Datasheet AS3902 Datasheet (Austria Mikro Systeme International)

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 µC. Therefore no separate µC 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.

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 (µC) interface to support the

µC 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 µC.

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

AS3902

VDD 8

7

ANT1
ANT2

6
5

GND

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 µC interface, including microprocessor clock divider and a sophisticated
power up/down circuitry.

on/off

Synthesizer

Loop-

Filter

Divider
1/32

on/off

Phase
detector

XTAL

Oscillator VCO

Clock

µC Interface +
Power up/down

CLK/NWUP

4

XTAL

3

TXD

2

NRES/PD

1

13.560 MHz
XTAL

VDD

f =433.920 MHz

GND

ANT2

ANT1

VDD

5

Driving

6

Amplifier.

7

8

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 f

XTAL

.

1.2 Microprocessor Clock

The microprocessor clock frequency f
by 4.

Rev. A7, December 2000 Page 3 of 14

is generated by dividing the XTAL frequency f

CLK

XTAL

ISM 433 MHz ASK Transmitter – Preliminary Data Sheet

NRESET

CLOCK

CLK/NWUP

NRES/PD

uC

I

O

O

I/OII

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
= “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

of 21 µs (=72 clock pulses of the µC clock) to allow the

DRON

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 µs.

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
put power is a function of the connected load impedance. With a 2 kΩ differential load a nomi­nal 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.

. The maximal differential voltage swing is about 4 VPP (1.4 V

rms

). Therefore the out-

RMS

1.5 µC Interface and Power Management

The AS3902 contains a direct interface to a microcontroller (µC). The µC interface of the
AS3902 consists of the following three pins:
“Transmit data input“ (TXD).
“Active “L“ µC reset output/transmitter power down input“ (NRES/PD).
“µC clock output/active “L“ wake-up input“ (CLK/NWUP).
These lines support the µC 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 µC.
Figure 2 shows a typical interconnection of the AS3902 with a typical µC. Figure 3 presents a
related timing for power up and down of the transmitter.

AS3902

TXD

10k

I/O

P1 SERIAL DATA OUT

P2 END TRANSMIT

10k

SW

Transmit
switch

Figure 2: Interconnection of the AS3902 with a typical µC.

Note: At room temperature, resistor values of ≈10 kΩ are suggested for the µC interface.

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

SW

CLK/NWUP

NRES/PD

P2

standby

startup

32 clocks

16 clocks

transmit

4 clocks

standby

AS3902

open
closed

Figure 3: µC 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 µC 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 µC 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 µC in a reset state:
The AS3902 NRES/PD pin is active and set to “L“, holding the µC 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/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
µC.
After a delay of 32 µC 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 µC 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 µC may indicate
“end of transmission“ by setting P2 (not end of transmit) to “L“ and pulls the NRES/PD­NRESET 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 µC indicates “end of transmis­sion“ by setting P2 pin to “L“ and pulling the NRES/PD-NRESET line to “L“, 4 µC 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.

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 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

T

LEAD

Note:

1) HBM: R = 1.5 kΩ, 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).

Storage temperature -55 125 °C

Lead temperature 260 °C 2)

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“).
IDD Supply current in active mode,

transmitted “H“ (TXD=“H“).
IDD(off) Supply current in standby mode 1

1 1500 µA 1)

7.7 9 mA 2)

µA

T

AMB

Note:

1) T

2) T

Ambient temperature range -40 +85 °C

=23 °C, Synthesizer and driving amplifier are turned off, for worst case process and maximum supply voltage: 5mA

AMB

=23 °C, Synthesizer and driving amplifier are turned on, for worst case process and maximum supply voltage: 12mA

AMB

Rev. A7, December 2000 Page 6 of 14

ISM 433 MHz ASK Transmitter – Preliminary Data Sheet
AS3902

2.3 ASK Operation

T

= 23 °C, VDD = 3.0 V, unless specified otherwise.

AMB

Symbol Parameter Conditions Min Typ Max Units Note

f

RF

Transmit frequency

f

= 13.560 MHz 433,920 MHz 1)

XTAL

(Europe)

P

,H Available output power

OUT

P

,L Leakage output power

OUT

P

3rd Radiated third harmonic

OUT

output power

P

f

CLK

t

SWM

SP

Spurious power In distance of f

µC clock frequency 3.390 MHz
Minimum switch close

In 2 kΩ, TXD = “H“
In 2 kΩ, TXD = “L“
Antenna attenuation

> 20 dB

or

CLK

f

from carrier.

XTAL

0 dB

-inf. -80 dB

-30 dB

-25 dB

1 ms

2)

m

m

C

3)

C

time

t

STUP

t

DRON

Start up time Until clock output 2 ms
Driving amplifier turn on

21 µs

delay

R

ASK

ASK data rate range For a RF packet duty

0 32 kb/s 4)

cycle ≥45 %.

t

r,f

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

3) Measurement bandwidth (according to EN 300 220-1) see also figure 10. Actual radiated spurious power depends on antenna

4) Guaranteed, higher data rates possible.

Carrier rise / fall time 8 µs

. Maximum differential voltage swing

is typical 4 VPP (1.4 V
efficentcy and antenna selectivity. Measured with loop antenna (demo board).

). Actual E.I.R.P. depends on antenna efficiency.

RMS

rms

Rev. A7, December 2000 Page 7 of 14

ISM 433 MHz ASK Transmitter – Preliminary Data Sheet
AS3902

2.4 Digital Pin Characteristics

T

= 23 °C, VDD = 3.0 V, unless specified otherwise. GND is the 0 V reference.

AMB

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 (µC 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 µA

IIL Low level input current VIL =0 V; Due to

-17 µA 2)

internal pull-up

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

35 µA

internal pull-down

IIL Low level input current VIL =0 V -1 µA

NRES/PD (µC 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 µA

IIL Low level input current VIL =0 V; Due to

-17 µA 2)

internal pull-up

Note:

1) guaranteed by design

2) cf. Figure 6

Rev. A7, December 2000 Page 8 of 14

ISM 433 MHz ASK Transmitter – Preliminary Data Sheet

/

NWUP

/

PD

AS3902

3 Pin-out Information

Pin # Pin Name Input / Output Description

1 NRES/PD Dig. tri-state I/O, pull up during

active cycle
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

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

µC reset output/transmitter power down
input

µC clock output/wake-up input (push but­ton)

4 Application Schematic

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 Typical Measurements

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 recom-

mendation for wide-band equipment, clause 8.7, without modulation, transmitting a con­stant “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 (µC 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 8 pin MSOP Dimensions

Minimal

(mm/mil)

Nominal

(mm/mil)

Maximal

(mm/mil)

Minimal

(mm/mil)

Nominal

(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

α

0° 8° 0° 3° 6°

Maximal

(mm/mil)

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, Schloß Premstätten, 8141 Unterpremstätten, Austria.
Telefon [phone], Telefax [phone], E-Mail [e-mail]
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