Micrel, Inc.

MICRF002/RF022

July 2008

10

M9999-070808

for the vast majority of applications. If adjustment is

required the constant may be varied by adding a resistor in

must be determined on a case by case basis.

Step 5: Selecting The Demod Filter Bandwidth

The inputs SEL0 and SEL1 control the demodulator filter

bandwidth in four binary steps (625Hz to 5000Hz in sweep,

1250Hz to 10000Hz in fixed-mode), see Table 3.

Bandwidth must be selected according to the application.

The demodulator bandwidth should be set according to

Equation 8:

(8)

width

pulse

Shortest

0.65

bandwidth

Demoulator

−

=

It should be noted that the values indicated in Table 1 are

nominal values. The filter bandwidth scales linearly with

frequency so the exact value will depend on the operating

frequency. Refer to the “Electrical Characteristics” for the

exact filter bandwidth at a chosen frequency.

Demodulator Bandwidth

SEL0

SEL1

Sweep-Mode

Fixed-Mode

1

1

5000Hz

10000Hz

0

1

2500Hz

5000Hz

1

0

1250Hz

2500Hz

0

0

625Hz

1250Hz

Table 1. Nominal Demodulator Filter Bandwidth vs.

SEL0, SEL1 and Operating Mode