U4276B-FP [TEMIC]

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型号：	U4276B-FP
厂家：	TEMIC SEMICONDUCTORS
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U4276B

FM Multipath Noise Cancellation

Description

The U4276B is a bipolar integrated multipath noise cancellation circuit. It is designed for high performance car radio

applications.

Mute function controllable by microcomputer

Features

Suitable for analogue as well as digital processing

Only a few external components necessary

Preparation of the fieldstrength signal

Multipath noise cancellation

Block Diagram

BFSOUT

Buffer

Bandgap

FSIN

GND

Multipath

detection

Multipath

noise

cancellation

MPXOUT

AVFS

MPXIN

95 10619

MUTE

Pin Description

Symbol

AVFS

FSIN

Function

MUTE

BFSOUT

AVFS

Average of fieldstrength signal

Fieldstrength input

Ground

FSIN

GND

MPXIN Multiplex input signal

MPXOUT Multiplex output signal

Supply voltage

MPXOUT

MPXIN

BFSOUT Buffered fieldstrength output

MUTE External mute input

95 10632

TELEFUNKEN Semiconductors

1 (8)

Rev. A1, 05-Sep-96

Preliminary Information

U4276B

FSIN / BFSOUT

MPXIN / MPXOUT

V_S

50 k

MPXIN

40 A

BFSOUT

FSIN

50 k

94 8647

94 8649

All information about reception conditions is derived

from the fieldstrength signal. The fieldstrength signal at

FSIN is initially buffered so as not to impair the character-

istics of the IF IC and is available at BFSOUT.

60 k

MPXOUT

AVFS

200 A

60 k

40 A

94 8650

The MPX signal is fed directly from the FM demodulator

to input MPXIN and is available amplified by a factor of

1.5 at MPXOUT. The MPX signal is blanked out in the

event of multipath interference or when MUTE is acti-

vated externally in the circuit part MNC (Multipath Noise

Canceller). In all other cases, the MPX signal passes

through the IC unchanged.

AVFS

94 8648

The fieldstrength signal at buffer output BFSOUT is aver-

aged over time and applied to input AVFS via an RC

low-pass filter with a large time constant.

MUTE

94 8651

The function unit MNC can be controlled externally via

this pin. Blanking occurs when the voltage at the MUTE

pin falls below 1 V.

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TELEFUNKEN Semiconductors

Rev. A1, 05-Sep-96

Preliminary Information

U4276B

1. A linear characteristic, i.e. the output voltage must

be proportional to the logarithm of the IF voltage in

the range of RF levels encountered in practice. Devi-

ations from linearity lead to a different evaluation of

interference signals of the same intensity of the signal

levels are different.

Functional Description

Interference with FM reception can be triggered by vari-

ous causes, such as multipath reception, adjacent and

insufficient field strength. At the same time, multipath re-

ception is responsible for the most frequently occurring

types of interference.

2. The “signal level” output has to react to extremely

fast dips in the field strength. Total field strength fail-

ures lasting 500 ns and occuring a voltage dip to

approx. 0 V at the field strength output.

Acoustically relevant multipath interference, since it re-

quires a short reaction time, is suppressed directly by the

circuit via a Multipath Noise Cancellation (MNC) func-

tion.

Restrictions

The U4276B can be used both in conventional receivers

and in receivers with digital signal processing.

The field strength voltage becomes increasingly noisy in

the range of low RF levels (< 30 dB V). The noise pre-

vents reliable detection of interference. Therefore, only

The following demands are placed on the field strength the average field strength value can be evaluated over a

output of the IF amplifier: relatively large time constant in this range.

AF_left

MPX in

Digital or analogue

signal

MPX out

FM – tuner

U4276B

processing

AF_right

Fieldstrength

signal

Mute

System controller

95 10633

Figure 1. Block diagram

Multipath Noise Cancellation (MNC)

Extremely strong multipath interference remains audible

in spite of the monoblend function. The remaining inter-

ference is reduced still further by the MNC circuit if the

output MPXOUT is muted for a few microseconds while

the interference is still occuring (figure 2).

–

The average field strength must exceed a certain value

so that the noise in the field strength signal does not

cause the MNC to respond at low RF voltages

The MNC function can also be activated externally via

In order to eliminate the possibility of malfunctions, ac- the MUTE pin (low active). The circuit can therefore also

tivation of the MNC depends on the following condition: be used as a fast high performance mute stage.

TELEFUNKEN Semiconductors

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Rev. A1, 05-Sep-96

Preliminary Information

U4276B

94 8663

Figure 2.

In order to achieve best performance, the MNC-circuit Pin Mute (R2/R3, see figure 4) in the range of V/2 1 V.

has to be adapted well to the fieldstrength output of the The principle behaviour is shown in figure 3.

IF-IC. This can be done by adjustment of the DC-level at

95 10694

Field

strength

V_S

V_Mute

V_S

V_Mute

V_S

V_Mute

1.17 V

MNC activation level (AVFS)

RF level (dB V)

Figure 3.

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TELEFUNKEN Semiconductors

Rev. A1, 05-Sep-96

Preliminary Information

U4276B

95 10695

Mute

Figure 4.

Absolute Maximum Ratings

Reference point Pin 1b, unless otherwise specified

Parameters

Symbol

Value

Unit

Supply voltage

Supply current

Pin 6

t.b.d.

°C

Ambient temperature range

Storage temperature range

amb

– 30 to + 85

–55 to +150

125

stg

Junction temperature

Electrostatic handling (MIL standard 883 C)

ESD

2000

Thermal Resistance

Parameters

Symbol

Maximum

t.b.d.

Unit

K/W

Junction ambient

thJA

Electrical Characteristics

amb

= 25 C, V = 8.5 V, unless otherwise specified

Parameters

Test conditions / Pins

Symbol

Min.

Typ.

8.5

Max.

Unit

Supply voltage

Supply current

Fieldstrength

Input voltage

Output voltage

Pin 6

Pin 2

5.0

Pin 7

out

5000

load

Bandwidth

Pin 7

Pin 1

100

KHz

Input voltage

TELEFUNKEN Semiconductors

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Rev. A1, 05-Sep-96

Preliminary Information

U4276B

Parameters

Test conditions / Pins

Pin 4

Symbol

Min.

Typ.

0.06

Max.

Unit

Multipath Noise Cancellation

MPX input voltage

MPXIN

350

525

0.2

RMS

MPX output voltage

THD

R = 10 k

Pin 5

RMS

MPXOUT

R = 10 k

Pin 5

MPXIN

= 350 mV

Bandwidth

Mute-depth

Gain

R = 10 k

Pin 5

300

kHz

R = 10 k

3.5

Mute

Input voltage

low

high

Pin 8

MUTE

Application Circuit

100

4.7 F

C₃

BFSOUT

56 k

FSIN

GND

Buffer

Bandgap

47 k

MPXOUT

Multipath

detection

Multipath

noise

cancellation

AVFS

MPXIN

680 nF

95 10620

MUTE

56 k

100 nF

6 (8)

TELEFUNKEN Semiconductors

Rev. A1, 05-Sep-96

Preliminary Information

U4276B

Ordering Information

Extended type number

Package

Remarks

U4276B-AFP

SO8 plastic

U4276B-AFPG3

Taping according to IEC-286-3

Dimensions in mm

94 8862

TELEFUNKEN Semiconductors

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Rev. A1, 05-Sep-96

Preliminary Information

U4276B

Ozone Depleting Substances Policy Statement

It is the policy of TEMIC TELEFUNKEN microelectronic GmbH to

1. Meet all present and future national and international statutory requirements.

2. Regularly and continuously improve the performance of our products, processes, distribution and operating systems

with respect to their impact on the health and safety of our employees and the public, as well as their impact on

the environment.

It is particular concern to control or eliminate releases of those substances into the atmosphere which are known as

ozone depleting substances (ODSs).

The Montreal Protocol (1987) and its London Amendments (1990) intend to severely restrict the use of ODSs and

forbid their use within the next ten years. Various national and international initiatives are pressing for an earlier ban

on these substances.

TEMIC TELEFUNKEN microelectronic GmbH semiconductor division has been able to use its policy of

continuous improvements to eliminate the use of ODSs listed in the following documents.

1. Annex A, B and list of transitional substances of the Montreal Protocol and the London Amendments respectively

2. Class I and II ozone depleting substances in the Clean Air Act Amendments of 1990 by the Environmental

Protection Agency (EPA) in the USA

3. Council Decision 88/540/EEC and 91/690/EEC Annex A, B and C (transitional substances) respectively.

TEMIC can certify that our semiconductors are not manufactured with ozone depleting substances and do not contain

such substances.

We reserve the right to make changes to improve technical design and may do so without further notice.

Parameters can vary in different applications. All operating parameters must be validated for each customer

application by the customer. Should the buyer use TEMIC products for any unintended or unauthorized

application, the buyer shall indemnify TEMIC against all claims, costs, damages, and expenses, arising out of,

directly or indirectly, any claim of personal damage, injury or death associated with such unintended or

unauthorized use.

TEMIC TELEFUNKEN microelectronic GmbH, P.O.B. 3535, D-74025 Heilbronn, Germany

Telephone: 49 (0)7131 67 2831, Fax number: 49 (0)7131 67 2423

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TELEFUNKEN Semiconductors

Rev. A1, 05-Sep-96

Preliminary Information

U4276B-FP [TEMIC]

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