MAX9985ETX Maxim Integrated Products, MAX9985ETX Datasheet - Page 13

• Manufacturer Part Number: MAX9985ETX
• Description: Up-Down Converters Dual, SiGe, High-Lin earity, 700MHz to 10
• Manufacturer: Maxim Integrated Products

Specifications of MAX9985ETX

• Maximum Input Frequency: 1000 MHz
• Maximum Power Dissipation: 10800 mW
• Maximum Operating Frequency: 250 MHz
• Maximum Power Gain: 7.5 dB
• Operating Supply Voltage: 5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: TQFN-36 EP

Bias currents for the two on-chip LO buffers is opti-
mized by fine-tuning the off-chip resistors on LODBIAS
(pin 17) and LOMBIAS (pin 29). The current in the
buffer amplifiers is reduced by increasing the value of
these resistors, but performance may degrade. See the
Typical Operating Characteristics for key performance
parameters versus this resistor value. Doubling the
value of these resistors reduces the total chip current
by approximately 50mA (see Table 1).
Bias currents for the two on-chip IF amplifiers are opti-
mized by fine-tuning the off-chip resistors on IFDBIAS
(pin 11) and IFMBIAS (pin 35). The current in the IF
amplifiers is decreased by raising the value of these
resistors, but performance may degrade. See the
Typical Operating Characteristics for key performance
parameters versus this resistor value. Doubling the
value of this resistor reduces the current in each IF
amplifier from 100mA to approximately 50mA (see
Table 1).
Short LEXT_ to ground using a 0Ω resistor. For applica-
tions requiring improved RF-to-IF and LO-to-IF isolation,
LEXT_ can be used by connecting a low-ESR inductor
from LEXT_ to GND. See the Typical Operating
Characteristics on RF-to-IF port isolation and LO-to-IF
port leakage for various inductor values. The load
impedance presented to the mixer must be such that
any capacitance from both IF- and IF+ to ground do not
exceed several picofarads to ensure stable operating
conditions.
Approximately 100mA flows through LEXT_, so it is
important to use a low-DCR wire-wound inductor.
A properly designed PCB is an essential part of any
RF/microwave circuit. Keep RF signal lines as short as
possible to reduce losses, radiation, and inductance.
For the best performance, route the ground pin traces
directly to the exposed paddle under the package. The
PCB exposed paddle MUST be connected to the
ground plane of the PCB. It is suggested that multiple
vias be used to connect this paddle to the lower-level
ground planes. This method provides a good RF/ther-
mal-conduction path for the device. Solder the exposed
paddle on the bottom of the device package to the
PCB. Refer to the MAX9985 Evaluation Kit as a refer-
ence for board layout. Gerber files are available upon
request at www.maxim-ic.com.
Dual, SiGe, High-Linearity, 700MHz to 1000MHz
Downconversion Mixer with LO Buffer/Switch
______________________________________________________________________________________
IF Amplifier Bias Resistors
LO Buffer Bias Resistors
Layout Considerations
LEXT Inductor
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass each V
TAPMAIN/TAPDIV with the capacitors shown in the
Typical Application Circuit (see Table 2 for component
values). Place the TAPMAIN/TAPDIV bypass capacitor
to ground within 100 mils of the pin.
The exposed paddle (EP) of the MAX9985’s 36-pin thin
QFN-EP package provides a low thermal-resistance
path to the die. It is important that the PCB on which the
MAX9985 is mounted be designed to conduct heat
from the EP. In addition, provide the EP with a low-
inductance path to electrical ground. The EP MUST be
soldered to a ground plane on the PCB, either directly
or through an array of plated via holes.
Table 2. Component Values
C10, C11, C12,
C1, C2, C7, C8
C19, C20, C21
COMPONENT
C9, C13, C15,
L1, L2, L4, L5
C17, C18
C14, C16
C3, C6
C4, C5
R1, R4
R2, R5
R3, R6
L3, L6
T1, T2
U1
0.033µF
Exposed Paddle RF/Thermal
VALUE
1.07kΩ
0.01µF
560nH
150pF
1.1kΩ
30nH
39pF
82pF
0Ω
4:1
—
—
Power-Supply Bypassing
Microwave capacitors (0402)
Microwave capacitors (0603)
Not used
Microwave capacitors (0402)
Microwave capacitors (0603)
Microwave capacitors (0402)
Wire-wound high-Q inductors
(0805)
Wire-wound high-Q inductors
(0603)
±1% resistors (0402)
±1% resistors (0402)
Resistors (1206)
Transformers (200:50)
Mini-Circuits TC4-1W-7A
MAX9985 IC
DESCRIPTION
Considerations
CC
pin and
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