TDA5150 Datasheet, PDF (45/106 Pages) Infineon Technologies AG – On-chip, high resolution fractional-N synthesizer and Sigma-Delta modulator with ASK, FSK, GFSK options

TDA 5150
TDA 5150 Functional Description
2.4.8 Power Amplifier, ASK Modulator
The RF signal, generated by VCO and under the control of the Sigma-Delta fractional-
N PLL is fed to a group of class-C Power Amplifier stages, before being transmitted. The
Power Amplifier (PA) includes an output power control, ASK sloping, switchable
capacitors for antenna fine tuning and an auto switch -off mechanism, as part of the Fail-
Safe system. If critical supply voltage or frequency error events occur, the Fail-Safe
mechanism switches off the PA, thus preventing erroneous transmissions...
from SDPLL
ASK
sloping
TDA 5150
PA
matching
network
(external)
ASK-data
Figure 16 Transmitter Blocks
In FSK or GFSK mode, the PA is always ON during the transmission’s duration.
By ASK mode, the SDPLL delivers a continuous RF signal to the PA. The PA is switched
ON and OFF, according the data signal to be transmitted. Additionally there is an ASK
sloping mechanism, which switches the different power stages ON (and OFF) in a well
determined sequence, correlated with the transitions on data signal line. This power
ramping procedure minimizes out-of band transients and spectral splatter.
2.4.8.1 PA Output Power Programming
The PA comprises 11 elementary cells in parallel. Each one is a class-C amplifier.
The cells are grouped in three PA blocks.
PA Block 0 is composed of 9 stages, PA Block 1 and PA Block 2 are strong single stages.
Each PA Block can be individually enabled and disabled to optimize power consumption
and efficiency in an output power subrange. The overall 11 PA stages allow control of
the RF output power in 11 steps over a range of 20 dB. The PA can be switched OFF
by disabling all the 11 stages.
Data Sheet
45
V 1.0, July 2009