Rainbow Electronics MAX2406 - Manual (Page 5)

_______________Detailed Description
The following sections describe each of the blocks in
the MAX2406 Functional Diagram.
The MAX2406 consists of four major components: a low-
noise amplifier (LNA), a downconverter mixer, a local-
oscillator (LO) buffer, and a power-management block.
Low-Noise Amplifier
The LNA is a wideband, single-ended cascode amplifi-
er that can be used over a wide range of frequencies.
Refer to the LNA Gain vs. Frequency graph in the
Typical Operating Characteristics . Its port impedances
are optimized for operation around 1.9GHz, requiring
only a 1pF shunt capacitor at the LNA input for a VSWR
of better than 2:1 at the input and output. As with every
LNA, the input match can be traded off for better noise
figure.
Receive Mixer
The receive mixer is a wideband, double-balanced
design with excellent noise figure and linearity.
RF Inputs
The RXMXIN input is typically connected to the LNA
output through an off-chip filter providing enhanced
flexibility. This input is externally matched to 50
Ω
. See
Figure 1 for an example matching network for 1.9GHz,
and the Rx Mixer Input Impedance vs. Frequency
graph in the
Typical Operating Characteristics .
MAX2406
Low-Cost Downconverter
with Low-Noise Amplifier
_______________________________________________________________________________________ 5
______________________________________________________________Pin Description
NAME FUNCTION
1, 3, 4, 10,
11, 12,
15, 20
GND Ground. Connect to ground plane with minimal inductance.
2 LNAIN
RF Input to the LNA. At 1.9GHz, LNAIN can be easily matched to 50
Ω
with one external shunt 1pF
capacitor. AC couple to this pin. See the LNA Input Impedance vs. Frequency plot in the Typical
Operating Characteristics .
PIN
5, 9 V CC
Supply Voltage (+2.7V to +5.5V). Bypass V CC to GND at each pin with a 47pF capacitor as close to each
pin as possible.
6 RXEN
Enable Control Input, active high. Logic high activates all part functions. A logic low places the device in
shutdown mode.
14 IF
Inverting Side of Downconverter’s Differential Open-Collector IF Output. Follow recommendations for IF
output above. If single-ended operation is desired, connect IF directly to V
CC
.
13 IF
Noninverting Side of Downconverter’s Differential Open-Collector IF Output. Pull IF up to V CC with an
inductor. This inductor can be part of the matching network to the desired IF impedance. Alternatively, a
resistor can be placed in parallel to set a terminating impedance.
8 LO
50
Ω
Inverting Local-Oscillator Input Port. For single-ended LO operation, connect LO directly to GND. If
a differential LO signal is available, AC couple the inverted LO signal to this pin.
7 LO 50 Ω Local-Oscillator Input Port. AC couple to this pin.
19 LNAOUT
LNA Output. This output typically provides a VSWR of better than 2:1 at frequencies from 1.8GHz to 2.5GHz
with no external matching components. At other frequencies, a matching network may be required to match
this pin to an external filter. Consult the LNA Output Impedance vs. Frequency plot in the
Typical Operating
Characteristics .
16 RXMXIN
RF Input of Downconverter Mixer. AC couple to this pin. A matching network may be required to match
RXMXIN to an external filter. Consult the Rx Mixer Input Impedance vs. Frequency plot in the
Typical
Operating Characteristics.
17 GND LNA Output Ground. Connect to ground plane with minimal inductance.
18 GND Downconverter Mixer Input Ground. Connect to ground plane with minimal inductance.