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MAX9985
Dual, SiGe, High-Linearity, 700MHz to 1000MHz
Downconversion Mixer with LO Buffer/Switch
LO Buffer Bias Resistors
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
Power-Supply Bypassing
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass each V CC pin and
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.
Table 2. Component Values
by approximately 50mA (see Table 1).
IF Amplifier Bias Resistors
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).
LEXT Inductor
Short LEXT_ to ground using a 0 ? 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 operat-
ing conditions.
COMPONENT
C1, C2, C7, C8
C3, C6
C4, C5
C9, C13, C15,
C17, C18
C10, C11, C12,
C19, C20, C21
C14, C16
L1, L2, L4, L5
L3, L6
R1, R4
R2, R5
R3, R6
T1, T2
U1
VALUE
39pF
0.033μF
—
0.01μF
150pF
82pF
560nH
30nH
1.07k ?
1.1k ?
0 ?
4:1
—
DESCRIPTION
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
Approximately 100mA flows through LEXT_, so it is
important to use a low-DCR wire-wound inductor.
Layout Considerations
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.
Maxim Integrated
Exposed Paddle RF/Thermal
Considerations
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.
13
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MAX9985EVKIT 制造商:Maxim Integrated Products 功能描述:DUAL SIGE HIGH-LINEARITY 700 - 1 - Rail/Tube
MAX9985EVKIT# 功能描述:射频开发工具 RoHS:否 制造商:Taiyo Yuden 产品:Wireless Modules 类型:Wireless Audio 工具用于评估:WYSAAVDX7 频率: 工作电源电压:3.4 V to 5.5 V
MAX9986AETP+ 功能描述:上下转换器 SiGe 815-1000MHz Downconversion Mixer RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128
MAX9986AETP+T 功能描述:上下转换器 SiGe 815-1000MHz Downconversion Mixer RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128
MAX9986AEVKIT 功能描述:射频开发工具 RoHS:否 制造商:Taiyo Yuden 产品:Wireless Modules 类型:Wireless Audio 工具用于评估:WYSAAVDX7 频率: 工作电源电压:3.4 V to 5.5 V
MAX9986ETP 功能描述:上下转换器 SiGe 815-1000MHz Downconversion Mixer RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128
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