MAX1470 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

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MAX1470

315MHz Low-Power, +3V Superheterodyne Receiver

Maxim Integrated 

315MHz Low-Power, +3V Superheterodyne

Receiver

MAX1470

DATA

SLICER

25

DATA OUT

DATA

FILTER

20

19

DSN

DSP

C4

R1

MAX1470

DATA

SLICER

25

DATA OUT

20

19

DSN

DSP

25kΩ

47nF

DATA

FILTER

26

PDOUT

250kΩ

47nF

Figure 2. Generating Data Slicer Threshold

Figure 3. Using PDOUT for Faster Startup

peak detector to dynamically follow peak changes of

the data filter output voltage. For faster receiver startup,

the circuit shown in Figure 3 can be used.

433.92MHz Band

The MAX1470 can be configured to receive ASK modu-

lated data with carrier frequency ranging from 250MHz

to 500MHz. Only a small number of components need

to be changed to retune the RF section to the desired

RF frequency.

Table 2 shows a list of changed components and their

values for a 433.92MHz RF; all other components

remain unchanged.

The integrated image rejection of the MAX1470 is

specifically designed to function with a 315MHz input

frequency by attenuating any signal at 293.6MHz. The

benefit of the on-chip image rejection is that an external

SAW filter is not needed, reducing cost and the inser-

tion loss associated with SAW filters. The image rejec-

tion cannot be retuned for different RF input

frequencies and therefore is degraded. The image

rejection at 433.92MHz is typically 39dB.

Layout Considerations

A properly designed PC board 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

radiation. At high frequencies, trace lengths that are

approximately 1/20 the wavelength or longer become

antennas. For example, a 2in trace at 315MHz can act

as an antenna.

Keeping the traces short also reduces parasitic induc-

tance. Generally, 1in of a PC board trace adds about

20nH of parasitic inductance. The parasitic inductance

can have a dramatic effect on the effective inductance.

For example, a 0.5in trace connecting a 100nH induc-

tor adds an extra 10nH of inductance or 10%.

To reduce the parasitic inductance, use wider traces

and a solid ground or power plane below the signal

traces. Using a solid ground plane can reduce the par-

asitic inductance from approximately 20nH/in to 7nH/in.

Also, use low-inductance connections to ground on all

GND pins, and place decoupling capacitors close to all

VDD connections.

Table 2. Changed Component Values for

433.92MHz

COMPONENT

C9

L1

L2

Y1

VALUE FOR 433MHz RF

1.0pF

15nH

56nH

6.6128MHz

Note: These values are affected by PC board layout.

Chip Information

TRANSISTOR COUNT: 1835

PROCESS: CMOS

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