MAX7031MATJ50+ Maxim Integrated Products, MAX7031MATJ50+ Datasheet - Page 13

• 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

generates a 100mV
control voltage is then filtered and sliced by the base-
band circuitry.
The FSK demodulator PLL requires calibration to over-
come variations in process, voltage, and temperature.
This is done by cycling the ENABLE pin when the
AUTOCAL pin is a logic 1. If the AUTOCAL pin is a
logic 0, calibration cannot occur.
The data filter for the demodulated data is implemented
as a 2nd-order, lowpass Sallen-Key filter. The pole
locations are set by the combination of two on-chip
resistors and two external capacitors. Adjusting the
value of the external capacitors changes the corner fre-
quency to optimize for different data rates. Set the cor-
ner frequency in kHz to approximately 2 times the
fastest expected Manchester data rate in kbps from the
transmitter (1.0 times the fastest expected NRZ data
rate). Keeping the corner frequency near the data rate
rejects any noise at higher frequencies, resulting in an
increase in receiver sensitivity.
The configuration shown in Figure 2 can create a
Butterworth or Bessel response. The Butterworth filter
offers a very-flat-amplitude response in the passband
Figure 3. Generating Data Slicer Threshold Using a Lowpass
Filter
Table 2. Coefficients to Calculate C
and C
FILTER TYPE
Butterworth
(Q = 0.707)
(Q = 0.577)
Bessel
F2
Low-Cost, 308MHz, 315MHz, and 433.92MHz
DATA
MAX7031
SLICER
DATA
______________________________________________________________________________________
C
P-P
FSK Transceiver with Fractional-N PLL
DS-
signal on the control line. This
1.3617
1.414
a
R
DS+
1.000
0.618
Data Filter
b
F1
and a rolloff rate of 40dB/decade for the two-pole filter.
The Bessel filter has a linear phase response, which
works well for filtering digital data. To calculate the
value of the capacitors, use the following equations,
along with the coefficients in Table 2:
where f
For example, choose a Butterworth filter response with
a corner frequency of 5kHz:
Choosing standard capacitor values changes C
470pF and C
Circuit , C
respectively.
Figure 4. Generating Data Slicer Threshold Using the Peak
Detectors
C
C
C
F
F
1
2
DATA
is the desired 3dB corner frequency.
MAX7031
=
=
F1
( .
1 414 100
( )(
SLICER
4 100
DATA
F2
and C
to 220pF. In the Typical Application
C
C
)(
F
F
k
1
2
Ω
1 414
=
=
F2
C
.
)( .
1 000
k
a
PEAK
DET
4 100
3 14 5
.
Ω
(
(
100
PDMAX
are named C16 and C17,
)( .
3 14 5
)(
R
k
k
Ω
b
Ω
a
kHz
)( )( )
)( )( )
)(
π
π
kHz
)
f
≈
R
c
f
c
225
)
PEAK
DET
≈
PDMIN
pF
450
C
pF
F1
13
to