Patented 1985 Patent Pending Europe 83.300836.0
Canada 1183580 USA 4506169 Japan 58-06886
BLOCK DIAGRAM
Low Distortion AGC
Compression Amplifier
LP502 CUSTOM DATA SHEET
adjustable gain from 0 to 60 dB
0.94 V DC voltage regulator on-chip
attack time fixed at less than 1 ms
release time adjustable from 40 to 500 ms
low input referred noise 1.2
V
<1 % distortion at 10 mV
RMS
output
operates from 1.05 to 3 V
DC
STANDARD PACKAGING
8 pin MICROpac
8 pin PLID
Chip (64 x 62 mils)
Au Bump
FEATURES
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Gennum Japan Corporation:C-101 Mi yamae Vill age, 21042 Mi yamae, Suginamiku, Tokyo
168-0081
, Japan tel. (03) 3334-7700 fax (03) 3247-8839
Document No. HP2802-1
DESCRIPTION
The LP502 is a compression (AGC) preamplifier that consists
of a single-ended input inverting amplifier, with an internal
current controlled resistance connected between input and
output.
By using R
GT
(see test circuit) to vary the value of this current
controlled resistance, the amplifier gain and compression
threshold can be controlled over a range of 60 dB.
The AGC current is derived from a full wave rectifier driven by
a differential amplifier. The attack time of the AGC circuit is
fixed at less than 1 ms. The release time is adjustable from
40 to 500 ms by selecting the value of an external capacitor
(C3).
Internally, a series shunt voltage regulator produces a 0.94 V
DC regulated output voltage. This provides a bias for electret
microphones and permits circuit operations over a wide range
of supply voltages, 1.05 to 3 V
DC
for LP502 without any
degradation of electrical performances.
As compared to the LD502, the LP502 incorporates an
additional diode between the amplifier output and the AGC
filter point. This "attack diode" is responsible for precharging
the AGC filter point, which enables quicker attack time and
helps to reduce the gain overshoot (during transients) that is
observed in the LD502 with certain combinations of AGC input
coupling and filter capacitors. However, with this diode
connected, some level of AGC is always present with higher
output levels even when the AGC input is disconnected.
Therefore the LP502 cannot be used as a "pure" linear
amplifier.
GAIN SET
A OUT
AGC IN
AGC FILTER
GND
A IN
V
REG
V
B
VOLTAGE
REGULATOR
AMPLIFIER
FULL WAVE
RECTIFIER
8
5
6
3
4
7
2
1
2
HP2802-1
ABSOLUTE MAXIMUM RATINGS
PARAMETER
VALUE/UNITS
Supply Voltage
3 V DC
Power Dissipation
25 mW
Operating Temperature Range
-10
C to 50
C
Storage Temperature Range
-20
C to 70
C
CAUTION
CLASS 1 ESD SENSITIVITY
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Gain
A
V
V
OUT
= 11.0 mV,
38
41
46
dB
Output Level
V
OHIGH
V
IN
= 6.32 mV, S1 closed
7.5
12
15.5
mV
Distortion -Linear
THD
V
OUT
= 11.0 mV
-
1
2.9
%
- AGC
V
IN
= 6.32mV, S1 closed
-
1
2.2
%
Input Referred Noise
IRN
S2 closed,NFB 0.2 to 10 kHz at 12 dB/Oct
-
1.2
2.2
V
Compression Function Ratio
V
IN
= 0.1 to 6.32 mV, S1 closed
2
5
8
dB
Total Amplifier Current
I
AMP
160
310
380
A
Regulated Voltage
V
REG
0.890
0.940
0.990
VDC
Supply Rejection
PSRR
51
60
-
dB
ELECTRICAL CHARACTERISTICS
Conditions: Frequency = 1 kHz, Temperature = 25
C, Supply Voltage V
B
= 1.3 VDC
PIN CONNECTION
1
4
5
8
AGC FILTER
AGC IN
V
B
GND
GAIN SET
A OUT
V
REG
20 Log ( )
V
OUT
V
IN
All parameters and switches remain as shown in Test Circuit unless otherwise stated in "Conditions" column
Fig. 1 Test Circuit
All resistors in ohms, all capacitors in microfarads unless otherwise stated
A IN
VOLTAGE
REGULATOR
AMP
FULL WAVE
RECTIFIER
C2
1.0
R
M
33K
V
IN
R
S
= 3.5k
C1
0.47
S2
R
GT
130k
C3
1.0
C4
0.1
S1
R
L
10K
V
OUT
V
B
= 1.3 VDC
I
TOT
7
2
1
8
5
6
3
4
R
TH
0
C5
1.0
3
HP2802-1
All resistors in ohms, all capacitors in microfarads unless otherwise stated
Fig. 2 LP502/LC549Hearing Instrument Application
All resistors in ohms, all capacitors in
microfarads unless otherwise stated
Fig. 3 LP502/LE507 Hearing Instrument Application
0.1
4.7
R
S
3.9k
FULL WAVE
RECTIFIER
500k
0.1-1.0
0.1
4.7
V
C
4.7
V
B
=1.3 VDC
LP502
2
1
7
4
3
6
5
8
NC
0.047
R
L
=400
TYP
2
3
7
5
6
1
8
AMP
LC549
4
VOLTAGE
REGULATOR
0.1
GAIN TRIM
=10k
0.1
4.7
R
S
3.9k
500k
0.47
0.1
0.1
0.1
BK1606
V
B
=1.3 VDC
LP502
2
1
7
4
3
6
5
8
R
E
=33
V
C
10k
AMP
7
1
4
3
2
8
6
25k
5
FULL WAVE
RECTIFIER
2k
18k
13.5k
LE507
GAIN TRIM
33k
VOLTAGE
REGULATOR
Z=1k
4
HP2802-1
Fig. 8 Total Harmonic Distortion
vs Output Level
4.0
3.0
2.0
1.0
0.0
0.0
5.0
10.0
15.0
20.0
25.0
OUTPUT (mV)
THD (%)
100
0.01
0.1
1.0
10
INPUT (mV)
Fig. 5 I/O Characteristics at
Various R
GT
Values
0.1
1
10
R
GT
=130k
R
GT
=82k
R
GT
=47k
100
0.01
0.1
1.0
10
INPUT (mV)
Fig. 6 Effects of Supply Voltage
Variation
0.1
10
V
B
=3 VDC
V
B
=1.3 VDC
Fig. 7 Frequency Response at
Various C
S
Values
OUTPUT (mV)
100
10
1
0.01
0.1
1.0
10
INPUT (mV)
Fig. 4 I/O Characteristics at
Various R
TH
Values
R
TH
=0k
R
TH
=10k
R
TH
=22k
R
TH
=50k
4
2
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
C
S
=0.1
F
C
S
=0.22
F
C
S
=0.047
F
C
S
=0.033
F
20 200 2K
20k
FREQUENCY (Hz)
RELATIVE OUTPUT (dB)
OUTPUT (mV)
OUTPUT (mV)
R
TH
=0
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.
Copyright August 1997 Gennum Corporation. All rights reserved. Printed in Canada.
DOCUMENT
IDENTIFICATION
PRODUCT PROPOSAL
This data has been compiled for market investigation purposes
only, and does not constitute an offer for sale.
ADVANCE INFORMATION NOTE
This product is in development phase and specifications are
subject to change without notice. Gennum reserves the right to
remove the product at any time. Listing the product does not
constitute an offer for sale.
PRELIMINARY DATA SHEET
The product is in a preproduction phase and specifications are
subject to change without notice.
DATA SHEET
The product is in production. Gennum reserves the right to make
changes at any time to improve reliability, function or design, in
order to provide the best product possible.
R
GT
=68k
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