TRF372017 Datasheet, PDF (50/62 Pages) Texas Instruments – Integrated IQ Modulator PLL/VCO

TRF372017
SLWS224C – AUGUST 2010 – REVISED MAY 2012
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AN DIG VCO Tank
PLL
Divider Buffer ^Buffer
Bias
LODIV
IQ
Offset
BB VCM Gen
VCC
SPI &
EEPROM
VCC
TxDIV
Buffer
Mixer
Mod
Figure 91. Power Supply Distribution
DAC INTERFACING WITH EXTERNAL BASEBAND BIAS VOLTAGE
Common mode voltage on the baseband inputs can be generated either internally or externally. An external
interface should provide 1.7V dc and any necessary filtering. A typical interface to a DAC device is shown in
Figure 92.
+5 V
1mF
125 Ω
68 nH
450 Ω
500 Ω
60.4 Ω
10 nH
DAC3283
+5 V
125 Ω
GND
1mF
2.2 pF
DNI
2.7 pF
90.9 Ω
10 nH
TRF3720
450 Ω
500 Ω
68 nH
60.4 Ω
GND
Figure 92. DAC to TRF372017 Interface With External VCM Generation
INTERNAL BASEBAND BIAS VOLTAGE GENERATION
The TRF372017 has the ability to generate DC voltage levels for its baseband inputs internally. Register settings
in the device allow the user to adjust common mode voltage of the I and Q signals separately. There are three
adjustment factors for the baseband inputs. These are described in Table 1.
50
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