Datasheet FX118DW, FX118P Datasheet (Consumer Microcircuits Limited)

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

Application Information

C

3

V

DD

C

2

X

C

1

1

R

1

XTAL

LPF(1) OUT

C

4

B MOD(1) IN

V

C1 OUT

CHANNEL 1 OUTPUT

CHANNEL 1 INPUT

R

C

2

5 R

R

3

C1 AMP OUT

C1 IN

1
2
3

4

SS

FX118

5
6
7

16
15
14
13
12
11
10

89

V

SS

XTAL/CLOCK

V

DD

LPF(2) OUT

B MOD(2) IN

V

BIAS

C2 OUT

C2 AMP OUT

C2 IN

C

V

SS

R

5

Component Value

R

1

R2 R3 C
R4 R5 C

C

1

5
6

= 1.0MΩ

See Note
See Note

47pF

C

2

C

3

C

4

T

olerances C = ±20% R = ±10%

= 33pF

0.47µF

1.0µF

C

7

C

8

X

1

NOTES 1. Configurations R2, R3, C5 and R4, R5, C6 should be chosen with respect to the specific application.

2. Operation of any CML microcircuit without a Xtal or clock input may cause device damage. To minimise damage
in the event of a Xtal/drive failure, it is recommended that the power rail (VDD) is fitted with a current limiting
device (resistor or fast-reaction fuse).

8

C

7

CHANNEL 2 OUTPUT

CHANNEL 2 INPUT

= 1.0µF

C

4

6

1.0µF

4.433619MHz

Fig.2 Recommended External Components

Rx Channel

RF

IF

AMP

MODULATION

FM

Tx Channel

Rx Channel

IF

AMP

MODULATION

FM

Tx Channel

DETECTION

FM

PRE-

EMPHASIS

DETECTION

FM

PRE-

EMPHASIS

AMP

AMP

AMP

AMP

RF

RF

RF

CHANNEL 1 (C1)

CHANNEL 1 (C1)

CHANNEL 2 (C2)

CHANNEL 2 (C2)

BASE UNIT

FX118

FX118

HANDHELD UNIT

DE-EMPHASIS

DE-EMPHASIS

AF AMP

AF AMP

AF AMP

HYBRID

TRANSFORMER

AF AMP

TELEPHONE

LINE

Fig.3 Example of the FX118 Employed in a Cordless Telephone Application

3

Application Information ......

Gain

+5

dB

0

-3

-10

-20

-30

-40

0.1 0.2 0.3 0.5 2.01.0 7.0

Audio Input Level = 275mVrms

V = 3.75V

DD

3.0

Frequency kHz

Fig.4 Typical Audio Frequency Response of a Single Scrambled or De-scrambled Channel

System Gains

When calculating the external components for the operation of the FX118 the following points should be considered:

(a) The Input Lowpass Filter has a (typical) gain of 0.5dB.

(b) The Balanced Modulator has a (typical) attenuation of 4.0dB.

(c) The Output Bandpass Filter has a (typical) gain of 4.5dB.

How the Inverter Works

Carrier Frequency

(1)

Input Voiceband Frequencies

(3)

minus

Input Voice Frequency

Speech Band

Carrier Frequency (3300Hz)

Generated On-Chip for Input to

Balanced Modulator

equals

Scrambled Voice Frequency

(2)

B

A

Lowpass Filtered Voiceband

Balanced Modulator

0

(4)

D

Bandpass Filtered Voiceband

after Mixing with the Carrier Frequency

in the Balanced Modulator

C

D

for Input to

1000Hz 2000Hz 3000Hz

B

C

A

Presented at the Ouput

0

1000 2000 3000

3300

0

Fig.5 A Pictorial Explanation of the FX118 “Scramble Operation”

4

1000 2000 3000

Specification

Absolute Maximum Ratings

Exceeding the maximum rating can result in device damage. Operation of the device outside the operating limits is not
implied.

Supply voltage -0.3 to 7.0V
Input voltage at any pin (ref V
Sink/source current (supply pins) +/- 30mA

(other pins) +/- 20mA
Total device dissipation @ T
Derating 10mW/°C

Operating temperature range: FX118DW/P -40°C to +85°C
Storage temperature range: FX118DW/P -40°C to +85°C

Operating Limits

All device characteristics are measured under the following conditions unless otherwise specified:
V

= 3.75V. T

DD

= 25°C. Xtal/Clock f0 = 4.433619MHz. Audio level 0dB ref: = 388mV rms @ 1.0kHz.

AMB

Characteristics See Note Min. Typ. Max. Unit
Static Values

Supply Voltage 3.0 3.75 5.5 V
Supply Current – 4.0 6.0 mA
Input Impedance (Amplifiers) 1.0 10.0 – MΩ
Output Impedance (LP Filters) – 2.0 – kΩ
Output Impedance (C1, C2 ) – 200 – Ω
Output Impedance (C1, C2 Amps) – 10.0 – kΩ

On-Chip Xtal Oscillator

R

IN

R

OUT

Inverter Gain – 10.0 – V/V
Gain/Bandwidth Product – 10.0 – MHz

Dynamic Values

Analogue Signal Input Levels -16.0 – 4.0 dB
SINAD 6 – 30.0 – dB
Unwanted Modulation Products 1, 2 – -40.0 – dB
Carrier Breakthrough 1, 2 – -55.0 – dB
Baseband Breakthrough 1, 2 – -40.0 – dB
Carrier Frequency – 3299 – Hz
Analogue Output Noise 3 – -42.0 – dB
Analogue Output Noise 5 – -46.0 – dBp

Filters
Input Lowpass Filter 1

Cut-Off Frequency (-3dB) – 3100 – Hz
Passband Ripple (300Hz - 3kHz) – ±1.0 – dB
Attenuation at 3.3kHz – 30.0 – dB
Attenuation at 3.6kHz – 45.0 – dB
Passband Gain – 0.5 – dB

Output Bandpass Filter 1, 4

Passband Frequencies 300 – 3000 Hz
Passband Ripple – ±1.0 – dB
Low Freq. Roll-Off <200Hz 12.0 – – dB/oct.
High Freq. – Attenuation at 3.4kHz – 48.0 – dB
Passband Gain 3.5 4.5 5.5 dB

Overall Modulated and De-Modulated Channel Response

Passband Frequencies (Tx and Rx Channel) 300 – 3000 Hz
Passband Ripple -3.0 – 2.0 dB
Low Freq. Roll-Off <250Hz 18.0 – – dB/oct.
High Freq. – Attenuation at 3.4kHz – 48.0 – dB
Passband Gain 4 – 0.5 – dB
Distortion 1 – 3.0 – %

= 0V) -0.3 to (V

SS

25°C 800mW Max.

AMB

10.0 – – MΩ
– 10.0 – kΩ

+ 0.3V)

DD

Notes:

1. Measured with an audio input level of -3.0dB.

2. With respect to a single modulated (scrambling) channel.

3. Measured with a short circuit input, at any analogue output, in a 30.0kHz bandwidth.

4. With Input Amplifier gain at 0dB.

5. Measured psophometrically weighted, at any analogue output.

6. Measured in a 30kHz bandwidth.

5

Package Outlines

The FX118 is available in the package styles outlined
below. Mechanical package diagrams and specifications
are detailed in Section 10 of this document.
Pin 1 identification marking is shown on the relevant
diagram and pins on all package styles number
anti-clockwise when viewed from the top.

Handling Precautions

The FX118 is a CMOS LSI circuit which includes input
protection. However precautions should be taken to
prevent static discharges which may cause damage.

FX118DW 16-pin S.O.I.C. (D4)

NOT TO SCALE

Max. Body Length 10.49mm
Max. Body Width 7.59mm

FX118P 16-pin plastic DIL (P3)

NOT TO SCALE

Max. Body Length 20.57mm
Max. Body Width 6.60mm

Ordering Information

FX118DW 16-pin S.O.I.C. (D4)
FX118P 16-pin plastic DIL (P3)

CML does not assume any responsibility for the use of any circuitry described. No circuit patent licences are implied
and CML reserves the right at any time without notice to change the said circuitry.

6