KESRX05
Pin
2
Name
IFDC1
Function
Log Amplifier DC Blocking Capacitor
Capacitors C3 and C4 provide DC blocking within
the high gain stage of the log amplifier. The log
amplifier has a small gain of greater than 80dB
between pins 3 (IFIN) and 27 (RSSI output)
Capacitors C3 and C4 eliminate DC offsets, allowing
the amplification of AC signals only.
For further information, refer to the IF Amp/RSSI De-
tector section of the Functional Description.
Schematic
181k
IFDC1
3·1k
181k
IFDC
950
IFIN
3
IFIN
Log Amp Input (IFamplifier input)
The bandwidth of KESRX05 is set by the external
ceramic filter CF1. Impedance matching from the
output of the ceramic filter to the input of the log
amplifier is achieved by an external shunt resistor
R9 in parallel with an internal resistor.
For further information please refer to the IF Interface
section of the Functional Description.
C3
INTERNAL
IFDC1
181k
R9
FROM
CF1
IFIN
3·1k
Matching circuit for CF1
4
5
6
IFDC2
V
CC
IFOUT
Log amplifier DC stability capacitor
Positive supply
IF output
The IF output drive is a voltage drive with a low output
impedance of 300Ω via an internal series resistor.
The IFOUT pin is designed for direct connection to
an external 10·7MHz FM ceramic filter with a typical
input impedance of 300Ω.
For further information refer to the IF Interface section
of the Functional Description.
See pin 2
300
IFOUT
50µA
7
8
V
CC
RF
MIXIP
Positive supply for RF circuits
Mixer input
To a first order approximation the input impedance
of the mixer at UHF frequencies is set by the internal
bias resistor and capacitor network. Effects of internal
and external stray parasitics ignored.
For further information refer to the AC Electrical
Characteristics.
Table 1 Pin descriptions (continued)
MIXIP
2k
2p
V
EE
RF
Cont…
3
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
