MAX7031MATJ50+ Maxim Integrated Products, MAX7031MATJ50+ Datasheet - Page 15

• Manufacturer Part Number: MAX7031MATJ50+
• Description: RF Receiver IC TXRX FSK W/PLL-EP 5MHz, and 433.92MHz
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX7031MATJ50+

• Package / Case: TQFN-32 EP
• Operating Frequency: 433.92 MHz
• Operating Supply Voltage: 2.7 V, 5 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Bypass T/R, ENABLE, DATA, AGC0-1, and AUTOCAL
with 10pF capacitors to GND. Place all bypass capaci-
tors as close to the respective pins as possible.
The MAX7031 features an internal SPST RF switch that,
when combined with a few external components, allows
the transmit and receive pins to share a common anten-
na (see the Typical Application Circuit) . In receive
mode, the switch is open and the power amplifier is
shut down, presenting a high impedance to minimize
the loading of the LNA. In transmit mode, the switch
closes to complete a resonant tank circuit at the PA out-
put and forms an RF short at the input to the LNA. In
this mode, the external passive components couple the
output of the PA to the antenna to protect the LNA input
from strong transmitted signals.
The switch state is controlled by the T/R pin (pin 22).
Drive T/R high to put the device in transmit mode; drive
T/R low to put the device in receive mode.
The XTAL oscillator in the MAX7031 is designed to pre-
sent a capacitance of approximately 3pF between the
XTAL1 and XTAL2 pins. In most cases, this corre-
sponds to a 4.5pF load capacitance applied to the
external crystal when typical PCB parasitics are added.
It is very important to use a crystal with a load
capacitance that is equal to the capacitance of the
MAX7031 crystal oscillator plus PCB parasitics. If a
crystal designed to oscillate with a different load
capacitance is used, the crystal is pulled away from its
stated operating frequency, introducing an error in the
reference frequency. Crystals designed to operate with
higher differential load capacitance always pull the ref-
erence frequency higher.
Low-Cost, 308MHz, 315MHz, and 433.92MHz
Transmit/Receive Antenna Switch
______________________________________________________________________________________
FSK Transceiver with Fractional-N PLL
Crystal Oscillator (XTAL)
In actuality, the oscillator pulls every crystal. The crys-
tal’s natural frequency is really below its specified fre-
quency, but when loaded with the specified load
capacitance, the crystal is pulled and oscillates at its
specified frequency. This pulling is already accounted
for in the specification of the load capacitance.
Additional pulling can be calculated if the electrical
parameters of the crystal are known. The frequency
pulling is given by:
where:
f
Cm is the motional capacitance of the crystal.
C
C
C
When the crystal is loaded as specified, i.e., C
C
f
PROCESS: CMOS
P
P
CASE
SPEC
LOAD
SPEC
is the amount the crystal frequency is pulled in ppm.
=
C
TOP VIEW
2
, the frequency pulling equals zero.
m
is the specified load capacitance.
is the case capacitance.
is the actual load capacitance.
⎛
⎜
⎝
25
26
27
28
29
30
31
32
C
+
CASE
24
1
23
2
1
+
C
22
3
LOAD
THIN QFN
MAX7031
21
4
Pin Configuration
20
Chip Information
5
−
C
19
6
CASE
18
7
17
1
+
8
C
SPEC
16
15
14
13
12
11
10
9
⎞
⎟
⎠
LOAD
x
10
15
6
=