MAX7033EUI+T Maxim Integrated Products, MAX7033EUI+T Datasheet - Page 13

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MAX7033EUI+T

Manufacturer Part Number
MAX7033EUI+T
Description
RF Receiver IC RX 315MHZ/433MHZ ASK
Manufacturer
Maxim Integrated Products
Type
Receiverr
Datasheet

Specifications of MAX7033EUI+T

Package / Case
TSSOP-28
Operating Frequency
450 MHz
Operating Supply Voltage
3.3 V, 5 V
Maximum Operating Temperature
+ 105 C
Minimum Operating Temperature
- 40 C
Mounting Style
SMD/SMT
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
filter output. Both comparator inputs are accessible off-
chip to allow for different methods of generating the
slicing threshold, which is applied to the second com-
parator input.
The suggested data slicer configuration uses a resistor
(R1) connected between DSN and DSP with a capaci-
tor (C4) from DSN to DGND (Figure 3). This configura-
tion averages the analog output of the filter and sets the
threshold to approximately 50% of that amplitude. With
this configuration, the threshold automatically adjusts
as the analog signal varies, minimizing the possibility
for errors in the digital data. The values of R1 and C4
affect how fast the threshold tracks to the analog ampli-
tude. Be sure to keep the corner frequency of the RC
circuit much lower than the lowest expected data rate.
Note that a long string of zeros or ones can cause the
threshold to drift. This configuration works best if a cod-
ing scheme, such as Manchester coding, which has an
equal number of zeros and ones, is used.
To prevent continuous toggling of DATAOUT in the
absence of an RF signal due to noise, add hysteresis to
the data slicer as shown in Figure 4.
The peak-detector output (PDOUT), in conjunction with
an external RC filter, creates a DC output voltage equal
to the peak value of the data signal. The resistor pro-
vides a path for the capacitor to discharge, allowing the
peak detector to dynamically follow peak changes of
the data-filter output voltage. For faster data slicer
response, use the circuit shown in Figure 5.
A properly designed PCB 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 act as antennas.
Keeping the traces short also reduces parasitic induc-
tance. Generally, 1in of a PCB trace adds about 20nH
of parasitic inductance. The parasitic inductance can
have a dramatic effect on the effective inductance of a
passive component. For example, a 0.5in trace con-
necting a 100nH inductor adds an extra 10nH of induc-
tance 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 power-supply pins.
______________________________________________________________________________________
315MHz/433MHz ASK Superheterodyne
Layout Considerations
Peak Detector
Receiver with AGC Lock
Figure 3. Generating Data Slicer Threshold
Figure 4. Generating Data Slicer Hysteresis
Figure 5. Using PDOUT for Faster Startup
R1
R2
25
DATAOUT
25
DATAOUT
*OPTIONAL
25
DATAOUT
47nF
DSN
DATA
SLICER
C4
20
DSP
DATA
SLICER
DATA
SLICER
MAX7033
23
20
DSN
25kΩ
R3
DSP
23
MAX7033
R1
C4
DSN
20
DSP
23
19
DFO
MAX7033
R4
19
DFO
PDOUT
19
DFO
26
13

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