Max2406, Low-cost downconverter with low-noise amplifier, Applications information – Rainbow Electronics MAX2406 User Manual

Page 6: Lo inputs, If output port, Power-down control, Extended frequency range

MAX2406

LO Inputs

The LO and LO pins are internally terminated with 50

Ω

resistors. See the

Typical Operating Characteristics

for

a plot of LO Port Return Loss vs. Frequency. AC couple
the local-oscillator signal to these pins. If a single-
ended LO source is used, connect LO to ground.

IF Output Port

The receive mixer output appears on the differential IF
and IF pins. These open-collector outputs each require
an external inductor to V

for DC biasing. This port

typically requires a matching network for coupling to an
external IF filter. For single-ended operation, connect
the unused side (typically IF) to V

, and decouple it to

ground with a 1000pF capacitor. Figure 1 shows exam-
ples of single-ended and differential IF port connec-
tions. Refer to the IF and IF Output Impedance vs.
Frequency plot in the

Typical Operating Characteris-

tics

. At lower IF frequencies, a shunt resistor across the

pull-up inductor (in single-ended applications) or
across IF and IF (in differential applications) can be
used to set the IF impedance.

Power-Down Control

Pulling RXEN low places the MAX2406 in shutdown
mode. Power-down is guaranteed with a control voltage
at or below 0.6V. The device exits shutdown in 0.5µs
typical.

__________Applications Information

Extended Frequency Range

The MAX2406 has been characterized at 1.9GHz for
use in PCS applications; however, it operates over a
much wider frequency range. The LNA gain and noise
figure, as well as receive mixer conversion gain, are
plotted over a wide frequency range in the

Typical

Operating Characteristics

. When operating the device

at frequencies other than those specified in the specifi-
cation table, it may be necessary to design or alter the
matching networks on LNAIN, RXMIXIN, IF, and (if
used) IF. In some cases, the internal broadband output
match on LNAOUT may have to be supplemented by
an external matching circuit. The

Typical Operating

Characteristics

provide port-impedance data vs. fre-

quency for use in designing a matching network. The

Low-Cost Downconverter
with Low-Noise Amplifier

_______________________________________________________________________________________

Figure 1. MAX2406 Typical Operating Circuit

MAX2406

RXMXIN

LNAOUT

LNA OUTPUT

*OPTIONAL

IF OUTPUT
(SINGLE-ENDED)

IF OUTPUT
DIFFERENTIAL

DIFFERENTIAL IF OPERATION

GND

RXEN

LNAIN

LNA INPUT

RECEIVER

ENABLE

LO INPUT

(SINGLE-ENDED)

RECEIVE

MIXER

INPUT

47pF

CHOKE

1, 3, 4, 10,
11, 12, 15,
17, 18, 20

220pF

MATCH

220pF

DIFFERENTIAL LO OPERATION

LO INPUT

DIFFERENTIAL

220pF

1000pF

4.7nH

*1pF

220pF

1pF

MATCH