鈥?/div>
programmable parameters
- gain
- low pass filter
- high pass filter
- AGC threshold
- release time
- MPO
- receiver bias voltage
Principle features of the preamp are the input impedance
100 k鈩?and a gain of 14 dB.
The programmable filter block is composed of a low pass
and high pass filter which generates a range of high and
low pass corner frequencies. Although the control current
to this block varies linearly, linear to logarithmic conversion
is performed internally in order to adjust the corner frequencies
logarithmically. Both filters feature a 12 dB/octave rolloff
and unity gain.
The filters are followed by an AGC block. Up to 35 dB of
adjustable gain is provided as well as programmable
threshold and release time. The attack time of the AGC
block remains fixed and is independent of the release
time. The output current is driven into the preamp of the
clipper, thus, the AGC converts a voltage input into a
current output and is therefore, a transconductance block.
The next stage is an electronic MPO control peak 鈥渃lipper鈥?/div>
providing electronic clipping of the signal and setting of
the maximum output level. The clipper output is also a
transconductance block and drives a 40 k鈩?resistor (R
OUT 8
)
tied to the supply.
The input of the final stage is an inverting operational
amplifier. A feedback resistance of 240 k鈩?is provided
internally and this final stage is thus configured as a
voltage drive output stage. The DC bias current through
the receiver is also programmable.
鈥?/div>
on-chip voltage regulator
鈥?/div>
typical gain 60 dB
鈥?/div>
voltage drive output stage
鈥?/div>
telecoil preamp
STANDARD PACKAGING
鈥?/div>
Chip (136 x 110 mils)
Au Bump
CIRCUIT DESCRIPTION
The GP520A is a programmable analog signal path IC
designed for use in hearing instruments. The GP520A鈥檚
programmable parameters are adjusted by external
programming currents, such as generated by the GP521.
The GP520A provides a 2.5
碌A(chǔ)
reference current for use by
the GP521. Sixteen settings are possible in the GP521,
allowing the Programmable Current Sink (PCS) to sink
between 0 and 1.875 x
I
REF
.
The GP520A is composed of five functional blocks. The
input preamp, a filter block, the AGC block, MPO clipper
and the output stage.
V
CC
V
REG
9
13
VOLTAGE
REGULATOR
A
OUT
15
HPFB
18
HP
19
LPFB
22
BUFFER
IN
24
BUFFER
OUT
26
RECT.
IN
27
FULL WAVE
RECTIFIER
C
AGC
1
AVERAGING
CIRCUIT
THRESHOLD
DELTA
C
COMP
OUT B
IN
3
5
31
B
OUT
C
CLIP
7
30
V cc
R
+
LP
FILTER
R
OUT 8
AGC
VC AMP
CLIPPER
28
50k
29
A
IN
14
R
+
PREAMP
C
OUT
8
-
+
HP
2R
FILTER
R
IN14
-
40K
-
10
RF
D
IN
R
10K
LIN/LOG
CONVERTER
-
OUTPUT
+
LIN/LOG
CONVERTER
LIN/LOG
CONVERTER
11
D
OUT
I
REF
16
I
REF
25
I
REL
V
BIAS
23
I
GAIN
4
I
CLIP
17
I
BIAS
12
P GND
6
GND
20
I
HP
21
I
LP
2
I
THRESH
All resistors in ohms, all capacitors in farads unless otherwise stated.
FUNCTIONAL BLOCK DIAGRAM
Revision Date: May 1998
Document No. 510 - 78 - 06
GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 tel. +1 (905) 632-2996
Web Site: www.gennum.com E-mail: hipinfo@gennum.com
GP520A相關(guān)型號(hào)PDF文件下載
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