ISM 868 MHz, 433 MHz and 315 MHz FSK Transmitter – Preliminary Data Sheet

ASCell3911

Rev. A, February 2000

Page 3 of 13

Austria Mikro Systeme International AG

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 ASCell3911 consists at the RF side of a reference XTAL oscillator, a single channel RF-

synthesizer, an I/Q based direct conversion FSK modulator, a driving amplifier. On the digital

side the pulse interference resistant protocol encoder and a µC interface, including microproc-

essor clock divider and a sophisticated power up/down circuitry are implemented.

PAGND

VDDSTN

f =868.3 MHz

RF-

RF+

VDD

13.5672 MHz

XTAL

GNDSYN

DATA

D_EN

µC CLK

D_CLK

GND

VDD

WAKEUP

RESET/TEST

Driving

Amplifier

Quadrature

Up Converter

Baseband

Filters

Loop-

Filter

Synthesizer

XTAL

Oscillator

VCO

90°

Clock

Sin / Cos

Generator

Protocol

Encoder

µC

Int

erf

ac

e

+

Po

we

r

up

/d

ow

n

Transmit.

Timing

Control

Register

Divider

64:1/32:1/16:1

Phase

Detector

Figure 1:

Block diagram of the ASCell3911.

1.1 RF Synthesizer

Frequency synthesis is performed by a single channel synthesizer, consisting of a phase de-

tector, a charge pump, a voltage-controlled oscillator (VCO), and a feedback divider. The VCO is

working at 315,000 to 868,300 MHz. The feedback divider divides by 16 (315,00 MHz), 32

(433,920 MHz) or 64 (868,300 MHz). The different ISM bands are selected by different XTAL fre-

of the different frequencies is given in Table 1.

CRYSTAL RANGE

19,6875

16

H

L

315,000

13,5600

32

L

L

433,920

13,5672

64

L

H

868,300

not used

H

H

not used

Table 1:

Quartz and RF output frequencies.

ASCell3911