TDA5150 Datasheet, PDF (9/106 Pages) Infineon Technologies AG – On-chip, high resolution fractional-N synthesizer and Sigma-Delta modulator with ASK, FSK, GFSK options

TDA 5150
Product Description
1.5.3 Reduction of Spurs and Occupied Bandwidth
The direct FSK modulation and in addition the Gaussian FSK (GFSK) reduces spurs and
occupied bandwidth. Bandwidth reduction is exemplified below
Figure 2
Spectrum of RF-signals with equal frequency deviations (+ 35kHz),
same 20kBit/s datarate and encoding (NRZ). Blue plot corresponds
to FSK modulation and green to GFSK. Observe the difference in
terms of occupied bandwidth between the signals.
1.5.4 Asynchronous and Synchronous Transmission
TDA 5150 offers a simple asynchronous transmission mode (transparent modulation),
whereby after the configuration word is downloaded into the transmitter’s SFRs (via SPI
bus) the data bitstream is output on the SDIO line and fed into the transmitter’s RF
modulator.
The CLKOUT signal can be used either as clock line for host µC or, alternatively, as timer
base (flag) for bitrate generator (this last function should be implemented in µC).
In this mode, the bitrate is solely imposed and controlled by the µC software.
GFSK modulation and ASK shaping options are allowed in Asynchronous Mode.
In Synchronous Transmission Mode the bitrate is solely under the transmitter’s control
and fully timed by the TDA 5150. The CLKOUT is used to alert the µC about the request
for next databit.
The µC may have a higher allowable processing delay tolerance, typically the duration
of 1/2 bit, before sending the corresponding bit via SDIO line to transmitter.
Usage of data encoding option is allowed in Synchronous Mode.
Data Sheet
9
V 1.0, July 2009