Consumer Microcircuits Limited FX118DW, FX118P Datasheet
Features/Applications
CML Semiconductor Products
PRODUCT INFORMATION
Duplex Frequency Inverter
FX118
for Cordless Telephones
Publication D/118/3 July 1994
Frequency Inversion Scrambling
Full-Duplex Operation
High Baseband and Carrier
Rejection
Audio Lowpass and Bandpass
Filtering On-Chip
Xtal Oscillator Stabilty
C1 AMP OUT
C1 IN
INPUT AMP
XTAL/CLOCK
XTAL
INPUT AMP
C2 IN
V
BIAS
V
BIAS
LPF(1) OUT B MOD(1) IN
LPF(1)
+0.5dB
+0.5dB
LPF(2) BAL MOD (2)
CHANNEL 1 (C1)
CHANNEL 2 (C2)
LPF(2) OUT B MOD(2) INC2 AMP OUT
CLOCKS
and
LOGIC
FILTER CLOCKS
111kHz
BAL MOD (1) BPF(1)
-4.0dB
CARRIER
3.3kHz
-4.0dB
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 OUT
+4.0dB
V
DD
V
BIAS
FX118
+4.0dB
BPF(2)
V
SS
C2 OUT
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 “componentadjustable” 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.
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 batteryportable and mobile communications systems.
1
Pin Number Function
FX118DW
FX118P
1
2
3
Xtal: Output of clock oscillator inverter.
No Internal Connection: It is recommended that, to improve noise conditions, this pin is connected to V
LPF(1) Out: The output of the Channel 1 Lowpass Filter. It is to be coupled to “B Mod(1) In” via a 1.0µF
.
SS
capacitor – see Figure 2.
4
B Mod(1) In: The input to Channel 1 balanced modulator. Internally biased at V
“LPF(1)” via a 1.0µF capacitor – see Figure 2.
V
5
6
7
: Negative supply (GND).
SS
C1 Out: The analogue output of Channel 1.
C1 Amp Output: Channel 1 amplifier with external components (see Figure 2) can be used to provide gain in
/2 it is to be coupled to
DD
the signal path.
10
11
12
13
14
8
9
C1 In: The negative input of Channel 1 Amplifier. Recommended external components are shown in Figure 2.
C2 In: The negative input of Channel 2 Amplifier. Recommended external components are shown in Figure 2.
C2 Amp Output: Channel 2 amplifier with external components (see Figure 2) can be used to provide gain in
the signal path.
C2 Out: The analogue output of Channel 2.
V
: The internal analogue bias line at VDD/2. It should be decoupled to VSS via a 1.0µF or greater capacitor.
BIAS
See Figure 2.
B Mod(2) In: The input to Channel 2 balanced modulator. Internally biased at V
“LPF(2)” via a 1.0µF capacitor – see Figure 2.
/2 it is to be coupled to
DD
LPF(2) Out: The output of the Channel 2 Lowpass Filter. It is to be coupled to “B Mod(2) In” via a 1.0µF
capacitor – see Figure 2.
15
16
VDD: The positive supply rail. A single positive supply voltage (3.0v – 5.0v) is required. Levels and voltages
within the Duplex Frequency Inverter are dependent upon this supply.
Xtal/Clock: 4.433619 MHz Xtal or externally derived clock is injected at this pin. See Figure 2. Operation of
the FX118 without a Xtal or clock input may cause device damage.
2
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