KESRX05
IFFLT1
IFDC1
IFIN
IFDC2
V
CC
IFOUT
V
CC
RF
MIXIP
RFOP
V
EE
RF
RFIN
AGC
PEAK
DATAOP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
IFFLT2
RSSI
DETB
PD
XTAL1
XTAL2
DF0
DF1
DF2
VCO1
VCO2
V
EE
LF
DSN
KESRX05
22
21
20
19
18
17
16
15
Figure 2 Pin connections (top view)
DESCRIPTION
The single conversion superheterodyne receiver
approach is now generally considered the way forward
for ISM band type applications because of lower cost,
superior selectivity, lower radiation, and flexibility over
other techniques. For power-conscious, hand-held
applications KESRX05 provides improved performance
and flexibility on a lower 3·0V supply and a power down
feature allows faster switch-on times for use in a pulsed
power saving mode.
Although this is a relatively simple receiver, the flexibility
of using an external IF filter allows the designer to
choose both the selectivity and the IF in order to optimise
Pin
1
Name
IFFLT1
Function
Noise reducing IF filter
A simple LC noise reduction filter (L5 and C7) is
connected between pins 1 (IFFLT1 ) and 28 (IFFLT2)
to reduce the noise contribution from the earlier
stages of the logathrimic amplifier. The LC filter helps
to reduce the bandwidth of the log amplifier from
approximately 45MHz to typically 1MHz, preventing
wideband noise from being detected as a signal. To
reduce the Q of the simple LC circuit, an external
damping resistor in parallel with L5, C7. However,
the preferred method to a damping resistor is to lower
the Q of L5 or increase the tolerances of L5 and C7.
For further information refer to the
IFAmp /RSSI Detector section of the Functional Description.
Table 1 Pin descriptions
Cont…
the performance for a wide range of applications and
locations world wide.
T
he KESRX05, with its anti-jamming detector circuit, is
an ideal ASK/ OOK receiver for difficult reception areas
caused by interference such as amateur radio repeater
stations and wireless stereo headphones. Operation is
possible with interfering signals which are more than
20dB stronger than the wanted signal (IF bandwidth =
470kHz.), without the cost penalities of increased IF se-
lectivity and frequency accuracy.
Figure 1 is the system block diagram, with an external
ceramic IF filter, SAW fillter and noise reduction filter.
Schematic
V
CC
10k
IFFLT1
10k
IFFLT2
2
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
