Datasheet

is required due to the on-chip image-rejection architec-
ture. The IF output is driven by a source follower biased to
create a driving-point impedance of 330Ω; this provides a
good match to the off-chip 330Ω ceramic IF filter.
The IRSEL pin is a logic input that selects one of the
three possible image-rejection frequencies. When V
IRSEL
= 0V, the image rejection is tuned to 315MHz. V
IRSEL
=
V
DD5
/2 tunes the image rejection to 375MHz, and V
IRSEL
= V
DD5
tunes the image rejection to 433MHz. The IRSEL
pin is internally set to V
DD5
/2 (image rejection at 375MHz)
when it is left unconnected, thereby eliminating the need
for an external V
DD5
/2 voltage.
Phase-Locked Loop
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 components. The
VCO generates a low-side LO. The relationship between
the RF, IF, and crystal frequencies is given by:
RF IF
XTAL
f - f
f
32 M
=
×
where:
M = 1 (V
XTALSEL
= V
DD5
) or 2 (V
XTALSEL
= 0V)
To allow the smallest possible IF bandwidth (for best sen-
sitivity), minimize the tolerance of the reference crystal.
Table 1. Component Values for Typical Application Circuit
*Wire wound recommended.
**Crystal frequencies shown are for ÷64 (V
XTALSEL
= 0V) and ÷32 (V
XTALSEL
= V
DD
)
COMPONENT VALUE FOR f
RF
= 433MHz VALUE FOR f
RF
= 315MHz DESCRIPTION
C1 100pF 100pF 5%
C2 2pF 4pF ± 0.1pF
C3 100pF 100pF 5%
C4 100pF 100pF 5%
C5 1500pF 1500pF 10%
C6 220pF 220pF 5%
C7 470pF 470pF 5%
C8 0.47µF 0.47µF 20%
C9 220pF 220pF 10%
C10 0.01µF 0.01µF 20%
C11 0.1µF 0.1µF 20%
C12 15pF 15pF Depends on XTAL
C13 15pF 15pF Depends on XTAL
C14 0.01µF 0.01µF 20%
C15 0.01µF 0.01µF 20%
L1 56nH 120nH 5% or better*
L2 15nH 15nH 5% or better*
L3 15nH 27nH 5% or better*
R1 5.1kΩ 5.1kΩ 5%
R2 Open Open —
R3 Short Short —
X1 (÷64) 6.6128MHz** 4.7547MHz** Crystek or Hong Kong Crystal
X1 (÷32) 13.2256MHz** 9.5094MHz** Crystek or Hong Kong Crystal
Y1 10.7MHz ceramic lter 10.7MHz ceramic lter Murata
MAX7033 315MHz/433MHz ASK Superheterodyne
Receiver with AGC Lock
www.maximintegrated.com
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