Analog Devices ADRV9001 User Manual page 191

Preliminary Technical Data
If a Tx balun is selected that requires a set of external dc bias chokes, careful planning is required. It is necessary to find the optimum
compromise between the choke physical size, choke dc resistance (RDCR) and the balun low frequency insertion loss. In commercially
available dc bias chokes, resistance decreases as size increases. However, as choke inductance increases, resistance increases. Therefore, it
is undesirable to use physically small chokes with high inductance as they exhibit the greatest resistance. For example, the voltage drop of
a 500 nH, 0603 choke at 100 mA is roughly 50 mV.
Table 84. Sample Wire-Wound DC Bias Choke Resistance vs. Size vs. Inductance
Inductance (nH)
100
200
300
400
500
600
When selecting a dc bias choke inductor, shunting impedance of the choke inductor would need to be high for TX frequency band in
order to minimize its loading to outputs . Therefore, the self resonant frequency of the selected choke inductor must be higher than
intended TX frequency.
C
B
L
Tx1_OUT+/
Tx2_OUT+
Tx1 OR Tx2
OUTPUT STAGE
Tx1_OUT–/
Tx2_OUT–
Figure 170. ADRV9001 RF Transmitter Interface Configuration B
Tx1_OUT+/
Tx2_OUT+
Tx1 OR Tx2
OUTPUT STAGE Tx1_OUT–/
Tx2_OUT–
Figure 171. ADRV9001 RF Transmitter Interface Configuration C
1.8V
C
B
Tx1_OUT+/
Tx2_OUT+
Tx1 OR Tx2
OUTPUT STAGE
Tx1_OUT–/
Tx2_OUT–
Figure 172. ADRV9001 RF Transmitter Interface Configuration D
Resistance (Size: 0603)
0.10
0.15
0.16
0.28
0.45
0.52
Rev. PrA | Page 191 of 253
1.8V
L
C C
C
C
1.8V
1.8V
C
C
1.8V
C
B
L L
C
C
1.8V
1.8V
L L
C C
C
C
1.8V
DRIVER
AMPLIFIER
1.8V
C
C
Resistance (Size: 1206)
0.08
0.10
0.12
0.14
0.15
0.20
UG-1828