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AS3902 ISM 433 MHz ASK Transmitter
Preliminary Data Sheet Rev. A7, December 2000
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
Key Features
* 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 (" ), 1 mA @ transmitting a Low (" ). H" L" * Wide operating temperature range from -40 C to +85 C.
* Miniature surface mount 8 pin MSOP (preferred) or SOIC package.
General Description
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 management (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.
Applications
* Short range radio data transmission. * Remote keyless entry systems. * Domestic and consumer remote control units. * Cordless alarm systems. * Remote metering. * Low power telemetry.
Rev. A7, December 2000
Page 2 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
NRES/PD TXD XTAL CLK/NWUP
1 2 3 4
8
VDD ANT1 ANT2 GND
AS3902
7 6 5
MSOP-8 (or SOIC-8)
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
Functional Description
The AS3902 consists of a reference XTAL oscillator, a single channel RF- synthesizer, a driving amplifier and a C interface, including microprocessor clock divider and a sophisticated power up/down circuitry.
GND
Synthesizer Divider 1/32 Driving Amplifier. VCO LoopFilter Phase detector Clock on/off on/off XTAL Oscillator
CLK/NWUP
5
ANT2 VDD f =433.920 MHz
4
XTAL
6
ANT1
3
TXD
13.560 MHz XTAL
7
VDD
2
NRES/PD
8
C Interface + Power up/down
1
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, generating the 433 MHz transmit carrier frequency fRF by a fix, 32 times, multiplication of the reference XTAL frequency fXTAL.
1.2 Microprocessor Clock
The microprocessor clock frequency fCLK is generated by dividing the XTAL frequency fXTAL by 4.
Rev. A7, December 2000
Page 3 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
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 = " means a turned on state. H" When TXD = " , at first the synthesizer is turned on. The following turning on of the driving H" amplifier is internally delayed for tDRON 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 " , both, L" 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 mArms. The maximal differential voltage swing is about 4 VPP (1.4 VRMS). Therefore the output power is a function of the connected load impedance. With a 2 k differential load a nominal output power (to the antenna) of mW is obtained. Please note that the finally radiated 1 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 " C reset output/transmitter power down input" (NRES/PD). L" " clock output/active " wake-up input" (CLK/NWUP). C L" 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.
AS3902
TXD
I O
uC
P1 SERIAL DATA OUT P2 END TRANSMIT NRESET CLOCK
10k NRES/PD I/O CLK/NWUP I/O 10k SW Transmit switch
Figure 2:
Note:
O I I
Interconnection of the AS3902 with a typical C.
At room temperature, resistor values of k are suggested for the C interface. 10 For other temperatures to be calculated from figure 6.
Rev. A7, December 2000
Page 4 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
open
SW
closed
CLK/NWUP NRES/PD P2 standby startup 32 clocks 16 clocks transmit 4 clocks standby
Figure 3:
Note:
C interface timing for a transmission cycle.
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 " or " by the internal pull-up device or by the C via a resistor. These weak states can be H" L" 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 VCC-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 " , holding the C in reset state. In standby L" 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 " state) and internally pulled up Z" to " . H" (Re)starting the transmitter: Closing the push button (giving a falling edge on CLK/NWUPCLOCK 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 " for 16 clock H" cycles. The transmitter is now in active mode. The NRES/PD acts in AS3902 active mode as an input waiting for a " to trigger the transmission of the transmitter to standby mode. L" 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 " and pulls the NRES/PDL" NRESET line to " . Sensing this, 4 clock cycles later the AS3902 will switch back to standby L" mode, disabling the CLK/NWUP output, setting the active NRES/PD pin to " and turning off L" the XTAL oscillator. Repetitive transmission: If the button is still pressed when the C indicates " end of transmission" by setting P2 pin to " and pulling the NRES/PD-NRESET line to " , 4 C clock periods L" L" 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.
Rev. A7, December 2000
Page 5 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
2
Electrical Characteristics
2.1 Absolute Maximum Ratings (non operating)
Symbol VDD GND VIN ESD TSTG TLEAD
Note: 1) 2)
Parameter Positive supply voltage Negative supply voltage Voltage on input pins Electrostatic discharge Storage temperature Lead temperature
Min -0.5 0 -0.5
Max 7 0 VDD+0.5 1000
Units V V V V C C
Note
1)
-55
125 260
2)
HBM: R = 1.5 k , C = 100 pF. The pins ANT1, ANT2 and XTAL have 500 V ESD protection. 260 C for 10 s (reflow and wave soldering), 360 C for 3 s (manual soldering).
2.2 Operating Conditions
Symbol VDD GND IDD IDD IDD(off) TAMB
Note: 1) 2)
Parameter Positive supply voltage Negative supply voltage Supply current in active mode transmitted " (TXD=" ). L" L" Supply current in active mode, transmitted " (TXD=" ). H" H" Supply current in standby mode Ambient temperature range
Min 2.7 0
Typ 3.0 0 1 7.7
Max 5.0 0 1500 9 1
Unit V V A mA A C
Note
1) 2)
-40
+85
T AMB =23 C, Synthesizer and driving amplifier are turned off, for worst case process and maximum supply voltage: 5mA T AMB =23 C, Synthesizer and driving amplifier are turned on, for worst case process and maximum supply voltage: 12mA
Rev. A7, December 2000
Page 6 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
2.3 ASK Operation
TAMB = 23 C, VDD = 3.0 V, unless specified otherwise.
Symbol fRF POUT,H POUT,L POUT 3rd PSP fCLK tSWM tSTUP tDRON RASK tr,f
Note: 1) 2) 3) 4)
Parameter Transmit frequency (Europe) Available output power Leakage output power Radiated third harmonic output power Spurious power C clock frequency Minimum switch close time Start up time Driving amplifier turn on delay ASK data rate range Carrier rise / fall time
Conditions fXTAL = 13.560 MHz In 2 k , TXD = " H" In 2 k , TXD = " L" Antenna attenuation > 20 dB In distance of fCLK or fXTAL from carrier.
Min
Typ 433,920 0 -inf. -30 -25 3.390 1
Max
Units MHz dBm
Note 1) 2)
-80
dBm dBC dBC MHz ms ms s 3)
Until clock output
2 21
For a RF packet duty cycle 45 %.
0 8
32
kb/s s
4)
XTAL tolerances will slightly change the typical transmit frequency. Output power depends on load impedance, differential output current is typical 0.7 mArms. Maximum differential voltage swing is typical 4 VPP (1.4 VRMS). Actual E.I.R.P. depends on antenna efficiency. 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). Guaranteed, higher data rates possible.
Rev. A7, December 2000
Page 7 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
2.4 Digital Pin Characteristics
TAMB = 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 VOL tr td jcc VIH VIL IIH IIL High level output voltage IOH =-1 mA Low level output voltage IOL =1 mA Rise time Fall time Cycle to cycle jitter High level input voltage Low level input voltage High level input current Low level input current VIH = VDD VIL =0 V; Due to internal pull-up -17 VDD-0.5 0.3 1 CLoad = 10 pF CLoad = 10 pF VDD-0.5 20 20 +/-5 0.6 V V ns ns % V V A A 2) 1)
TX (serial data input) VIH VIL IIH IIL High level input voltage Low level input voltage High level input current Low level input current VIH= VDD; Due to internal pull-down VIL =0 V -1 VDD-0.5 0.3 35 V V A A
NRES/PD (C reset output / transmitter power down input) VOH VOL VIH VIL IIH IIL High level output voltage IOH = -1mA Low level output voltage IOL = 1mA High level input voltage Low level input voltage High level input current Low level input current VIH = VDD VIL =0 V; Due to internal pull-up -17 VDD-0.5 VDD-0.5 0.3 1 0.6 V V V V A A 2)
Note: 1) 2)
guaranteed by design cf. Figure 6
Rev. A7, December 2000
Page 8 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
3
1 2 3 4 5 6 7 8
Pin-out Information
Pin Name NRES/PD TXD XTAL CLK/NWUP GND ANT2 ANT1 VDD Input / Output Dig. tri-state I/O, pull up during active cycle Dig. Input with pull down Analog I/O Dig. tri-state I/O with pull up Power Analog open collector output Analog open collector output Power Description C reset output/transmitter power down input Transmit data input XTAL pin C clock output/wake-up input (push button) Ground To loop antenna To loop antenna Positive supply
Pin #
4
Application Schematic
/PD /NWUP
AS3902
Figure 5:
Basic application schematic of the AS3902.
Rev. A7, December 2000
Page 9 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
Figure 6:
Pull up characteristics for the CLK/NWUP and NRES/PD pin.
Rev. A7, December 2000
Page 10 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
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.
Rev. A7, December 2000
Page 11 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
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.
Rev. A7, December 2000
Page 12 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
Figure 10:
Spurious emissions of the AS3902 measured close to the ETSI EN 300 220-1 recommendation for wide-band equipment, clause 8.7, without modulation, transmitting a constant " . (Only difference: 100 kHz RBW was used instead of 120 kHz). The highest H" 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 reception.
Figure 11:
Demodulated RF wave for 10101... data pattern at 32kbit/s (linear scale)
Rev. A7, December 2000
Page 13 of 14
ISM 433 MHz ASK Transmitter - Preliminary Data Sheet AS3902
6
Package Information
Figure 12:
Physical package dimensions.
Symbol
8 pin SOIC Dimensions Minimal (mm/mil) Nominal (mm/mil) Maximal (mm/mil) 1.75/0.069 0.25/0.010 0.51/0.020 1.27/0.050 5.80/0.228 3.80/0.150 0.40/0.016 0 6.20/0.244 4.00/0.157 1.27/0.050 8 5.00/0.197
8 pin MSOP Dimensions Minimal (mm/mil) 0.94/0.037 0.05/0.002 0.32/0.0125 2.90/0.114 Nominal (mm/mil) 1.01/0.04 0.10/0.004 0.33/0.0130 3.00/0.118 0.65/0.0256 BSC 4.75/0.187 2.90/0.114 0.53/0.0209 0 4.90/0.193 0.30/0.118 0.55/0.0215 3 5.05/0.199 3.10/0.122 0.56/0.0221 6 Maximal (mm/mil) 1.09/0.043 0.15/0.006 0.34/0.0135 3.10/0.122
A A1 b D e E E1 L
1.35/0.053 0.10/0.004 0.33/0.013 4.80/0.189
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 (c) 2000, Austria Mikro Systeme International AG, Schlo Premstatten, 8141 Unterpremstatten, 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.
Rev. A7, December 2000
Page 14 of 14

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