MAX1472_1 Datasheet, PDF (3/5 Pages) Maxim Integrated Products – Evaluation Kit

MAX1472 Evaluation Kit
5) Calculate the efficiency. This is done using the fol-
lowing equation:
Efficiency = 10 ^ (Pout / 10) / (V x I)
where I is in mA.
For example, the efficiency is 46.6% for an output of
+11dBm, and a current of 9mA (at 3.0V).
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 induc-
tor 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 MAX1472.
Detailed Description
Enable Control
The MAX1472 can be controlled externally using the
ENABLE connector. The IC draws approximately 1nA
(at room temperature) in shutdown mode. Jumper JU1
is used to control this mode. The shunt can be placed
between pins 1 and 2 for continuous operation.
Remove the JU1 shunt for external control. See Table 1
for jumper function descriptions.
Table 1. Jumper Functions
JUMPER
JU1
JU1
JU2
JU2
JU2
JU3
JU3
JU4
JU4
STATE
1-2
NC
1-2
2-3
NC
1-2
2-3
1-2
NC
FUNCTION
Normal operation
External power-down control
RF carrier-transmit mode
Transmit pulse-train mode
External data transmit
External supply operation
Battery operation
Continuous data generation
Data controlled by SW1
Data Input
The MAX1472 EV kit transmits ASK data with data rates
up to 100kbps. JU2 controls whether the MAX1472
transmits CW (jumper pins 1 and 2 connected), an
external data stream (no jumper), or train pulses gener-
ated by the ICM7555 timer (jumper pins 2 and 3 con-
nected). JU4 controls whether the ICM7555 data is
being generated continuously or at the push of SW1.
REF_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 REF_IN SMA (not provided).
Connect the SMA to a low-phase-noise generator. The
addition of C18 and C19 is necessary (use 0.01µF
capacitors).
Battery Operation
The MAX1472 EV kit can be powered by an external
power supply or by the supplied 3V coin-cell battery.
Set jumper JU3 to connect pins 2 and 3 for battery
operation.
RF Output
The MAX1472 EV kit includes two SMA connectors for RF
output. RFOUT is a standard SMA and is used to connect
the PA output to test equipment. Output is matched to
50Ω. ANTENNA_OUT is a reverse polarity SMA and is
used to connect to a 1/4 wave whip antenna . Note that
resistor R2 (0Ω) needs to be added.
I/O Connections
Table 2 lists all I/O connections.
Table 2. I/O Connectors
SIGNAL
RFOUT
REF_IN
ANTENNA_OUT
VSS
VDD
DATA_IN
ENABLE
DESCRIPTION
RF output
External reference frequency input
Reverse polarity SMA for 1/4 wave
antenna
Ground
3.0V power input
Data input
External power-down control
For additional information and a list of application
notes, consult the Maxim website, www/maxim-ic.com.
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