ML7406 Family LSIs Hardware Design Manual
FEXL7406DG-01
9
4.2. Note on the VCO tank circuit
Note the following when designing the VCO tank circuit.
1.
In order to stable VCO oscillation, the VCO tank components (L1 and C1) should be placed as close to the
IND1 (#28) and IND2 (#30) pins as possible, recommends within 2 mm. Since the line inductance and
capacitance of PCB will effect to the oscillation frequency.
2.
ML7406 maximum output power is more than 20mW. As shown in the Figure 4.2.1, high output will flow
on the transmission path from PA_OUT (#20) pin. If this output affects on VCO tank circuit, it may cause
the PLL unlock. In Rx, signal radiated from VCO tank, may affect receiving characteristics.
So be careful the followings:
2.1.
VCO tank inductor L1 and PA choke inductor L3 or LNA matching inductor L2 should be placed so that
their positional relationship becomes the 90 degrees to avoid their coupling (Refer to Figure 4.2.2).
2.2.
L1 and L3 or L2 should be placed close to their connect pins of ML7406. They should not be placed
close to each other..
2.3.
RF maching circuit should not be close to the L1.
Figure 4.2.1 Notes on the VCO tank circuit
IND1 (#28)
REG_PA (#21)
PA_OUT (#20)
PA
Regulator
VCO
Matching
Network
PA
L3
20mW
Interference signal
IND2 (#30)
L1
C1
LNA_P (#24)
LNA
Matching
Network
ANT
_SW
L2