Gennum Corporation GR581 Datasheet
DESCRIPTION
The GR581 is a level-sensitive, adaptive highpass filter
comprised of a current controlled highpass filter, a half- wave
rectifier, a voltage regulator for microphone bias and a separate
preamplifier.
The internal rectifier senses the long term average signal level
and controls the filter response by setting the control current
of the filter. The rectifier sensitivity, with respect to the input
signal, can be increased by placing the internal preamplifier
(A) before the filter section of the GR581. The preamplifier has
an internal 265 kΩ feedback resistor from its input to output, to
facilitate in setting the gain.
An increase of 20 dB above the rectifier threshold will
automatically increase the corner frequency one decade
above the initial corner frequency. The filter will only allow an
increase in corner frequency of one decade, regardless of
further increases in the input signal level.
It is recommended that the attack and release times be set to
30 ms and 90 ms respectively. The average time period of a
speech frame is about 15 ms which is not long enough to
activate the filter, however long term average noise, which can
have time periods greater than 30 ms, will activate the filter
(providing that the amplitude is above the rectifier threshold).
The GR581 is an improved version of the LS581adaptive high
pass filter and has an identical pinout.
GR581 DATA SHEET
All resistors in ohms, all capacitors
in farads unless otherwise stated.
5 98374
RECTIFIER
VREG
10
2
1
6
265k
-A
+
-
B
V
REG
A IN
B OUT
10k
V
B
A OUT
CAC
B
RECT IN
RECT
CAP
GND
Adaptive Highpass Filter
with Independent Gain Block
FEATURES
• unity gain 12 dB/oct. highpass Butterworth filter
• adaptive frequency range from 200 Hz to 2 kHz
• rectifier threshold set to 82 dBSPL (adjustable)
• low noise, typically 2.6
µV
• 300 µA typical current drain
• operates from 1.1 to 3 VDC
• preamplifier with 56 dB open loop gain
PACKAGING
• 10 pin MICROpac
• 10 pin PLID
®
• Chip (73 x 59 mils)
FUNCTIONAL BLOCK DIAGRAM
Document No. 520 - 60 - 05
Revision Date: January 2001
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-2814
Gennum Japan Corporation: C-101, Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168-0081, Japan tel. (03) 3334-7700 fax:(03) 3247-8839
520 - 60 - 05
2
PARAMETER VALUE
Supply Voltage 3 VDC
Power Dissipation 25 mW
Operating Temperature Range -10°C to 40°C
Storage Temperature Range -20°C to 70°C
A OUT
RECT
CAP
RECT
IN
V
B
V
REG
A IN
GND
C
B
B OUT
C
A
CAUTION
CLASS 1 ESD SENSITIVITY
ABSOLUTE MAXIMUM RATINGS
PIN CONNECTIONS
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Total Current I
T
165 300 450 µA
Voltage Regulator (Pin 1) V
REG
0.87 0.93 0.99 V
DC
NFB 0.2 - 10kHz Filter fc set to 0.2kHz - 2.6 -
at 12dB/oct Filter fc set to 2kHz - 5.6 -
Attack Time t
ATT
-30 -ms
Release Time t
RE
L
-90 -ms
STAGE A
Quiescent Voltage on pin 5 V
Q5
0.49 - 0.67 V
DC
Open Loop Gain A
OL
45 56 - dB
Feedback Resistor R
F
175 265 355 kΩ
Current Sourcing Capacity I
SOURCE
15 30 - µA
Current Sinking Capacity I
SINK
15 30 - µA
FILTER SECTION
Quiescent Voltage on pin 3 V
Q3
0.49 0.58 0.67 V
DC
Quiescent Voltage on pin 4 V
Q4
0.49 0.58 0.67 V
DC
Quiescent Voltage on pin 8 V
Q8
0.55 - 0.78 V
DC
Quiescent Voltage on pin 9 V
Q9
0.55 - 0.78 V
DC
Filter Insertion Loss FIL V
OUT
= 850mVRMS f=2kHz (S1 closed) -0.5 0.1 1.3 dB
Distortion THD V
OUT
= 850mVRMS f=1kHz (S1 closed) - 2 3 %
V
AC 2
= 2.5mVRMS (S2 closed) 5 7 9
f = 100Hz (Note 1)
Rectifier Bandwidth B
R
V
AC2
= 20mVRMS (S2 closed) - 4 - kHz
Pin 9 Nominal Current I
P9
VP9 = 0V 0.70 1.00 1.30 µA
Current Range I
RANGE
(Note 2, 3) 8 10 12
Slope (Note 2, 4) 0.75 1 1.25
Rectifier Threshold V
TH
f = 100Hz (Note 2, 5) 1.7 2.5 2.8 mV
DC
Corner Frequency f
c
(Note 2, 6) 140 200 260 Hz
µVRMS
Input Referred Noise
Rectifier Gain A
REC
IRN
All Conditions and Parameters remain as show in Test Circuit unless otherwise specified in CONDITIONS Column.
V
QX
- quiescent (unbias) voltage measured on the pin, (nothing connected to the pin). VPX - actual voltage measured on the pin at given condition ( X is pin number).
NOTES: 1. A
REC
= 1.9375 x (VP4 / VP3) [V
IN
= 10mV
RMS
] - 0.9375 x (VP4 / VP3) [V
IN
= 18mV
RMS
]
2. I
D0
= I
P9
[VP9 = 0] ; I
D1
= I
P9
[ VP4 = VQ4 + 35mV ; V
P9
= 0]
I
D2
= IP9 [VP4 = VQ4 + 85mV ; VP9 = 0]; ID3 = IP9 [VP4 = VQ4 + 180mV ; VP9 = 0]
3. I
RANGE
= ID3 / I
D0
4. SLOPE = ((I
D2
- ID1 ) / 50mV ) x 14kΩ
5. V
AL
= 85mV - ((ID2 - ID0) / SLOPE) x 14kΩ: VAH = 85mV + ( 50mV x ( ID3 - I
D2
) / ( I
D2
- I
D1
));
V
P4 ≤ VAL
[V
IN
= 1.7mV
RMS
] and V
P4 ≥ VAL
[V
IN
= 2.8mV
RMS
]
6.
ƒ
c
= 1 / ( 2 x π x 1.41 x 10nF x R ); R = 26mV x (( 1 / I
D0
) + ( 1 / ( I2 - I
D0
)))
I2 = ((3 x ( I
D0
+ IP9[V
P9
= VQ9 + 18mV] )) / ( 4 - (( ID0 + I
P9
[VP9 = VQ9 + 18mV] ) / ( I
D0
+ I
P9[VP9
= VQ9 - 18mV] )))
ELECTRICAL CHARACTERISTICS Conditions: Supply Voltage V
CC
= 1.3 V, Temperature 25oC
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