Datasheet

MAX7034
315MHz/434MHz ASK Superheterodyne
Receiver
8
Functional Diagram
LNAOUT MIXIN1 MIXIN2
0˚
90˚
IFIN1MIXOUT IFIN2
RSSI
R
DF2
100kΩ
R
DF1
100kΩ
DIVIDE
BY 64
VCO
LOOP
FILTER
PHASE
DETECTOR
CRYSTAL
DRIVER
POWER-
DOWN
IF LIMITING
AMPS
7
LNASRC
DATA
SLICER
DATA
FILTER
Q
∑
I
IMAGE
REJECTION
3.4V REG
24
2
IRSEL
13
5, 10
AVDD
V
DD5
AVDD
DVDD
DGND
AGND
LNAIN
3
XTALSEL
16
XTAL1
1
XTAL2
28
SHDN
27
DATAOUT
25
DSN
20
DSP
23
DFO
19
PDOUT
26
OPP
21
DFFB
22
4 15 6 8 9 11 12 17 18
EN_REG
÷2
÷1
MAX7034
LNA
14
Detailed Description
The MAX7034 CMOS superheterodyne receiver and a
few external components provide the complete receive
chain from the antenna to the digital output data.
Depending on signal power and component selection,
data rates can be as high as 33kbps Manchester
(66kbps NRZ).
The MAX7034 is designed to receive binary ASK data
modulated in the 300MHz to 450MHz frequency range.
ASK modulation uses a difference in amplitude of the
carrier to represent logic 0 and logic 1 data.
Voltage Regulator
For operation with a single +4.5V to +5.5V supply voltage,
connect V
DD5
and the EN_REG pin to the supply voltage.
An on-chip voltage regulator drives one of the AVDD pins
(pin 2) to approximately +3.4V. For proper operation,
DVDD and both AVDD pins must be connected together.
For operation with a single +3.0V to +3.6V supply voltage,
connect both the AVDD pins, DVDD, and V
DD5
to the
supply voltage and connect the EN_REG pin to ground
(which disables the internal voltage regulator). If the
MAX7034 is powered from +3.0V to +3.6V, the perfor-
mance is limited to the -40°C to +105°C range.
In either supply voltage mode, bypass V
DD5
, DVDD, and
the pin 7 AVDD pin to AGND with 0.01μF capacitors, and
the pin 2 AVDD to AGND with a 0.1μF capacitor, all
placed as close as possible to the pins.
Low-Noise Amplifier
The LNA is an nMOS cascode amplifier with off-chip
inductive degeneration. The gain and noise figures are
dependent on both the antenna matching network at
the LNA input and the LC tank network between the
LNA output and the mixer inputs.
The off-chip inductive degeneration is achieved by
connecting an inductor from LNASRC to AGND. This
inductor sets the real part of the input impedance at
LNAIN, allowing for a more flexible input impedance
match, such as a typical printed-circuit board (PCB)
trace antenna. A nominal value for this inductor with a
50Ω input impedance is 15nH, but is affected by the
PCB trace.
The LC tank filter connected to LNAOUT comprises L1
and C9 (see the Typical Application Circuit ). Select L1
and C9 to resonate at the desired RF input frequency.
The resonant frequency is given by:
where:
L
TOTAL
= L1 + L
PARASITICS
.
C
TOTAL
= C9 + C
PARASITICS
.
f
LC
RF
TOTAL TOTAL
=
×
1
2π