TDA5150 Datasheet, PDF (37/106 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
• PLLINT <6:0> and PLLFRAC <20:0> PLL divider SFRs used to define the desired
RF frequency.
• ISMB<1> MSB of SFR register ISMB<1:0>, for band selection.
• VAC_NXOSC<5:0> always set to 32 decimal or 0x20, number of elapsed system
clocks time (duration) used for VAC counting.
2.4.6.3 Loop Filter Bandwidth
In order to provide a high grade of flexibility by choice of modulation parameters, a PLL
with programable bandwidth have been implemented in the TDA5150.
The damping resistor(s), part of the active Loop Filter in PLL can be selected by means
of a 3 bit control field designated PLLBWTRIM in the SFR register PLLBW (0x25.6:4).
Aiming the minima of RF-energy leaking into the adjacent channel(s) and/or out of band
transmissions, the PLL bandwidth should be set as narrow as possible, but not less then
1.5.. 2 times the chip rate, if FSK or GFSK modulation is used.
For NRZ encoding the chip rate and data- or bit rate are the same. For all other coding
schemes like Manchester or Bi-Phase etc. each bit is represented by two chips.
Therefore the chip rate is the double of the bit rate for all encoding schemes,
implemented in the TDA5150 encoder, excepting NRZ.
The chip rate is not influenced by the fact whether the encoding is done by the on-chip
Data Encoder or is realized externally.
In order to maintain loop stability within the PLL and for optimum performance, following
chargepump settings should be used, correlated with loop filter damping:
Table 2
PLL recommended settings
Loop filter
damping resistor
selection
Chargepump settings
and resulting current
Resulting
nominal
PLL BW
PLLBW TRIM
CPTRIM
CP_current [kHz]
Bit2 Bit1 Bit0 Bit3 Bit2 Bit1 Bit0
[uA]
000* * * *
*
*
0011111
40
410
0101100
32.5
375
0111001
25
335
1000110
17.5
270
1010100
12.5
230
1100010
7.5
175
1110001
5
150
Notes
not recommended
Data Sheet
37
V 1.0, July 2009