AS3902
ISM 433 MHz ASK Transmitter
Preliminary Data Sheet
Rev. A7, December 2000
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 2 of 14
K e y F e a t u r e s
Supports the European 433 MHz ISM band.
No frequency pulling by (antenna) load variation due to PLL synthesizer.
Designed to be conform to EN 300 220-1 requirements.
ASK data rate range from 0 to 32 kbit/s.
Supports clock and reset signals for the external C. Therefore no separate C XTAL is
required.
Supports total shut down mode without any running XTAL oscillator.
Typically 2 external resistors and 3 capacitors required.
FSK operation by XTAL pulling possible.
315 MHz US ISM band application possible.
Wide supply range between 2.7 V to 5 V.
Low TX current, typical 8 mA @ transmitting a High ("H"), 1 mA @ transmitting a Low ("L").
Wide operating temperature range from 40 C to +85 C.
Miniature surface mount 8 pin MSOP (preferred) or SOIC package.
G e n e r a l D e s c r i p t i o n
The AS3902 is a single channel low power 433 MHz ASK transmitter. It uses a fully integrated
PLL stabilized RF-oscillator which avoids frequency pulling by approaching the antenna with
objects as it occurs at SAW resonator based transmitters. ASK modulation is performed by
switching the transmitter on and off by an applied data stream.
The AS3902 contains a bi-directional three line micro-controller (C) interface to support the
C with a clock and a reset signal and to operate the highly efficient power up/down manage-
ment (including clock-free total shut-down) of the AS3902 by the C.
As external components the AS3902 need only a reference XTAL, three capacitors and up to
two resistors.
A p p l i c a t i o n s
Short range radio data transmission.
Remote keyless entry systems.
Domestic and consumer remote control units.
Cordless alarm systems.
Remote metering.
Low power telemetry.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 3 of 14
MSOP-8 (or SOIC-8)
1
2
3
4
NRES/PD
TXD
XTAL
CLK/NWUP
ANT2
GND
ANT1
VDD
8
7
6
5
This document contains information on products under development. Austria Mikro Systeme
International AG reserves the right to change or discontinue this product without notice.
1
F u n c t i o n a l D e s c r i p t i o n
The AS3902 consists of a reference XTAL oscillator, a single channel RF- synthesizer, a driv-
ing amplifier and a C interface, including microprocessor clock divider and a sophisticated
power up/down circuitry.
Driving
Amplifier.
13.560 MHz
XTAL
Loop-
Filter
Synthesizer
XTAL
Oscillator
VCO
on/off
C Interface +
Power up/down
f =433.920 MHz
VDD
ANT1
ANT2
GND
5
6
7
8
VDD
NRES/PD
TXD
XTAL
CLK/NWUP
4
3
2
1
on/off
Clock
Divider
1/32
Phase
detector
Figure 1:
Block diagram of the AS3902.
1.1 RF Synthesizer
The RF synthesizer is a fully integrated single channel device with internal loop filter, generat-
ing the 433 MHz transmit carrier frequency f
RF
by a fix, 32 times, multiplication of the reference
XTAL frequency f
XTAL
.
1.2 Microprocessor Clock
The microprocessor clock frequency f
CLK
is generated by dividing the XTAL frequency f
XTAL
by 4.
AS3902
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 4 of 14
1.3 Modulation
ASK modulation with a data rate from 0 up to 32 kbit/s (for continuous 101010... modulation
pattern) is done by turning the synthesizer and the driving amplifier on and off, whereas a TXD
= "H" means a turned on state.
When TXD = "H", at first the synthesizer is turned on. The following turning on of the driving
amplifier is internally delayed for t
DRON
of 21 s (=72 clock pulses of the C clock) to allow the
synthesizer to lock and settle its frequency prior to transmitting. When TXD becomes "L", both,
synthesizer and driving amplifier are turned off to save power. In this case the synthesizer turn
off is delayed for 21 s.
1.4 Driving Amplifier
The driving amplifier has a differential open collector output optimized for driving of small,
symmetrical high-impedance loop antennas. The amplifier drives a nominal RF current of
0.7 mA
rms
. The maximal differential voltage swing is about 4 V
PP
(1.4 V
RMS
). Therefore the out-
put power is a function of the connected load impedance. With a 2 k
differential load a nomi-
nal output power (to the antenna) of
1 mW is obtained. Please note that the finally radiated
power (from antenna) is lower and strongly dependent on the efficiency (function of the size)
of the antenna to be used.
1.5 C Interface and Power Management
The AS3902 contains a direct interface to a microcontroller (
C). The C interface of the
AS3902 consists of the following three pins:
"Transmit data input" (TXD).
"Active "L" C reset output/transmitter power down input" (NRES/PD).
"C clock output/active "L" wake-up input" (CLK/NWUP).
These lines support the C with the required reset and clock signals and control the AS3902
internal power on/off circuit which wakes up and shuts down the whole transmitter consisting
of the AS3902 and the C.
Figure 2 shows a typical interconnection of the AS3902 with a typical C. Figure 3 presents a
related timing for power up and down of the transmitter.
P1 SERIAL DATA OUT
P2 END TRANSMIT
NRESET
CLOCK
CLK/NWUP
TXD
NRES/PD
10k
uC
10k
Transmit
switch
SW
I
O
O
I/O
I/O
I
I
Figure 2:
Interconnection of the AS3902 with a typical C.
Note:
At room temperature, resistor values of
10 k
are suggested for the C interface.
For other temperatures to be calculated from figure 6.
AS3902
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 5 of 14
SW
CLK/NWUP
NRES/PD
P2
standby
startup
32 clocks
16 clocks
transmit
4 clocks
standby
open
closed
Figure 3:
C interface timing for a transmission cycle.
Note:
The dashed lines indicate weak high or low state when the CLK/NWUP or NRES/PD output of the AS3902 is disabled (in
high-resistive Z state) and pulled "H" or "L" by the internal pull-up device or by the C via a resistor. These weak states can be
overridden by the AS3902 if the respective outputs are enabled. Whenever a line is pulled via an external resistor, however,
this should override the internal pull-up devices of the AS3902.
1.5.1 Interface Description
It is assumed that the
C remains in low power standby mode as long as the P2 pin is kept "L"
and no clock cycles are applied.
Standby: During standby (default after V
CC
-on) the XTAL oscillator is turned off and AS3902
holds the C in a reset state:
The AS3902 NRES/PD pin is active and set to "L", holding the C in reset state. In standby
mode the AS3902 internal NRES/PD pull-up is disabled and does not drain current from the
supply.
The AS3902 CLK/NWUP output is disabled, (in high resistive "Z" state) and internally pulled up
to "H".
(Re)starting the transmitter: Closing the push button (giving a falling edge on CLK/NWUP-
CLOCK line) starts up the AS3902. It turns on its XTAL oscillator and after the oscillator start
up phase it turns the CLK/NWUP pin to active (CMOS level) mode and provides a clock to the
C.
After a delay of 32 C clock cycles the NRES/PD pin of the AS3902 is set to "H" for 16 clock
cycles. The transmitter is now in active mode. The NRES/PD acts in AS3902 active mode as
an input waiting for a "L" to trigger the transmission of the transmitter to standby mode.
During this active mode the C can turn on and off the synthesizer and driving amplifier in the
rhythm of the data on the TX - P1 (Serial data out) line and transmit ASK data.
Bringing the transmitter to standby: After completing the transmission, the C may indicate
"end of transmission" by setting P2 (not end of transmit) to "L" and pulls the NRES/PD-
NRESET line to "L". Sensing this, 4 clock cycles later the AS3902 will switch back to standby
mode, disabling the CLK/NWUP output, setting the active NRES/PD pin to "L" and turning off
the XTAL oscillator.
Repetitive transmission: If the button is still pressed when the C indicates "end of transmis-
sion" by setting P2 pin to "L" and pulling the NRES/PD-NRESET line to "L", 4 C clock periods
later the sequence above will be repeated starting from the 32 clock delay period.
Due to the sophisticated tri-state - active/inactive pull-up configuration of the NRES/PD pin the
AS3902 does not drain current during its standby periods.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 6 of 14
2
E l e c t r i c a l C h a r a c t e r i s t i c s
2.1 Absolute Maximum Ratings (non operating)
Symbol
Parameter
Min
Max
Units
Note
VDD
Positive supply voltage
-0.5
7
V
GND
Negative supply voltage
0
0
V
V
IN
Voltage on input pins
-0.5
VDD+0.5
V
ESD
Electrostatic discharge
1000
V
1)
T
STG
Storage temperature
-55
125
C
T
LEAD
Lead temperature
260
C
2)
Note:
1)
HBM: R = 1.5 k
, C = 100 pF. The pins ANT1, ANT2 and XTAL have 500 V ESD protection.
2)
260 C for 10 s (reflow and wave soldering), 360 C for 3 s (manual soldering).
2.2 Operating Conditions
Symbol
Parameter
Min
Typ
Max
Unit
Note
VDD
Positive supply voltage
2.7
3.0
5.0
V
GND
Negative supply voltage
0
0
0
V
IDD
Supply current in active mode
transmitted "L" (TXD="L").
1
1500
A
1)
IDD
Supply current in active mode,
transmitted "H" (TXD="H").
7.7
9
mA
2)
IDD(off)
Supply current in standby mode
1
A
T
AMB
Ambient temperature range
-40
+85
C
Note:
1)
T
AMB
=23 C, Synthesizer and driving amplifier are turned off, for worst case process and maximum supply voltage: 5mA
2)
T
AMB
=23 C, Synthesizer and driving amplifier are turned on, for worst case process and maximum supply voltage: 12mA
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 7 of 14
2.3 ASK Operation
T
AMB
= 23 C, VDD = 3.0 V, unless specified otherwise.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Note
f
RF
Transmit frequency
(Europe)
f
XTAL
= 13.560 MHz
433,920
MHz
1)
P
OUT
,H
Available output power
In 2 k
, TXD = "H"
0
dB
m
2)
P
OUT
,L
Leakage output power
In 2 k
, TXD = "L"
-inf.
-80
dB
m
P
OUT
3rd
Radiated third harmonic
output power
Antenna attenuation
> 20 dB
-30
dB
C
P
SP
Spurious power
In distance of f
CLK
or
f
XTAL
from carrier.
-25
dB
C
3)
f
CLK
C clock frequency
3.390
MHz
t
SWM
Minimum switch close
time
1
ms
t
STUP
Start up time
Until clock output
2
ms
t
DRON
Driving amplifier turn on
delay
21
s
R
ASK
ASK data rate range
For a RF packet duty
cycle
45 %.
0
32
kb/s
4)
t
r,f
Carrier rise / fall time
8
s
Note:
1)
XTAL tolerances will slightly change the typical transmit frequency.
2)
Output power depends on load impedance, differential output current is typical 0.7 mA
rms
. Maximum differential voltage swing
is typical 4 V
PP
(1.4 V
RMS
).
Actual E.I.R.P. depends on antenna efficiency.
3)
Measurement bandwidth (according to EN 300 220-1) see also figure 10. Actual radiated spurious power depends on antenna
efficentcy and antenna selectivity. Measured with loop antenna (demo board).
4)
Guaranteed, higher data rates possible.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 8 of 14
2.4 Digital Pin Characteristics
T
AMB
= 23 C, VDD = 3.0 V, unless specified otherwise. GND is the 0 V reference.
Input parameters for bi-directional pins (CLK/NWUP, NRES/PD) are valid at disabled outputs.
Symbol Parameter
Conditions
Min
Typ
Max
Units
Note
CLK/NWUP (C clock output / wake-up input)
VOH
High level output voltage IOH =-1 mA
VDD-0.5
-
V
VOL
Low level output voltage IOL =1 mA
-
0.6
V
tr
Rise time
CLoad = 10 pF
20
ns
td
Fall time
CLoad = 10 pF
20
ns
jcc
Cycle to cycle jitter
+/-5
%
1)
VIH
High level input voltage
VDD-0.5
-
V
VIL
Low level input voltage
-
0.3
V
IIH
High level input current
VIH = VDD
1
A
IIL
Low level input current
VIL =0 V; Due to
internal pull-up
-17
A
2)
TX (serial data input)
VIH
High level input voltage
VDD-0.5
-
V
VIL
Low level input voltage
-
0.3
V
IIH
High level input current
VIH= VDD; Due to
internal pull-down
35
A
IIL
Low level input current
VIL =0 V
-1
A
NRES/PD (C reset output / transmitter power down input)
VOH
High level output voltage IOH = -1mA
VDD-0.5
-
V
VOL
Low level output voltage IOL = 1mA
-
0.6
V
VIH
High level input voltage
VDD-0.5
-
V
VIL
Low level input voltage
-
0.3
V
IIH
High level input current
VIH = VDD
1
A
IIL
Low level input current
VIL =0 V; Due to
internal pull-up
-17
A
2)
Note:
1)
guaranteed by design
2)
cf. Figure 6
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 9 of 14
3
P i n - o u t I n f o r m a t i o n
Pin # Pin Name
Input / Output
Description
1
NRES/PD
Dig. tri-state I/O, pull up during
active cycle
C reset output/transmitter power down
input
2
TXD
Dig. Input with pull down
Transmit data input
3
XTAL
Analog I/O
XTAL pin
4
CLK/NWUP
Dig. tri-state I/O with pull up
C clock output/wake-up input (push but-
ton)
5
GND
Power
Ground
6
ANT2
Analog open collector output
To loop antenna
7
ANT1
Analog open collector output
To loop antenna
8
VDD
Power
Positive supply
4
A p p l i c a t i o n S c h e m a t i c
/NWUP
/
PD
Figure 5:
Basic application schematic of the AS3902.
AS3902
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 10 of 14
Figure 6:
Pull up characteristics for the CLK/NWUP and NRES/PD pin.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 11 of 14
5
Typ i c a l M e a s u r e m e n t s
Figure 7:
Narrow band output spectrum of the AS3902 modulated with a 0101-.. data pattern at
16 kbit/s.
Figure 8:
Narrow band output spectrum of the AS3902 modulated with pseudo random data at
16 kbit/s.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 12 of 14
Figure 9:
Modulation bandwidth of the AS3902 at 16 kbit/s, measured close to the ETSI
EN 300 220-1 recommendation for wide-band equipment, clause 8.6. (Only difference:
5 kHz VBW was used instead of 10 kHz). From EN 300 220-1 the modulation bandwidth
is defined to be the frequency difference between the points wherein the power level is
above -36 dBm. Therefore the bandwidth value is dependent on the E.I.R.P. and should
be within the ISM band limits. The marker settings correspond to the limits of the
433 MHz ISM band.
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 13 of 14
Figure 10:
Spurious emissions of the AS3902 measured close to the ETSI EN 300 220-1 recom-
mendation for wide-band equipment, clause 8.7, without modulation, transmitting a con-
stant "H". (Only difference: 100 kHz RBW was used instead of 120 kHz). The highest
spurious emissions are generated at a carrier distance of 3.39 MHz (
C clock frequency).
The EN 300 220-1 specifies an absolute level of -36 dBm E.I.R.P. for spurious emissions.
This limits the maximum E.I.R.P. for a transmitter using the AS3902 to about -11 dBm.
Measurement was performed over a free-space link using R&S HL040 antenna for re-
ception.
Figure 11:
Demodulated RF wave for 10101... data pattern at 32kbit/s (linear scale)
ISM 433 MHz ASK Transmitter Preliminary Data Sheet
AS3902
Rev. A7, December 2000
Page 14 of 14
6
P a c k a g e I n f o r m a t i o n
Figure 12:
Physical package dimensions.
Symbol
8 pin SOIC Dimensions
8 pin MSOP Dimensions
Minimal
(mm/mil)
Nominal
(mm/mil)
Maximal
(mm/mil)
Minimal
(mm/mil)
Nominal
(mm/mil)
Maximal
(mm/mil)
A
1.35/0.053
1.75/0.069
0.94/0.037
1.01/0.04
1.09/0.043
A1
0.10/0.004
0.25/0.010
0.05/0.002
0.10/0.004
0.15/0.006
b
0.33/0.013
0.51/0.020
0.32/0.0125
0.33/0.0130
0.34/0.0135
D
4.80/0.189
-
5.00/0.197
2.90/0.114
3.00/0.118
3.10/0.122
e
1.27/0.050
0.65/0.0256 BSC
E
5.80/0.228
6.20/0.244
4.75/0.187
4.90/0.193
5.05/0.199
E1
3.80/0.150
-
4.00/0.157
2.90/0.114
0.30/0.118
3.10/0.122
L
0.40/0.016
1.27/0.050
0.53/0.0209
0.55/0.0215
0.56/0.0221
0
8
0
3
6
AS's are functional and in-spec circuits which are usually available as samples with documentation and demoboard. However they are
intentionally to be used as a basis for ASIC derivatives. If an AS fits into a customer's application as it is, it will be immediately qualified
and transfered to an ASSP to be ordered as a regular AS product.
Copyright
2000, Austria Mikro Systeme International AG, Schlo Premsttten, 8141 Unterpremsttten, Austria.
Telefon +43-(0)3136-500-0, Telefax +43-(0)3136-52501, E-Mail info@amsint.com
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any
means, without the prior permission in writing by the copyright holder. To the best of its knowledge, Austria Mikro Systeme International
asserts that the information contained in this publication is accurate and correct.
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