SA572 Philips, SA572 Datasheet - Page 4

• Manufacturer Part Number: SA572
• Description: Programmable analog compandor
• Manufacturer: Philips

Philips Semiconductors
TEST CIRCUIT
AUDIO SIGNAL PROCESSING IC COMBINES VCA
AND FAST ATTACK/SLOW RECOVERY LEVEL
SENSOR
In high-performance audio gain control applications, it is desirable to
independently control the attack and recovery time of the gain
control signal. This is true, for example, in compandor applications
for noise reduction. In high end systems the input signal is usually
split into two or more frequency bands to optimize the dynamic
behavior for each band. This reduces low frequency distortion due
to control signal ripple, phase distortion, high frequency channel
overload and noise modulation. Because of the expense in
hardware, multiple band signal processing up to now was limited to
professional audio applications.
With the introduction of the Signetics SA572 this high-performance
noise reduction concept becomes feasible for consumer hi fi
applications. The SA572 is a dual channel gain control IC. Each
channel has a linearized, temperature-compensated gain cell and an
improved level sensor. In conjunction with an external low noise op
1998 Nov 03
Programmable analog compandor
V
2
V
1
2.2 F
1%
R
= 10 F
2.2 F
2
3.3k
5
(3,13)
(7,9)
(2,14)
(4,12)
6.8k
RECTIFIER
G
BUFFER
Figure 3. Test Circuit
(8)
(1,15)
(16)
(6,10)
(5,11)
4
1k
82k
amp for current-to-voltage conversion, the VCA features low
distortion, low noise and wide dynamic range.
The novel level sensor which provides gain control current for the
VCA gives lower gain control ripple and independent control of fast
attack, slow recovery dynamic response. An attack capacitor C
with an internal 10k resistor R
recovery time t
C
the high-frequency spectrum and 40ms for the low frequency band
can be obtained with 0.1 F and 1.0 F attack capacitors,
respectively. Recovery time of 200ms can be obtained with a 4.7 F
recovery capacitor for a 100Hz signal, the third harmonic distortion
is improved by more than 10dB over the simple RC ripple filter with
a single 1.0 F attack and recovery capacitor, while the attack time
remains the same.
The SA572 is assembled in a standard 16-pin dual in-line plastic
package and in oversized SOL package. It operates over a wide
supply range from 6V to 22V. Supply current is less than 6mA. The
SA572 is designed for applications from –40 C to +85 C.
R
and an internal 10k resistor R
+
2.2k
2.2 F
270pF
17.3k
R
1%
R
3
of a tone burst is defined by a recovery capacitor
+
–
.1 F
NE5234
1 F
A
defines the attack time t
R
. Typical attack time of 4ms for
+
+
22 F
22 F
100
Product specification
+15V
V
0
SR00696
SA572
A
–15V
. The
A