MAX2690EUB 查看數據表（PDF） - Maxim Integrated
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MAX2690EUB Datasheet PDF : 10 Pages
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Low-Noise, 2.5GHz
Downconverter Mixer
______________________________________________________________Pin Description
PIN NAME
FUNCTION
Inductive Degeneration Pin. For maximum linearity, connect LGND directly to ground with no series induc-
1
LGND tance. Trade off linearity for gain by increasing the series inductance from LGND to ground. See the
Applications Information section for more information.
2
GND
RF Ground. This pin must have a separate via to the ground plane, as close to the pin as possible to
minimize inductance.
3
RFIN
RF Input Port. RF Input of Downconverter Mixer. See the Applications Information section for details on
matching to RFIN.
4
RFBYP RF Bypassing Capacitor Pin. Bypass RFBYP with an appropriate-value capacitor (typically 1000pF) to ground.
5
VCC
Supply-Voltage Input, +2.7V to +5.5V. Connect 0.1µF and 1000pF capacitors (in parallel) between VCC
and GND.
6
LO
Local-Oscillator Input. LO should be AC coupled and presents a 50Ω load impedance. See the Applications
Information section for more information.
7
GNDLO
Ground for the LO Port. This pin must have its own via to the ground plane, as close as possible to the pin to
minimize inductance.
Differential IF Inverting Output. IFOUT- is an open-collector output and must be pulled up to VCC with an
8
IFOUT-
external inductor for proper biasing. A resistor in parallel with the inductor may also be used to set a termi-
nating impedance. See the Typical Operating Characteristics section for a plot of IF port characteristics vs.
frequency (see plot titled Single-Ended IF Port Equivalent Shunt RC Network).
Differential IF Noninverting Output. IFOUT+ is an open-collector output and must be pulled up to VCC with
9
IFOUT+
an external inductor for proper biasing. A resistor in parallel with the inductor may also be used to set a ter-
minating impedance. See the Typical Operating Characteristics section for a plot of IF port characteristics
vs. frequency (see plot titled Single-Ended IF Port Equivalent Shunt RC Network).
10
SHDN
Active-Low Shutdown Input. A digital logic-low level at SHDN deactivates all part functions and reduces the
supply current to typically 0.4µA.
_______________Detailed Description
The MAX2690 is a 2.5GHz, double-balanced downcon-
verter mixer designed to provide optimum intermodula-
tion performance for a given supply current. It consists
of a double-balanced Gilbert-cell mixer with single-
ended RF and LO port connections, and a differential
IF port. An on-chip bias cell provides a low-power shut-
down feature.
RF Input
The RFIN and RFBYP pins form the MAX2690’s RF
input. The single-ended RF input signal is applied to
the RFIN pin (refer to the RF Port Impedance vs.
Frequency graph in the Typical Operating Character-
istics). The RFBYP pin should be AC grounded typically
with a 1000pF capacitor. This capacitor value should
present a low impedance at both the RF and IF
frequencies.
IF Output
The IFOUT+ and IFOUT- pins form the MAX2690’s differ-
ential open-collector IF output. The IF output is coupled to
the load using shunt inductors to VCC and series capaci-
tors to the load. Most applications use a resistive termina-
tion of 500Ω (typical) resistors in parallel with the pull-up
inductors to set a terminating impedance. The part’s con-
version gain has been specified with the resistors in place
(using the output network on the MAX2690 EV kit),
accounting for a 3dB loss due to the resistors. Therefore,
it is possible to achieve an increase in gain with a proper-
ly designed matching network. However, the resistors
provide for minimum passband ripple when this port is
connected to typical IF filters.
Bias
The bias cell includes compensation circuitry to mini-
mize conversion-gain variations over temperature as
well as shutdown control circuitry. The SHDN pin can
be used to disable all functions and reduce supply cur-
rent to typically 0.4µA.
_______________________________________________________________________________________ 7
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