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 k

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.

RECTIFIER

VREG

265k

-A

VREG

A IN

B OUT

10k

A OUT

CB RECT IN

RECTCAP

GND

Adaptive Highpass Filter

with Independent Gain Block

FEATURES

ˇ unity gain 12 dB/oct. highpass Butterworth filter

ˇ adaptive frequency range from 200 Hz to 2 kHz

ˇ rectifier threshold set to 82 dBSPL (adjustable)

ˇ low noise, typically 2.6

ˇ 300

A typical current drain

ˇ operates from 1.1 to 3 VDC

ˇ preamplifier with 56 dB open loop gain

PACKAGING

ˇ 10 pin MICROpac

ˇ 10 pin PLIDŽ

ˇ 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

PARAMETER

VALUE

Supply Voltage

3 VDC

Power Dissipation

25 mW

Operating Temperature Range

-10

C to 40

Storage Temperature Range

-20

C to 70

A OUT

RECTCAP

RECTIN

VREG

A IN

GND

B OUT

CAUTION

CLASS 1 ESD SENSITIVITY

ABSOLUTE MAXIMUM RATINGS

PIN CONNECTIONS

PARAMETER

SYMBOL

CONDITIONS MIN TYP MAX UNITS

Total Current

165

300

450

Voltage Regulator (Pin 1)

REG

0.87

0.93

0.99

NFB 0.2 - 10kHz Filter fc set to 0.2kHz

2.6

at 12dB/oct Filter fc set to 2kHz

5.6

Attack Time

ATT

Release Time

STAGE A

Quiescent Voltage on pin 5

0.49

0.67

Open Loop Gain

Feedback Resistor

175

265

355

Current Sourcing Capacity

SOURCE

Current Sinking Capacity

SINK

FILTER SECTION

Quiescent Voltage on pin 3

0.49

0.58

0.67

Quiescent Voltage on pin 4

0.49

0.58

0.67

Quiescent Voltage on pin 8

0.55

0.78

Quiescent Voltage on pin 9

0.55

0.78

Filter Insertion Loss

FIL

OUT

= 850mV

RMS

f=2kHz (S1 closed)

-0.5

0.1

1.3

Distortion

THD

OUT

= 850mV

RMS

f=1kHz (S1 closed)

VAC 2 = 2.5mV

RMS

(S2 closed)

f = 100Hz (Note 1)

Rectifier Bandwidth

AC2

= 20mV

RMS

(S2 closed)

kHz

Pin 9 Nominal Current

VP9 = 0V

0.70

1.00

1.30

Current Range

RANGE

(Note 2, 3)

Slope

(Note 2, 4)

0.75

1.25

Rectifier Threshold

f = 100Hz (Note 2, 5)

1.7

2.5

2.8

Corner Frequency

(Note 2, 6)

140

200

260

RMS

Input Referred Noise

Rectifier Gain A

REC

IRN

All Conditions and Parameters remain as show in Test Circuit unless otherwise specified in CONDITIONS Column.

VQX

- 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:

AREC = 1.9375 x (VP4 / VP3) [VIN

= 10mVRMS] - 0.9375 x (VP4 / VP3) [VIN

= 18mVRMS]

ID0 = IP9

[VP9

= 0] ;

ID1 = IP9 [ VP4 = VQ4 + 35mV ; VP9

= 0]

ID2

IP9 [VP4 = VQ4 + 85mV ; VP9 = 0]; ID3 = IP9 [VP4 = VQ4 + 180mV ; VP9 = 0]

IRANGE = ID3 / ID0

SLOPE = (

(ID2

ID1 ) / 50mV ) x 14k

VAL = 85mV - ((ID2 - ID0) / SLOPE) x 14k

: VAH = 85mV + ( 50mV x ( ID3 - ID2

) / (

ID2 - ID1 ));

VP4

VAL [VIN

= 1.7mVRMS] and VP4

VAL [VIN

= 2.8mVRMS]

c = 1 / ( 2 x

x 1.41 x 10nF x R );

R = 26mV x (( 1 /

ID0

) + ( 1 / ( I2 -

ID0

)))

I2 = ((3 x (

ID0 + IP9[VP9

= VQ9

+ 18mV] )) / ( 4 - ((

ID0

IP9 [VP9 = VQ9 + 18mV] ) / ( ID0

IP9[VP9 = VQ9 - 18mV] )))

ELECTRICAL CHARACTERISTICS

Conditions: Supply Voltage V

= 1.3 V, Temperature 25

520 - 60 - 05

RECTIFIER

265k

-A

VIN

10k

VREG

8k4

83k5

LTC1001

82k

AC2

AC1

1 0 n

10n

V OUT

Fig. 1 Test Circuit

All resistors in ohms, all capacitors
in farads unless otherwise stated.

REGULATOR

BASE

CURRENT

COMP.

VIRTUAL

GROUND

265k

10k

13k5

56k

CONTROL

180

All resistors in ohms, all capacitors
in farads unless otherwise stated.

Fig. 2 Functional Schematic

RECTIFIER

VREG

265k

-A

10k

45k

10n

10k

100k

MIC

-A

-B

21k

GP509

GR581

Fig. 3 Typical Hearing Instrument Application

All resistors in ohms, all capacitors
in farads unless otherwise stated.

520 - 60 - 05

Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement.

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 a 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.

RECTIFIER

VREG

265k

-A

10k

45k

10n

10k

GR581

3k9

OUT

All resistors in ohms, all capacitors
in farads unless otherwise stated.

Fig. 4 Characterisation Circuit (used to generate typical curves)

-20

-30

-40

-50

-60

-70

OUTPUT LEVEL (dBV)

100

1000

10000

FREQUENCY (Hz)

Fig. 5 Frequency Response

REVISION NOTES

Changes to standard packaging information.

-43dBV

-48dBV

-53dBV

-58dBV

-63dBV

-68dBV

-73dBV

Part Number GR581