MAX2366 MAXIM [Maxim Integrated Products], MAX2366 Datasheet - Page 20

• Manufacturer Part Number: MAX2366
• Description: Complete Dual-Band Quadrature Transmitters
• Manufacturer: MAXIM [Maxim Integrated Products]

Complete Dual-Band
Quadrature Transmitters
Figure 5. 3-Wire Interface Diagram
The low-band tank (TANKL+, TANKL-) and high-band
tank (TANKH+, TANKH-) are fully differential. The exter-
nal tank components are shown in Figure 6. The fre-
quency of oscillation is determined by the following
equation:
C
C
C
C
and traces
C
quency
C
Internal to the IC, the charge pump will have a leakage
of less than 10nA. This is equivalent to a 300MΩ shunt
resistor. The charge-pump output must see an
extremely high DC resistance of greater than 300MΩ.
This will minimize charge-pump spurs at the compari-
son frequency. Make sure there is no solder flux under
the varactor or loop filter.
The MAX2366/MAX2367/MAX2368 EV kit can be used
as a starting point for layout. For best performance,
take into consideration power-supply issues, as well as
the RF, LO, and IF layout.
20
C
f
OSC
INT
D
VAR
PAR
CENT
C
VAR
= Capacitance of varactor
= External coupling capacitor to the varactor
______________________________________________________________________________________
= Internal capacitance of TANK port
= Equivalent variable tuning capacitance
= Parasitic capacitance due to PC board pads
=
= External capacitor for centering oscillation fre-
=
2
π
2 (C
C
D
(C
D
CLK
INT
×
CS
DI
+ C )
C
C
+
B19 (MSB)
C
C
CENT
t
CS
1
B18
+
Layout Issues
C
IF Tank Design
VAR
+
C
PAR
B0
t
CH
) L
A3
t
CWL
To minimize coupling between different sections of the
IC, the ideal power-supply layout is a star configuration,
which has a large decoupling capacitor at a central
V
each going to a separate V
MAX2367/MAX2368 circuit. At the end of each trace is
a bypass capacitor with impedance to ground less than
1Ω at the frequency of interest. This arrangement pro-
vides local decoupling at each V
one via per bypass capacitor for a low-inductance
ground connection.
The layout of a matching network can be very sensitive
to parasitic circuit elements. To minimize parasitic
inductance, keep all traces short and place compo-
nents as close to the IC as possible. To minimize para-
sitic capacitance, a cutout in the ground plane (and
Figure 6. Tank Port Oscillator
t
CWH
CC
node. The V
C
C
D
D
A1
C
C
C
C
C
CENT
CC
A0 (LSB)
t
ES
traces branch out from this node,
L
Matching Network Layout
t
EW
C
PAR
Power-Supply Layout
CC
t
t
t
t
t
t
CS
CH
CWH
ES
CWL
EW
node in the MAX2366/
> 50ns
> 50ns
> 10ns
> 50ns
CC
> 50ns
> 50ns
C
INT
pin. Use at least
MAX2366
MAX2367
MAX2368
-R
n