CML Semiconductor Products
PRODUCT INFORMATION
FX118
Features/Applications
Frequency Inversion Scrambling
Full-Duplex Operation
High Baseband and Carrier
Rejection
Audio Lowpass and Bandpass
Filtering On-Chip
Xtal Oscillator Stabilty
Duplex Frequency Inverter
for Cordless Telephones
Publication D/118/3 July 1994
Low Power Requirement
(3.0 Volt Minimum)
Cordless Telephones
Base and Handheld Applications
Input Gain Adjustment
Plastic DIL and S.O.I.C. Package
Styles
C1 AMP OUT
LPF(1)
LPF(1) OUT
B MOD(1) IN
BAL MOD (1)
BPF(1)
C1 IN
C1 OUT
+0.5dB
INPUT AMP
CHANNEL 1 (C1)
-4.0dB
+4.0dB
V
BIAS
XTAL/CLOCK
XTAL
CLOCKS
and
LOGIC
FILTER CLOCKS
111kHz
CARRIER
3.3kHz
V
DD
V
BIAS
V
SS
FX118
V
BIAS
INPUT AMP
CHANNEL 2 (C2)
-4.0dB
C2 OUT
C2 IN
+0.5dB
LPF(2)
BAL MOD (2)
+4.0dB
BPF(2)
C2 AMP OUT
LPF(2) OUT
B MOD(2) IN
Fig.1 FX118 Duplex Frequency Inverter
Brief Description
The FX118 is a low-power, full-duplex frequency
inverter available to provide voice privacy for cordless
telephone systems by mixing the incoming audio with an
internally produced carrier frequency (3.3kHz).
This chip contains two completely separate audio
channels (C1 and C2) each comprising a “component-
adjustable” input amplifier, a 10th-order lowpass filter, a
balanced modulator and a 14th-order bandpass filter
output.
The on-chip modulation process has the properties of
high baseband and carrier frequency rejection which
when combined with high-order output filtering,
produces a high-quality recovered voiceband audio.
1
The frequency stability of the FX118 is achieved by an
on-chip oscillator employing an external 4.433619MHz
Xtal or clock input to produce the common carrier
frequency and the sampling clocks for the switched
capacitor low and bandpass filters.
This microcircuit has a low power requirement of 3.0
volts (min.) and is encapsulated in either 16-pin DIL or
small outline SMD (S.O.I.C.) plastic packages both of
which are of a physical size suitable for either base or
handset type telephone instruments as well as battery-
portable and mobile communications systems.
CMLMICRO [ CML MICROCIRCUITS ]
