +1 603 223 2362
QS9000, VDA6.1 and ISO14001 Cer tif ied
TH71082 Data Sheet Page 10 of 10 Dec. 2001
3901071082 Rev. 004
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