Datasheet

Detailed Description
The MAX1470 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 as high
as 100kbps can be achieved.
The MAX1470 is designed to receive binary ASK data
on a 315MHz carrier. ASK modulation uses a difference
in amplitude of the carrier to represent logic 0 and logic
1 data.
Low-Noise Amplier
The LNA is a cascode amplifier with off-chip inductive
degeneration that achieves approximately 16dB of power
gain with a 2.0dB noise figure and an IIP3 of -18dBm. The
gain and noise figure is dependent on both the antenna
matching network at the LNA input, and the LC tank net-
work between the LNA output and the mixer inputs.
The off-chip inductive degeneration is achieved by con-
necting an inductor from LNASRC to AGND. This inductor
sets the real part of the input impedance at LNAIN, allow-
ing for a more flexible match for low-input impedance
such as a PC board trace antenna. A nominal value for
this inductor with a 50Ω input impedance is 15nH, but
is affected by PC board trace. See Typical Operating
Characteristics for the relationship between the induc-
tance and input impedance.
The LC tank filter connected to LNAOUT comprises L1
and C9 (see Typical Applications Circuit). L1 and C9 val-
ues are selected to resonate at the RF input frequency of
315MHz. The resonant frequency is given by:
PIN NAME FUNCTION
1 XTAL1 1st Crystal Input
2, 7 AV
DD
Positive Analog Supply Voltage for RF Sections. Decouple to AGND with 0.01µF capacitors.
3 LNAIN Low-Noise Amplier Input
4 LNASRC
Low-Noise Amplier Source. Connect inductor to ground to set LNA input impedance (see Low-Noise
Amplier section).
5, 10 AGND Analog Ground
6 LNAOUT Low-Noise Amplier Output
8 MIXIN1 1st Differential Mixer Input. Must be AC-coupled to driving input.
9 MIXIN2 2nd Differential Mixer Input. Must be AC-coupled to driving input.
11, 15, 16,
23, 24
I.C. Internally Connected. Do not make connection to these pins.
12 MIXOUT 330Ω Mixer Output
13 DGND Digital Ground
14 DV
DD
Positive Digital Supply Voltage. Decouple to DGND with a 0.01µF capacitor.
17 IFIN1 1st Differential Intermediate Frequency Limiter Amplier Input
18 IFIN2 2nd Differential Intermediate Frequency Limiter Amplier Input
19 DSP Positive Data Slicer Input
20 DSN Negative Data Slicer Input
21 OPP Noninverting Op Amp. Input for the Sallen-Key data lter.
22 DF Data Filter Feedback Node. Input for the feedback of the Sallen-Key data lter.
25 DATAOUT Digital Baseband Data Output
26 PDOUT Peak Detector Output
27
PWRDN
Power-Down Select Input. Drive this pin with a logic low to shut down the IC.
28 XTAL2 2nd Crystal Input
MAX1470 315MHz Low-Power, +3V Superheterodyne
Receiver
www.maximintegrated.com
Maxim Integrated │ 6
Pin Description