Detailed Description
The MAX2686/MAX2688 are LNAs designed for GPS L1,
Galileo, and GLONASS applications. The devices feature
an optional power-shutdown control mode to eliminate the
need for an external supply switch. The devices achieve
high gain, ultra-low-noise figure, and excellent linearity.
Input and Output Matching
The devices require an off-chip input matching. Only an
inductor in series with a DC-blocking capacitor is needed
to form the input matching circuit. The Typical Application
Circuit shows the recommended input-matching network.
These values are optimized for the best simultaneous gain,
noise figure, and return loss performance. The value of the
input coupling capacitor affects IIP3. A smaller coupling
capacitor results in lower IIP3. The devices integrate an
on-chip output matching to 50
Ω
at the output, eliminating
the need for external matching components. Tables 1 and
2 list typical device S parameters and K
f
values. Typical
noise parameters are shown in Tables 3 and 4.
Shutdown
The devices include an optional shutdown feature to turn
off the entire chip. The devices are placed in active mode
by default once V
CC
is applied, due to the on-chip pull-
up resistor to V
CC
at the RFOUT bump (shared with the
SHDN input). To shut down the part, apply a logic-low to
the RFOUT bump through an external resistor with an
adequate value, e.g., 25kΩ, in order not to load the RF
output signal during active operation.
MAX2686/MAX2688 GPS/GNSS Low-Noise Ampliers
www.maximintegrated.com
Maxim Integrated
│
5
Bump Description
Bump Conguration
BUMP NAME FUNCTION
A1 V
CC
Supply Voltage. Bypass to ground with a 10pF capacitor as close as possible to the IC.
A2
RFOUT
(SHDN)
RF Output/SHDN Input. RFOUT is internally matched to 50Ω and pulled up to V
CC
through a 1MΩ
resistor. SHDN is shared with the RFOUT bump. The devices are in active mode by default once V
CC
is applied. RFOUT(SHDN) can be pulled to a DC low externally to shut down the IC.
B1 RFIN RF Input. Requires a DC-blocking capacitor and external matching components.
B2 GND Ground. Connect to the PCB ground plane.
WLP
TOP VIEW
MAX2686
MAX2688
RFIN
V
CC
GND
RFOUT (SHDN)
A1 A2
B1 B2
+
