MAX1473EUI+T Maxim Integrated Products, MAX1473EUI+T Datasheet - Page 10

• Manufacturer Part Number: MAX1473EUI+T
• Description: RF Receiver IC RCV ASK 315MHZ/433MHZ
• Manufacturer: Maxim Integrated Products

Specifications of MAX1473EUI+T

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The PLL block contains a phase detector, charge
pump/integrated loop filter, VCO, asynchronous 64x
clock divider, and crystal oscillator driver. Besides the
crystal, this PLL does not require any external compo-
nents. The VCO generates a low-side local oscillator
(LO). The relationship between the RF, IF, and refer-
ence frequencies is given by:
where:
M = 1 (V
To allow the smallest possible IF bandwidth (for best sen-
sitivity), the tolerance of the reference must be minimized.
The IF section presents a differential 330Ω load to pro-
vide matching for the off-chip ceramic filter. The six
internal AC-coupled limiting amplifiers produce an
overall gain of approximately 65dB, with a bandpass fil-
ter-type response centered near the 10.7MHz IF fre-
quency with a 3dB bandwidth of approximately
11.5MHz. The RSSI circuit demodulates the IF by pro-
ducing a DC output proportional to the log of the IF sig-
nal level, with a slope of approximately 14.2mV/dB (see
the Typical Operating Characteristics ).
315MHz/433MHz ASK Superheterodyne
Receiver with Extended Dynamic Range
Table 1. Component Values for Typical Application Circuit
10
COMPONENT
______________________________________________________________________________________
C10
C11
C12
C13
C1
C2
C3
C4
C5
C6
C7
C8
C9
R1
L1
L2
L3
X1
X2
XTALSEL
f
REF
= V
Intermediate Frequency/RSSI
6.6128MHz or 13.2256MHz
VALUE FOR 433MHz RF
= (f
DD
10.7MHz ceramic filter
) or 2 (V
RF
- f
1500pF
0.47µF
0.01µF
0.01µF
100pF
100pF
100pF
220pF
470pF
220pF
IF
2.7pF
56nH
15nH
15nH
15pF
15pF
5kΩ
Phase-Locked Loop
)/(32
XTALSEL

M)
= 0V)
4.7547MHz or 9.5094MHz
VALUE FOR 315MHz RF
10.7MHz ceramic filter
1500pF
0.47µF
0.01µF
0.01µF
100pF
100pF
100pF
220pF
470pF
220pF
110nH
4.7pF
15pF
15pF
15nH
27nH
5kΩ
The AGC circuit monitors the RSSI output. When the
RSSI output reaches 2.05V, which corresponds to an RF
input level of approximately -57dBm, the AGC switches
on the LNA gain reduction resistor. The resistor reduces
the LNA gain by 35dB, thereby reducing the RSSI out-
put by about 500mV. The LNA resumes high-gain mode
when the RSSI level drops back below 1.45V (approxi-
mately -65dBm at RF input) for 150ms. The AGC has a
hysteresis of ~8dB. With the AGC function, the
MAX1473 can reliably produce an ASK output for RF
input levels up to 0dBm with modulation depth of 18dB.
The XTAL oscillator in the MAX1473 is designed to pre-
sent a capacitance of approximately 3pF between the
XTAL1 and XTAL2. If a crystal designed to oscillate
with a different load capacitance is used, the crystal is
pulled away from its stated operating frequency, intro-
ducing an error in the reference frequency. Crystals
designed to operate with higher differential load capac-
itance always pull the reference frequency higher. For
example, a 4.7547MHz crystal designed to operate
with a 10pF load capacitance oscillates at 4.7563MHz
with the MAX1473, causing the receiver to be tuned to
315.1MHz rather than 315.0MHz, an error of about
100kHz, or 320ppm.
Applications Information
Murata SFECV10.7 series
Depends on XTAL
Depends on XTAL
TOKO LL1608-FH
Murata LQP11A
Murata LQP11A
DESCRIPTION
± 0.1pF
Crystal Oscillator
10%
20%
10%
20%
20%
5%
5%
5%
5%
5%
5%
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