TRF372017_16 Datasheet, PDF (48/60 Pages) Texas Instruments – Integrated IQ Modulator PLL/VCO

TRF372017
SLWS224E – AUGUST 2010 – REVISED JANUARY 2016
+5 V
www.ti.com
115
634
DAC3283
+5 V
GND
115
634
68 nH
2.2 pF
DNI
2.7 pF
68 nH
1 mF
60.4
10 nH
90.9
10 nH
1 mF
60.4
TRF3720
GND
Figure 87. DAC to TRF372017 Interface With Internal VCM Generation
8.2.2.3 LO Outputs
The LO outputs are open collector outputs. They require a pullup to V_CC. 75-Ω pullup resistors to V_CC with local
decoupling provides a good broadband match and is shown in an example circuit in Figure 88. An inductor pullup
in parallel with a cap can provide a tuned load for excellent narrowband load matching.
+3.3 V
LO_OUT_P
LO_OUT_N
75
75
47 pF
47 pF
Figure 88. Example LO_OUT Circuit for Broadband Operation
8.2.2.4 Loop Filter
Loop filter design is critical for achieving low closed loop phase noise. Some typical loop filter component values
are given in Table 30, referenced to designators in Figure 89. These loop filters are designed using charge pump
current of 1.94 mA to minimize noise.
f_PFD (MHz)
40
1.6
6.4
10
30.72
C1 (pF)
1000
47
100
270
2200
Table 30. Typical Loop Filter Components
C2 (pF)
10000
560
1000
4700
20000
R2 (kΩ)
0.47
10
5
1.5
0.47
C3 (pF)
39
4.7
20
4700
220
R3 (kΩ)
1.4
5
5
1.5
0.475
C4 (pF)
1.8
open
open
open
220
R4 (kΩ)
3.3
0
0
0
0.475
48
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