Philips PCD4440T Datasheet
INTEGRATED CIRCUITS
DATA SH EET
PCD4440T
Analog voice
scrambler/descrambler
Product specification
Supersedes data of October 1992
File under Integrated Circuits, IC03
1996 Dec 20
Philips Semiconductors Product specification
Analog voice scrambler/descrambler PCD4440T
CONTENTS
1 FEATURES
2 APPLICATIONS
3 GENERAL DESCRIPTION
6 PINNING INFORMATION
6.1 Pinning
6.2 Pin description
7.1 Scrambling
7.2 Power supply (VDD, VSS)
7.3 Oscillator (OSCI)
7.4 Splitting frequency and mode selection
7.5 Serial clock input (SCL), Serial data input (SDA)
7.6 Address input (A0)
7.7 I2C-bus data configuration
7.8 Signal input (IN), Signal output (OUT)
8I
8.1 Bit transfer
8.2 Start and stop conditions
8.3 System configuration
8.4 Acknowledge
8.5 Timing specifications
9 APPLICATIONS
10 HANDLING
11 LIMITING VALUES
12 CHARACTERISTICS
14.1 Introduction
14.2 Reflow soldering
14.3 Wave soldering
14.4 Repairing soldered joints
15 DEFINITIONS+
16 LIFE SUPPORT APPLICATIONS
17 PURCHASE OF PHILIPS I2C COMPONENTS
2
C BUS INTERFACE
1996 Dec 20 2
Philips Semiconductors Product specification
Analog voice scrambler/descrambler PCD4440T
1 FEATURES
• Scrambler or descrambler function
• Scrambling in frequency domain
• Selectable split frequency (up to 10 selections per
second)
• Telephony-band filtering included
• No increase in bandwidth
• No external components required
• Small signal delay
• Insensitive to distortion and group delay of transmission
channel
2
• Control via serial I
• Low transfer loss of speech
• Mute option
• Transparent mode
• High signal input impedance
• Low signal output impedance
• Low power consumption.
4 ORDERING INFORMATION
C-bus
2 APPLICATIONS
• Cordless telephones
• Security telephones
• Portable phones
• Private Mobile Radio (PMR).
3 GENERAL DESCRIPTION
The PCD4440T is a silicon gate CMOS integrated circuit
intended to be used in cordless telephony, radio, and line
telecommunications products utilizing a microcontroller for
the control functions. The purpose of the device is to
prevent unauthorized ‘listening-in’ on conversations.
A major application is protection of the vulnerable radio link
between a CT0 type cordless handset and its base unit.
Analog scrambling/descrambling is based on the split
frequency method realized in a sophisticated
switched-capacitor technology. The PCD4440T is
compatible with most microcontrollers and communicates
via a two line bidirectional I
2
C-bus.
TYPE
NUMBER
PCD4440T SO8 plastic small outline package; 8 leads; body width 7.5 mm SOT176-1
NAME DESCRIPTION VERSION
PACKAGE
1996 Dec 20 3
Philips Semiconductors Product specification
Analog voice scrambler/descrambler PCD4440T
5 BLOCK DIAGRAM
handbook, full pagewidth
4
IN
LPF
BIAS GEN
LPF LPF
PCD4440T
LPF
128
SCL OSCI V
SDA A0
LPF
transparent
clocks
5
LPF
mute
CONTROL LOGICI2C-bus INTERFACE
76
3
DDVSS
OUT
MGG729
Fig.1 Block diagram.
1996 Dec 20 4
Philips Semiconductors Product specification
Analog voice scrambler/descrambler PCD4440T
6 PINNING INFORMATION
6.1 Pinning
handbook, halfpage
SCL
V
SS
IN
1
2
PCD4440T
3
4
MGG728
A0
8
OSCISDA
7
V
6
DD
OUT
5
Fig.2 Pin configuration.
6.2 Pin description SYMBOL PIN TYPE DESCRIPTION
2
SCL 1 I serial clock line (I
SDA 2 I serial data line (I
V
SS
3 P negative Supply
C-bus)
2
C-bus)
IN 4 I signal input
OUT 5 O signal output
V
DD
6 P positive supply
OSCI 7 I oscillator input
A0 8 I slave address input (I
2
C-bus)
7.1 Scrambling
The PCD4440Taccomplishes this task by first filtering the
incoming signal, limiting the bandwidth to 3500 Hz. Then
the signal is split into a high (> fs) and a low (< fs) frequency
band. Both frequency bands are inverted and added again
to provide a single output signal. Values for 9 split
frequencies fS can be controlled by a scramble code table
in the microcontroller. Control of these split frequencies is
accomplished via the serial two-wire I2C-bus. In addition to
the split frequencies (fs), a transparent mode and mute
instruction can be selected (see Table 1).
Figure 3 shows the signal path for both bands. The lower
band path (on the left side of the diagram) operates on
frequencies f ≤ f
(Split Frequency), the upper band path
s
(on the right side) on frequencies f ≥ fs.
The input signal contains frequencies from f1up to f2.
In scrambling mode, the output signal is band limited from
fl (300 Hz) to fh(3500 Hz). In the left path, the input signal
is first limited to fs. The following modulator inverts the
lower band. fl is folded up to fs, fs down to fl. In general, an
input frequency fin is folded to f
out=fs+fl−fin
. Finally the
folded signal is band limited to fs again.
In the right path, the input signal is first limited to fh.
The following modulator inverts the upper band. fs is folded
up to fh, fh down to fs. In general, an input frequency fin is
folded to f
out=fs+fh−fin
. Finally, the folded signal is band
limited to fh again. In the last step, the bands are added
and buffered.
7 FUNCTIONAL DESCRIPTION
To provide privacy for the end user of a cordless telephone
set, the radio-link audio signal must be scrambled. In the
microphone of the handset and the incoming telephone
line audio path of the base unit a scrambler circuit has to
be implemented. Consequently the audio signal to the
telephone line and to the earpiece must be descrambled.
Both functions can be fulfilled by the PCD4440T by simply
inserting it in the audio path.
1996 Dec 20 5
Because of the symmetry of the scrambling process,
descrambling is achieved by passing the signal through
another PCD4440T.
In the transparent mode, the input signal is band limited to
3500 Hz. Frequencies from 0 to 300 Hz are not filtered
out.
Philips Semiconductors Product specification
Analog voice scrambler/descrambler PCD4440T
handbook, full pagewidth
A
ab cd e f
0
f
1
LPF
1a
A
ab c ab cd e
0ff
f
f
1
A
0ff
f
1
s
l
f
m1 = fl + fs
c
ab
f
s
l
ab c
LPF
1b
f
fhf2ff
s
l
A
f
0ff
f
l
1
f
m2 = fh + fs
A
0ff
f
f
1
l
LPF
2a
f
s
f
s
LPF
2b
f
h
2
aabbccddee
f
h
2
A
bc
0ff
f
f
1
s
l
A
0ff
f
f
1
l
bcde
f
s
A
0ff
h
Fig.3 Scrambler signal path.
1996 Dec 20 6
de
f
f
2
f
f
1
s
l
f
h
2
MGG730
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