Philips Semiconductors
SA575
Low voltage compandor
Product specification
Replaces data of 1997 June 28
1997 Nov 07
RF COMMUNICATIONS PRODUCTS
IC17
Philips Semiconductors
Product specification
SA575
Low voltage compandor
2
1997 Nov 07
853-1665 18666
DESCRIPTION
The SA575 is a precision dual gain control circuit designed for low
voltage applications. The SA575's channel 1 is an expandor, while
channel 2 can be configured either for expandor, compressor, or
automatic level controller (ALC) application.
FEATURES
Operating voltage range from 3V to 7V
Reference voltage of 100mV
RMS
= 0dB
One dedicated summing op amp per channel and two extra
uncommitted op amps
600
drive capability
Single or split supply operation
Wide input/output swing capability
3000V ESD protection
APPLICATIONS
Portable communications
Cellular radio
Cordless telephone
Consumer audio
PIN CONFIGURATION
+VIN1
-VIN1
VOUT
1
RECT. IN1
CRECT1
COMP. IN1
VREF
GND
20 VCC
19 +VIN2
18 -VIN2
17 VOUT2
16 RECT.IN2
15 CRECT2
14 SUM OUT2
13 COMP.IN2
12 SUM NODE 2
11 GAIN CELL IN2
SUM OUT 1
D
1
and DK Packages
NOTE:
1. Available in large SOL package only.
GAIN CELL IN1
1
2
3
4
5
6
7
8
9
10
SR00703
Figure 1. Pin Configuration
Portable broadcast mixers
Wireless microphones
Modems
Electric organs
Hearing aids
ORDERING INFORMATION
DESCRIPTION
TEMPERATURE RANGE
ORDER CODE
DWG
20-Pin Plastic Small Outline Large
-40 to +85
C
SA575D
SOT163-1
20-Pin Plastic Shrink Small Outline Package (SSOP)
-40 to +85
C
SA575DK
SOT266-1
ABSOLUTE MAXIMUM RATINGS
SYMBOL
PARAMETER
RATING
UNITS
SYMBOL
PARAMETER
SA575
UNITS
V
CC
Single supply voltage
0.3 to 8
V
V
IN
Voltage applied to any other pin
0.3 to (V
CC
+0.3)
V
T
A
Operating ambient temperature range
-40 to +85
C
T
STG
Storage temperature range
-65 to +150
C
JA
Thermal impedance
SOL
112
C/W
SSOP
117
C/W
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
3
BLOCK DIAGRAM and TEST CIRCUIT
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
G
G
VREF
+
+
OP AMP
OP AMP
VCC
575
4.7
F
10
F
0.1
F
VCC
+5V
10
F
2.2
F
10
F
CRECT
1
F
VIN
VREF
VOUT
CRECT
2.2
F
10
F
VIN
+
+
+
+
+
+
+
+
+
VOUT
C3
GND
C6
GND
GND
GND
3.8k
3.8k
10k
10k
10k
10k
GND
R8
30k
R7
30k
C8
GND
C11
C10
R13
10k
C14
C15
VREF
10
F
SR00704
Figure 2. Block Diagram and Test Circuit
DC ELECTRICAL CHARACTERISTICS
Typical values are at T
A
= 25
C. Minimum and Maximum values are for the full operating temperature range: -40 to +85
C for SA575, except
SSOP package is tested at +25
C only. V
CC
= 5V, unless otherwise stated. Both channels are tested in the Expandor mode (see Test Circuit)
LIMITS
SYMBOL
PARAMETER
TEST CONDITIONS
SA575
UNITS
MIN
TYP
MAX
For compandor, including summing amplifier
V
CC
Supply voltage
1
3
5
7
V
I
CC
Supply current
No signal
3
4.2
5.5
mA
V
REF
Reference voltage
2
V
CC
= 5V
2.4
2.5
2.6
V
R
L
Summing amp output load
10
k
THD
Total harmonic distortion
1kHz, 0dB BW = 3.5kHz
0.12
1.5
%
E
NO
Output voltage noise
BW = 20kHz, R
S
= 0
6
30
V
0dB
Unity gain level
1kHz
-1.5
1.5
dB
V
OS
Output voltage offset
No signal
-150
150
mV
Output DC shift
No signal to 0dB
-100
100
mV
Gain cell input = 0dB, 1kHz
Rectifier input = 6dB, 1kHz
-1.0
1.0
dB
Tracking error relative to 0dB
Gain cell input = 0dB, 1kHz
Rectifier input = -30dB, 1kHz
-1.0
1.0
dB
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
4
DC ELECTRICAL CHARACTERISTICS
(cont.)
LIMITS
SYMBOL
PARAMETER
TEST CONDITIONS
SA575
UNITS
MIN
TYP
MAX
Crosstalk
1kHz, 0dB, C
REF
= 220
F
-80
-65
dB
For operational amplifier
V
O
Output swing
R
L
= 10k
V
CC
-0.4
V
CC
V
R
L
Output load
1kHz
600
CMR
Input common-mode range
0
V
CC
V
CMRR
Common-mode rejection ratio
60
80
dB
I
B
Input bias current
V
IN
= 0.5V to 4.5V
-1
1
A
V
OS
Input offset voltage
3
mV
A
VOL
Open-loop gain
R
L
= 10k
80
dB
SR
Slew rate
Unity gain
1
V/
s
GBW
Bandwidth
Unity gain
3
MHz
E
NI
Input voltage noise
BW = 20kHz
2.5
V
PSRR
Power supply rejection ratio
1kHz, 250mV
60
dB
NOTES:
1. Operation down to V
CC
= 2V is possible, but performance is reduced. See curves in Figure 7a and 7b.
2. Reference voltage, V
REF
, is typically at 1/2V
CC
.
FUNCTIONAL DESCRIPTION
This section describes the basic subsystems and applications of the
SA575 Compandor. More theory of operation on compandors can
be found in AN174 and AN176. The typical applications of the
SA575 low voltage compandor in an Expandor (1:2), Compressor
(2:1) and Automatic Level Control (ALC) function are explained.
These three circuit configurations are shown in Figures 3, 4, 5
respectively.
The SA575 has two channels for a complete companding system.
The left channel, A, can be configured as a 1:2 Expandor while the
right channel, B, can be configured as either a 2:1 Compressor, a
1:2 Expandor or an ALC. Each channel consists of the basic
companding building blocks of rectifier cell, variable gain cell,
summing amplifier and V
REF
cell. In addition, the SA575 has two
additional high performance uncommitted op amps which can be
utilized for application such as filtering, pre-emphasis/de-emphasis
or buffering.
Figure 6 shows the complete schematic for the applications demo
board. Channel A is configured as an expandor while channel B is
configured so that it can be used either as a compressor or as an
ALC circuit. The switch, S1, toggles the circuit between compressor
and ALC mode. Jumpers J1 and J2 can be used to either include
the additional op amps for signal conditioning or exclude them from
the signal path. Bread boarding space is provided for R1, R2, C1,
C2, R10, R11, C10 and C11 so that the response can be tailored for
each individual need. The components as specified are suitable for
the complete audio spectrum from 20Hz to 20kHz.
The most common configuration is as a unity gain non-inverting
buffer where R1, C1, C2, R10, C10 and C11 are eliminated and R2
and R11 are shorted. Capacitors C3, C5, C8, and C12 are for DC
blocking. In systems where the inputs and outputs are AC coupled,
these capacitors and resistors can be eliminated. Capacitors C4
and C9 are for setting the attack and release time constant.
C6 is for decoupling and stabilizing the voltage reference circuit.
The value of C6 should be such that it will offer a very low
impedance to the lowest frequencies of interest. Too small a
capacitor will allow supply ripple to modulate the audio path. The
better filtered the power supply, the smaller this capacitor can be.
R12 provides DC reference voltage to the amplifier of channel B.
R6 and R7 provide a DC feedback path for the summing amp of
channel B, while C7 is a short-circuit to ground for signals. C14 and
C15 are for power supply decoupling. C14 can also be eliminated if
the power supply is well regulated with very low noise and ripple.
DEMONSTRATED PERFORMANCE
The applications demo board was built and tested for a frequency
range of 20Hz to 20kHz with the component values as shown in
Figure 6 and V
CC
= 5V. In the expandor mode, the typical input
dynamic range was from -34dB to +12dB where 0dB is equal to
100mV
RMS
. The typical unity gain level measured at 0dB @ 1kHz
input was +0.5dB and the typical tracking error was +0.1dB for input
range of -30 to +10dB.
In the compressor mode, the typical input dynamic range was from
-42dB to +18dB with a tracking error +0.1dB and the typical unity
gain level was +0.5dB.
In the ALC mode, the typical input dynamic range was from -42dB to
+8dB with typical output deviation of +0.2dB about the nominal
output of 0dB. For input greater than +9dB in ALC configuration, the
summing amplifier sometimes exhibits high frequency oscillations.
There are several solutions to this problem. The first is to lower the
values of R6 and R7 to 20k
each. The second is to add a current
limiting resistor in series with C12 at Pin 13. The third is to add a
compensating capacitor of about 22 to 30pF between the input and
output of summing amplifier (Pins 12 and 14). With any one of the
above recommendations, the typical ALC mode input range
increased to +18dB yielding a dynamic range of over 60dB.
EXPANDOR
The typical expandor configuration is shown in Figure 3. The
variable gain cell and the rectifier cell are in the signal input path.
The V
REF
is always 1/2 V
CC
to provide the maximum headroom
without clipping. The 0dB ref is 100mV
RMS
. The input is AC
coupled through C5, and the output is AC coupled through C3. If in
a system the inputs and outputs are AC coupled, then C3 and C5
can be eliminated, thus requiring only one external component, C4.
The variable gain cell and rectifier cell are DC coupled so any offset
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
5
voltage between Pins 4 and 9 will cause small offset error current in
the rectifier cell. This will affect the accuracy of the gain cell. This
can be improved by using an extra capacitor from the input to Pin 4
and eliminating the DC connection between Pins 4 and 9.
The expandor gain expression and the attack and release time
constant is given by Equation 1 and Equation 2, respectively.
4V
IN
(avg)
3.8k x 100
A
where V
IN
(avg) = 0.95V
IN(RMS)
R
=
A
= 10k x C
RECT
= 10k x C4
Expandor gain =
Equation 2.
Equation 1.
COMPRESSOR
The typical compressor configuration is shown in Figure 4. In this
mode, the rectifier cell and variable gain cell are in the feedback
path. R6 and R7 provide the DC feedback to the summing amplifier.
The input is AC coupled through C12 and output is AC coupled
through C8. In a system with inputs and outputs AC coupled, C8
and C12 could be eliminated and only R6, R7, C7, and C13 would
be required. If the external components R6, R7 and C7 are
eliminated, then the output of the summing amplifier will motor-boat
in absence of signals or at extremely low signals. This is because
there is no DC feedback path from the output to input. In the
presence of an AC signal this phenomenon is not observed and the
circuit will appear to function properly.
The compressor gain expression and the attack and release time
constant is given by Equation 3 and Equation 4, respectively.
4V
IN
(avg)
3.8k x 100
A
where V
IN
(avg) = 0.95V
IN(RMS)
R
=
A
= 10k x C
RECT
= 10k x C4
1/2
Compressor gain =
Equation 3.
Equation 4.
AUTOMATIC LEVEL CONTROL
The typical Automatic Level Control circuit configuration is shown in
Figure 5. It can be seen that it is quite similar to the compressor
schematic except that the input to the rectifier cell is from the input
path and not from the feedback path. The input is AC coupled
through C12 and C13 and the output is AC coupled through C8.
Once again, as in the previous cases, if the system input and output
signals are already AC coupled, then C12, C13 and C8 could be
eliminated. Concerning the compressor, removing R6, R7 and C7
will cause motor-boating in absence of signals. C
COMP
is necessary
to stabilize the summing amplifier at higher input levels. This circuit
provides an input dynamic range greater than 60dB with the output
within +0.5dB typical. The necessary design expressions are given
by Equation 5 and Equation 6, respectively.
4V
IN
(avg)
3.8k x 100
A
R
=
A
= 10k x C
RECT
= 10k x C9
Equation 5.
Equation 6.
ALC gain =
2.2
F
10
F
10
F
VREF
G
EXP IN
EXP OUT
10k
C5
9
4
3.8k
5
C4
C3
10k
7
6
8
SR00705
Figure 3. Typical Expandor Configuration
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
6
2.2
F
4.7
F
10
F
10
F
1
F
VREF
G
R6
R7
30k
30k
C7
8
12
14
COMP IN
COMP OUT
C13
11
16
10k
3.8k
15
C9
10k
13
C12
C8
SR00706
Figure 4. Typical Compressor Configuration
2.2
F
10
F
10
F
VREF
G
1
F
4.7
F
ALC IN
ALC OUT
8
12
C12
13
16
10k
16
C9
10k
11
14
C13
R6
R7
30k
30k
C COMP
22pF
C8
C7
3.8k
SR00707
Figure 5. Typical ALC Configuration
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
7
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
G
G
VREF
+
+
OP AMP
OP AMP
VCC
575
10
F
4.7
F
10
F
V
REF
VREF
10
F
0.1
F
VCC
-5V
47
F
2.2
F
10
F
1
F
10
F
R1
C1
EXP
OUT
EXP
IN
C2
R2
C4
C5
J1
C6
GND
10k
10k
10k
3.8k
3.8k
10k
COMP/
ALC
IN
COMP/
ALC
OUT
R7
30k
C7
30k
R6
ALC
COMP
C10
R10
C9
R11
C11
J2
C13
R12
10k
C14
C15
C12
C8
C3
S1
2.2
F
SR00708
Figure 6. SA575 Low Voltage Expandor/Compressor/ALC Demo Board
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
8
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
50
25
0
25
50
75
100
UNITY GAIN ERROR (dB)
TEMPERATURE (
C)
a. Unity Gain Error vs Temperature and V
CC
4.4
50
25
0
25
50
75
100
I
TEMPERATURE (
C)
4.2
4.0
3.8
3.6
3.4
3.2
3.0
CC
(mA)
VCC 7V
VCC 5V
VCC 3V
VCC 2V
b. I
CC
vs Temperature and V
CC
VCC 7V
VCC 5V
VCC 3V
VCC 2V
SR00709
Figure 7. Temperature and V
CC
Curves
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
9
TYPICAL PERFORMANCE CHARACTERISTICS
10
100
1000
10000
30000
8
6
4
2
0
2
4
6
8
10
12
14
16
18
20
22
INPUT
OUTPUT
GENERAL DIAGRAM
VCC = 5V
10
F
G
4.7
F
REC
SUM
(2020kHz)
OUTPUT LEVEL
(dB)
FREQUENCY (Hz)
10dB IN
0dB IN
-40dB IN
SR00710
Figure 8. Compressor Output Frequency Response
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
10
TYPICAL PERFORMANCE CHARACTERISTICS
(continued)
10
100
1000
10000
30000
8
6
4
2
0
2
4
6
8
10
12
14
16
18
20
22
INPUT
OUTPUT
GENERAL DIAGRAM
VCC = 5V
10
F
G
4.7
F
REC
SUM
(2020kHz)
OUTPUT LEVEL
(dB)
FREQUENCY (Hz)
2.5dB IN
0dB IN
-10dB IN
SR00711
Figure 9. Expandor Output Frequency Response
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
11
+10dB
100mV
0dB
10dB
20dB
30dB
+5dB
0dB
5dB
10dB
15dB
+10dB
100mV
0dB
10dB
20dB
30dB
COMPRESSION
EXPANSION
COMPRESSOR IN
EXPANDOR OUT
}
}
40dB
50dB
20dB
25dB
40dB
50dB
SR00712
Figure 10. The Companding Function
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
12
SO20:
plastic small outline package; 20 leads; body width 7.5 mm
SOT163-1
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
13
SSOP20:
plastic shrink small outline package; 20 leads; body width 4.4 mm
SOT266-1
Philips Semiconductors
Product specification
SA575
Low voltage compandor
1997 Nov 07
14
Philips Semiconductors and Philips Electronics North America Corporation reserve the right to make changes, without notice, in the products,
including circuits, standard cells, and/or software, described or contained herein in order to improve design and/or performance. Philips
Semiconductors assumes no responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright,
or mask work right to these products, and makes no representations or warranties that these products are free from patent, copyright, or mask
work right infringement, unless otherwise specified. Applications that are described herein for any of these products are for illustrative purposes
only. Philips Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing
or modification.
LIFE SUPPORT APPLICATIONS
Philips Semiconductors and Philips Electronics North America Corporation Products are not designed for use in life support appliances, devices,
or systems where malfunction of a Philips Semiconductors and Philips Electronics North America Corporation Product can reasonably be expected
to result in a personal injury. Philips Semiconductors and Philips Electronics North America Corporation customers using or selling Philips
Semiconductors and Philips Electronics North America Corporation Products for use in such applications do so at their own risk and agree to fully
indemnify Philips Semiconductors and Philips Electronics North America Corporation for any damages resulting from such improper use or sale.
This data sheet contains preliminary data, and supplementary data will be published at a later date. Philips
Semiconductors reserves the right to make changes at any time without notice in order to improve design
and supply the best possible product.
Philips Semiconductors
811 East Arques Avenue
P.O. Box 3409
Sunnyvale, California 940883409
Telephone 800-234-7381
DEFINITIONS
Data Sheet Identification
Product Status
Definition
Objective Specification
Preliminary Specification
Product Specification
Formative or in Design
Preproduction Product
Full Production
This data sheet contains the design target or goal specifications for product development. Specifications
may change in any manner without notice.
This data sheet contains Final Specifications. Philips Semiconductors reserves the right to make changes
at any time without notice, in order to improve design and supply the best possible product.
Copyright Philips Electronics North America Corporation 1997
All rights reserved. Printed in U.S.A.
Philips
Semiconductors
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