MAX2620EVKIT Maxim Integrated Products, MAX2620EVKIT Datasheet - Page 3

• Manufacturer Part Number: MAX2620EVKIT
• Description: RF Modules & Development Tools MAX2620 EVAL KIT MAX2620 EVAL KIT
• Manufacturer: Maxim Integrated Products

Specifications of MAX2620EVKIT

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

out. Use the test port provided on the MAX2620 EV kit
to facilitate measurement by installing a 1000pF capac-
itor at C2 and removing C5. (Remove C2 and install C5
to use the MAX2620 as an oscillator.) When using the
test port, subtract an approximately 586ps electrical
delay from the S11 measurement (this delay can be
compensated for on most modern vector network ana-
lyzers) to account for the delay of the transmission line
from the test port to the MAX2620 TANK pin. The test
port should provide a negative input resistance and
thus return gain when S11 is measured on a vector net-
work analyzer. This return gain provides measurement
data that is outside the unit circle of the Smith chart.
A useful technique is to configure the vector network ana-
lyzer to display 1/S11 for this measurement. The vector
network analyzer displays the information inside the unit
circle of the Smith chart. Most modern vector network
analyzers perform this conversion. Input-impedance data
presented in this format (1/S11) is the complement of the
input impedance, which is the impedance desired to pro-
vide the MAX2620 with feedback to oscillate at a particu-
lar frequency. The Typical Operating Characteristics sec-
tion of the MAX2620 data sheet contains a plot of 1/S11
for specific values of C3 and C4 provided in the
MAX2620 EV kit. Also refer to the Tank Circuit Design
section in the MAX2620 data sheet.
Figure 1. MAX2620 EV Kit Schematic
VCONT
VCC
GND
SMA
JU1
PORT
TEST
R2
1k
SMA
_______________________________________________________________________________________
D1
C15
10 F
25V
J1
50
1.5pF
C17
OPEN
C2
VCC
1.5pF
C6
1pF
1000pF
VCC
C5
VCC
C1
L1
2.7pF
10
1pF
C4
C3
R1
SHDN
10
R3
1
2
3
1
2
3
4
C7
1000pF
VCC1
TANK
FDBK
SHDN
MAX2620 Evaluation Kit
MAX2620
The MAX2620 EV kit uses a low-voltage varactor. With
the coupling capacitor C17 kept small, the oscillator cir-
cuit is less affected by losses in the varactor. However,
keeping C17 small also reduces overall tuning range.
L1 on the MAX2620 is a ceramic coaxial resonator,
which provides the best phase-noise performance. For
cost-sensitive applications, the layout for L1 on the
MAX2620 EV kit is a dual pad that accepts either a
spring coil or a ceramic coaxial resonator. When prop-
erly specified, coaxial resonators provide tight toler-
ance inductance at very high Q for best circuit perfor-
mance. Spring coils, such as Coilcraft mini-spring coils,
provide a good cost/performance compromise for cost-
sensitive applications.
The MAX2620 EV kit can serve as a guide for your
board layout. To minimize the effects of parasitic ele-
ments, which may alter circuit performance, remove the
ground plane around and under the components that
make up the resonant circuit (C3–C6, C17, D1, and L1).
Keep PC board trace lengths as short as possible to
minimize parasitic inductance. Also keep decoupling
capacitors C1, C7, and C9 as close to the MAX2620 as
possible, with direct connection to the ground plane.
_____________Layout Considerations
VCC
U1
VCC2
1000pF
GND
OUT
OUT
C8
8
7
6
5
C9
1000pF
L3
10nH
L4
OPEN
R4
OPEN
1000pF
1.5pF
R5
51
C13
OPEN
C10
C14
C12
1000pF
C11
OPEN
50
50
SMA
SMA
OUT
VCC
OUT
3