MELEXIS EVB72036-315-ASK-A

EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
Features
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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
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Ordering Information
Part No. (see paragraph 5)
EVB72036-868-FSK-C
EVB72036-915-FSK-C
Note: EVB default population is FSK, ASK modification according to section 3.1.
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Application Examples
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Evaluation Board Example
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
General Description
The TH72036 evaluation board is designed to demonstrate the performance of the transmitter IC for conductive measurements. The power amplifier is matched to 50 Ohms by means of a π-matching network to operate at a resonant frequency of 868 and 915 MHz.
The EVB72036 also features a clock output applicable to drive a microcontroller. The clock frequency can be
selected by an external logic signal.
3901272036 01
Rev. 002
Page 1 of 12
EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
Document Content
1
2
3
Theory of Operation ...................................................................................................3
1.1
General............................................................................................................................. 3
1.2
Block Diagram .................................................................................................................. 3
Functional Description ..............................................................................................3
2.1
Crystal Oscillator .............................................................................................................. 3
2.2
FSK Modulation ................................................................................................................ 4
2.3
Crystal Pulling................................................................................................................... 4
2.4
ASK Modulation................................................................................................................ 5
2.5
Output Power Selection.................................................................................................... 5
2.6
Lock Detection.................................................................................................................. 5
2.7
Low Voltage Detection...................................................................................................... 5
2.8
Mode Control Logic .......................................................................................................... 6
2.9
Clock Output..................................................................................................................... 6
2.10
Timing Diagrams .............................................................................................................. 6
50Ω Connector Board Circuit Diagram.....................................................................7
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3.1
Board Component Values ................................................................................................ 7
3.2
50Ω Connector Board PCB Top View .............................................................................. 8
3.3
Board Connection............................................................................................................. 8
4
Evaluation Board Layout ...........................................................................................9
5
Board Variants............................................................................................................9
6
Package Description ................................................................................................10
7
6.1
Soldering Information ..................................................................................................... 10
6.2
Recommended PCB Footprints ...................................................................................... 10
Disclaimer .................................................................................................................12
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
1 Theory of Operation
1.1 General
As depicted in Fig.1, the TH72036 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 (CP). An internal loop filter determines the dynamic behavior of the PLL and suppresses reference spurious signals. A
Colpitts crystal oscillator (XOSC) is used as the reference oscillator of a phase-locked loop (PLL) synthesizer. The VCO’s output signal feeds the power amplifier (PA). The RF signal power Pout can be adjusted in
four steps from Pout = –11 dBm to +9.5 dBm, either by changing the value of resistor RPS or by varying the
voltage VPS at pin PSEL. The open-collector output (OUT) can be used either to directly drive a loop antenna
or to be matched to a 50Ohm load. Bandgap biasing ensures stable operation of the IC at a power supply
range of 1.95 V to 5.5 V.
1.2 Block Diagram
RPS
R1
ASKDTA
CKDIV
VCC
7
10
PSEL
6
PLL
CKOUT
5
ROI
3
32
2
OUT
antenna
matching
network
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XBUF
CP
FSKSW
8
PA
PFD
XOSC
XTAL
CX2
CX1
div 8
div 32
VCO
1
mode
control
4
ENTX
9
FSKDTA
VEE
Fig. 1:
Block diagram with external components
2 Functional Description
2.1 Crystal Oscillator
A Colpitts crystal oscillator with integrated functional capacitors is used as the reference oscillator for the PLL
synthesizer. The equivalent input capacitance CRO offered by the crystal oscillator input pin ROI is about
18pF. The crystal oscillator is provided with an amplitude control loop in order to have a very stable frequency over the specified supply voltage and temperature range in combination with a short start-up time.
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Rev. 002
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
2.2 FSK Modulation
FSK modulation can be achieved by pulling the
crystal oscillator frequency. A CMOScompatible data stream applied at the pin
FSKDTA digitally modulates the XOSC via an
integrated NMOS switch. Two external pulling
capacitors CX1 and CX2 allow the FSK deviation Δf and the center frequency fc to be adjusted independently. At FSKDTA = 0, CX2 is
connected in parallel to CX1 leading to the lowfrequency component of the FSK spectrum
(fmin); while at FSKDTA = 1, CX2 is deactivated
and the XOSC is set to its high frequency fmax.
An external reference signal can be directly ACcoupled to the reference oscillator input pin
ROI. Then the transmitter is used without a
crystal. Now the reference signal sets the carrier frequency and may also contain the FSK (or
FM) modulation.
Fig. 2:
Crystal pulling circuitry
VCC
ROI
XTAL
FSKSW
CX2
CX1
VEE
FSKDTA
Description
0
fmin= fc - Δf (FSK switch is closed)
1
fmax= fc + Δf (FSK switch is open)
2.3 Crystal Pulling
A crystal is tuned by the manufacturer to the
required oscillation frequency f0 at a given load
capacitance CL and within the specified calibration tolerance. The only way to pull the oscillation frequency is to vary the effective load capacitance CLeff seen by the crystal.
Figure 3 shows the oscillation frequency of a
crystal as a function of the effective load capacitance. This capacitance changes in accordance with the logic level of FSKDTA around
the specified load capacitance. The figure illustrates the relationship between the external
pulling capacitors and the frequency deviation.
It can also be seen that the pulling sensitivity
increases with the reduction of CL. Therefore,
applications with a high frequency deviation
require a low load capacitance. For narrow
band FSK applications, a higher load capacitance could be chosen in order to reduce the
frequency drift caused by the tolerances of the
chip and the external pulling capacitors.
f
XTAL
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L1
f max
C0
C1
CL eff
R1
fc
f min
CX1 CRO
CX1+CRO
Fig. 3:
CL
(CX1+CX2) CRO
CX1+CX2+CRO
CL eff
Crystal pulling characteristic
For ASK applications CX2 can be omitted. Then CX1 has to be adjusted for center frequency.
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
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 applied 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 thermometer-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
&
&
&
&
&
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Fig. 4:
OUT
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 desired 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.
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
2.8
Mode Control Logic
The mode control logic allows two different
modes of operation as listed in the following
table. The mode control pin EN is pulled-down
internally. This guarantees that the whole circuit
is shut down if this pin is left floating.
2.9
EN
Mode
Description
0
TX standby
TX disabled
1
TX active
CKOUT active
TX / CKOUT
enabled
Clock Output
The clock output CKOUT is CMOS-compatible and can be used to drive a microcontroller. The frequency of
the clock can be changed by the clock divider control signal CKDIV, that can be selected according to the
following table. A capacitor at pin CKOUT can be used to control the clock voltage swing and the spurious
emission.
CKDIV
Clock divider ratio
Clock frequency / fc=433.92 MHz
0
4
3.39 MHz
1
16
848 kHz
2.10 Timing Diagrams
After enabling the transmitter by the EN signal, the power amplifier remains inactive for the time ton, the
transmitter start-up time. The crystal oscillator starts oscillation and the PLL locks to the desired output frequency within the time duration ton. After successful PLL lock, the LOCK signal turns on the power amplifier,
and then the RF carrier can be FSK or ASK modulated.
high
EN
low
high
LOCK
low
high
FSKDTA
low
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high
EN
low
high
LOCK
low
high
PSEL
low
RF carrier
t
t
t on
t on
Fig. 5:
Timing diagrams for FSK and ASK modulation
For more detailed information, please refer to the latest TH72036 data sheet revision.
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Rev. 002
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
3 50Ω Connector Board Circuit Diagram
Circuit diagram with 50 Ω matching network
Fig. 6:
3.1
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Board Component Values
Part
Size
CM1
0805
CM2
0805
CM3
0805
LM
0805
LT
0805
CX1_FSK
0805
Value @
868.3 MHz
Value @
915 MHz
Tolerance
1.8 pF
2.2 pF
±5%
impedance matching capacitor
5.6 pF
5.6 pF
±5%
impedance matching capacitor
Description
68 pF
68 pF
±5%
impedance matching capacitor r
12 nH
10 nH
±5%
impedance matching inductor
15 nH
10 nH
±5%
output tank inductor
22 pF
22 pF
±5%
27 pF
27 pF
±5%
XOSC FSK capacitor (Δf = ±20 kHz), note 1
XOSC ASK capacitor, trimmed to fC, note 1
12pF
12 pF
±5%
CX1_ASK
0805
CX2
0805
CCK
0805
15 pF/ 180 pF
±5%
XOSC capacitor (Δf = ±20 kHz), note 1, only for FSK
capacitor to control clock voltage swing (CKDIV 0 / 1)
RPS
0805
NIP
±5%
power-select resistor, see data sheet section 4.6
R1
0805
±5%
ASK jumper (for ASK only), see data sheet sect. 4.7
CB0
1206
0Ω
220 nF
±20%
de-coupling capacitor
CB1
0805
330 pF
±10%
de-coupling capacitor
XTAL
SMD
6x3.5
CK
0805
27.13438 MHz
28.59375 MHz
±30ppm cali., ±30ppm temp
1 nF
fundamental mode crystal,
CL = 12 pF, C0, max = 7 pF, R1 = 40 Ω
±10%
ROI coupling capacitor, only required for
external reference frequency input
Note 1: depends on crystal parameters, other ∆f values can be selected with other CX1, CX2 values
NIP – not in place, may be used optionally
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Rev. 002
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
3.2
50Ω Connector Board PCB Top View
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Board size is 27 mm x 42 mm
3.3
VCC
Board Connection
Power supply (1.95 V to 5.5 V)
CKDIV
FSKD Input for FSK data (CMOS, see section 2.2)
ASKD Input for ASK data (CMOS, see section 2.4)
EN
CKOUT Clock output, (CMOS, see section 2.9)
RO
External reference frequency input
Several ground pins
Mode control pin (see par. 2.8)
3901272036 01
Rev. 002
Clock divider input, (CMOS, see sect. 2.9)
Page 8 of 12
EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
4 Evaluation Board Layout
EVB720X6 _1
Board layout data in Gerber format are available, board size is 27mm x 42mm x 1mm FR4.
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PCB bottom view
PCB top view
5 Board Variants
Type
EVB72005
Frequency/MHz
Modulation
–315
–FSK
–433
–ASK
–868
–FM
according to section 3.1
Board Execution
–A
antenna version
–C
connector version
–915
Note:
3901272036 01
Rev. 002
available EVB setups
Page 9 of 12
EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
6 Package Description
The device TH72016 is RoHS compliant.
D
D2
10
6
L
0.23
exposed pad
E2
E
0.36
0.225x45°
5
1
b
A3
A
The “exposed pad” is not connected
to internal ground,
it should not be connected to the PCB.
A1
Fig. 7:
e
10L QFN 3x3 Dual
all Dimensions in mm
min
max
D
E
D2
E2
A
A1
A3
L
e
b
2.85
3.15
2.85
3.15
2.23
2.48
1.49
1.74
0.80
1.00
0
0.05
0.20
0.3
0.5
0.50
0.18
0.30
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all Dimensions in inch
min 0.112 0.112 0.0878 0.051 0.0315
0
0.0118
0.0071
0.0079
0.0197
max 0.124 0.124 0.0976 0.055 0.0393 0.002
0.0197
0.0118
6.1 Soldering Information
•
6.2
The device TH72036 is qualified for MSL3 with soldering peak temperature 260 deg C
according to JEDEC J-STD-20
Recommended PCB Footprints
e
C PL
X
Y
10
6
Z G
E2 th
1
5
min
max
G
D2th
E2th
X
Y
CPL
e
3.55
3.90
1.9
2.3
3.2
3.6
1.3
1.7
0.25
0.30
0.7
1.0
0.3
0.5
0.5
all Dimensions in inch
solder stop
Fig. 8:
3901272036 01
Rev. 002
Z
min 0.1398 0.0748 0.1260 0.0512 0.0098 0.0276 0.0591
0.0197
max 0.1535 0.0906 0.1417 0.0669 0.0118 0.0394 0.0197
D2 th
solder pad
all Dimensions in mm
PCB land pattern style
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
Your Notes
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EVB Description
June/07
EVB72036
868/915MHz FSK/ASK Transmitter
Evaluation Board Description
7 Disclaimer
1) The information included in this documentation is subject to Melexis intellectual and other property rights.
Reproduction of information is permissible only if the information will not be altered and is accompanied
by all associated conditions, limitations and notices.
2) Any use of the documentation without the prior written consent of Melexis other than the one set forth in
clause 1 is an unfair and deceptive business practice. Melexis is not responsible or liable for such altered
documentation.
3) The information furnished by Melexis in this documentation is provided ’as is’. Except as expressly warranted in any other applicable license agreement, Melexis disclaims all warranties either express, implied, statutory or otherwise including but not limited to the merchantability, fitness for a particular purpose, title and non-infringement with regard to the content of this documentation.
4) Notwithstanding the fact that Melexis endeavors to take care of the concept and content of this documentation, it may include technical or factual inaccuracies or typographical errors. Melexis disclaims any
responsibility in connection herewith.
5) Melexis reserves the right to change the documentation, the specifications and prices at any time and
without notice. Therefore, prior to designing this product into a system, it is necessary to check with Melexis for current information.
6) Melexis shall not be liable to recipient or any third party for any damages, including but not limited to
personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the information in this documentation.
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7) The product described in this documentation is intended for use in normal commercial applications. Applications requiring operation beyond ranges specified in this documentation, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by Melexis for each application.
8) Any supply of products by Melexis will be governed by the Melexis Terms of Sale, published on
www.melexis.com.
© 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, Africa:
Americas:
Asia:
Phone: +32 1367 0495
E-mail: [email protected]
Phone: +1 603 223 2362
E-mail: [email protected]
Phone: +32 1367 0495
E-mail: [email protected]
ISO/TS 16949 and ISO14001 Certified
3901272036 01
Rev. 002
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EVB Description
June/07