MAX1473_1 Datasheet, PDF (3/6 Pages) Maxim Integrated Products – Evaluation Kit

MAX1473 Evaluation Kit
Additional Evaluation
1) With the modulation still set to AM, observe the
effect of reducing the RF generator’s amplitude on
the DATA_OUT terminal output. The error in this
sliced digital signal increases with reduced RF sig-
nal level. The sensitivity is usually defined as the
point at which the error in interpreting the data (by
the following embedded circuitry) increases beyond
a set limit (BER test).
2) With the above settings, a 315MHz-tuned EV kit
should display a sensitivity of about -117dBm (0.2%
BER) while a 433.92MHz kit displays a sensitivity of
about -115dBm (0.2% BER). Note: The above sensi-
tivity values are given in terms of average peak
power is 3dB higher.
3) Capacitors C5 and C6 are used to set the corner fre-
quency of the 2nd-order lowpass Sallen-Key data fil-
ter. The current values were selected for bit rates up
to 5kbps. Adjusting these values accommodates
higher data rates (refer to the MAX1473 data sheet
for more details).
Layout Issues
A properly designed PC board is an essential part of
any RF/microwave circuit. On high-frequency inputs
and outputs, use controlled-impedance lines and keep
them as short as possible to minimize losses and radia-
tion. At high frequencies, trace lengths that are on the
order of λ/10 or longer can act as antennas.
Keeping the traces short also reduces parasitic induc-
tance. Generally, 1in of a PC board trace adds about
20nH of parasitic inductance. The parasitic inductance
can have a dramatic effect on the effective inductance.
For example, a 0.5in trace connecting a 100nH inductor
adds an extra 10nH of inductance or 10%.
To reduce the parasitic inductance, use wider traces
and a solid ground or power plane below the signal
traces. Also, use low-inductance connections to ground
on all GND pins, and place decoupling capacitors
close to all VDD connections.
The EV kit PC board can serve as a reference design
for laying out a board using the MAX1473. All required
components have been enclosed in a 1.25in ✕ 1.25in
square, which can be directly “inserted” into the appli-
cation circuit.
Detailed Description
Power-Down Control
The MAX1473 can be controlled externally using the
SHDN connector. The IC draws approximately 1.25µA
in shutdown mode. Jumper JU1 is used to control this
mode. The shunt can be placed between pins 2 and 3
for continuous shutdown, or pins 1 and 2 for continuous
operation. Remove the JU1 shunt for external control.
Table 1 describes jumper functions.
Power Supply
The MAX1473 can operate from 3.3V or 5V supplies.
For 5V operation, remove JU7 before connecting the
supply to VDD. For 3.3V operation, connect JU7.
IF Input/Output
The 10.7MHz IF can be monitored with the help of a
spectrum analyzer using the MIX_OUT SMA connector
(not provided). Remove the ceramic filter for such a
measurement and include R3 (270Ω) and C17 (0.01µF)
to match the 330Ω mixer output with the 50Ω spectrum
analyzer. Jumper JU3 needs to connect pins 1 and 2. It
is also possible to use the MIX_OUT SMA connector to
inject an external IF as a means of evaluating the base-
band data slicing section. Jumper JU3 needs to con-
nect pins 2 and 3.
F_IN External Frequency Input
For applications where the correct frequency crystal is
not available, it is possible to directly inject an external
frequency through the F_IN SMA connector (not provid-
ed). Connect the SMA connector to a function genera-
tor. The addition of C18 and C19 is necessary (use
0.01µF capacitors).
AGC Control
Jumper JU5 controls whether the AGC is enabled.
Connect pins 2 and 3 to enable the AGC.
Crystal Select
Jumper JU2 controls the crystal divide ratio.
Connecting pins 1 and 2 sets the divide ratio to 64,
while connecting pins 2 and 3 sets the ratio to 32. This
determines the frequency of the crystal to be used.
Image Rejection Frequency Select
A unique feature of the MAX1473 is its ability to vary at
which frequency the image rejection is optimized. JU6
allows the selection of three possible frequencies:
315MHz, 375MHz, and 433.92MHz. See Table 1 for set-
tings.
Test Points and I/O Connections
Additional test points and I/O connectors are provided
to monitor the various baseband signals and for exter-
nal connections. See Tables 2 and 3 for a description.
For additional information and a list of application
notes, consult the www.maxim-ic.com website.
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