INTEGRATED CIRCUITS
DATA SHEET
TEA0678
Dual Dolby* B-type noise reduction
circuit, automatic music search,
with differential outputs and mute
Preliminary specification
Supersedes data of August 1993
File under Integrated Circuits, IC01
1996 Jun 06
Philips Semiconductors
Preliminary specification
Dual Dolby* B-type noise reduction circuit, automatic
music search, with differential outputs and mute
FEATURES
•
Dual noise reduction (NR) channels
•
Head pre-amplifiers
•
Reverse head switching
•
Automatic Music Search (AMS)
•
Mute position
•
Equalization with electronically switched time constants
•
Dolby reference level = 387.5 mV
•
32 pins
•
Switch inputs TTL compatible
•
Differential output stage has:
– Capability to drive 1.2 nF capacitive load
– Capability to drive 1 kΩ load
– Short-circuit proof
– Short-circuit proof to 16 V via coupling capacitor.
•
Improved EMC behaviour.
GENERAL DESCRIPTION
TEA0678
The TEA0678 is a bipolar integrated circuit that provides
two channels of Dolby B noise reduction for playback
applications in car radios. It includes head and
equalization amplifiers with electronically switchable time
constants. Furthermore it includes electronically
switchable inputs for tape drivers with reverse heads.
This device also detects pauses of music in Automatic
Music Search (AMS) mode, with a delay time fixed
externally by a resistor. The short-circuit proof output
stage of the TEA0678 is differential and provides muting.
The device will operate with power supplies in the range of
7.6 to 12 V, output overload level increasing with increase
in supply voltage. Current drain varies with supply voltage,
noise reduction on/off and AMS on/off so it is advisable to
use a regulated power supply or a supply with a long time
constant.
.Current drain varies with these variables:
Supply voltage
Noise reduction on/off
AMS on/off.
Because of this current drain variation it is advisable to use
a regulated power supply or a supply with a long time
constant.
QUICK REFERENCE DATA
SYMBOL
V
CC
I
CC
S
+
N
-------------
-
N
supply voltage
supply current
signal plus noise-to-noise ratio
PARAMETER
−
78
MIN.
7.6
TYP.
10
25
84
MAX.
12
28
−
UNIT
V
mA
dB
ORDERING INFORMATION
TYPE
NUMBER
TEA0678
TEA0678T
PACKAGE
NAME
SDIP32
SO32
DESCRIPTION
plastic shrink dual in-line package; 32 leads (400 mil)
plastic small outline package; 32 leads; body width 7.5 mm
VERSION
SOT232-1
SOT287-1
Remark Dolby*:
Available only to licensees of Dolby Laboratories Licensing Corporation, San Francisco, CA94111,
USA, from whom licensing and application information must be obtained. Dolby is a registered trade-mark of Dolby
Laboratories Licensing Corporation.
1996 Jun 06
2
1996 Jun 06
Vref
24
kΩ
180
Ω
330
kΩ
1 kΩ
10
nF
8.2
kΩ
470
pF
470
pF
EQ switch from
microprocessor
LOW: 120
µs
OPEN: 70
µs
10
µF
AMSout
100
nF
18
kΩ
15 nF
26
24
22
19
20
25
23
21
18
17
270 kΩ
27
180 kΩ
LOW: INPUT 1
HIGH: INPUT 2
from
microprocessor
head switch
input
4.7 nF
BLOCK DIAGRAM
handbook, full pagewidth
LOW: MUTE ON
HIGH: MUTE OFF
from
microprocessor
Philips Semiconductors
RL RL
27
kΩ
10
µF
output
B−
CL
output
B+
1
µF
330
nF
4.7
µF
4.7
µF
32
31
30
29
28
EQ
AMP.
DOLBY B NR CIRCUIT
PRE
AMP.
15
kΩ
EQ
DELAY
TIME
VCC
LEVEL
DETECTOR
GND
POWER
SUPPLY
AMS
AMS
PROCESSOR
TEA0678
LOGIC
Vref
Dual Dolby* B-type noise reduction circuit, automatic
music search, with differential outputs and mute
3
DOLBY B NR CIRCUIT
EQ
AMP.
6
7
15 nF
180 kΩ
4.7 nF
Rt
24
kΩ
Vref
270 kΩ
100
nF
8
9
10
11
12
13
VCC
8.2
kΩ
10
nF
AMS
delay
time
330
kΩ
1 kΩ
180
Ω
10
µF
MUTE NR
15
kΩ
HEAD-
SWITCH
PRE
AMP.
1
2
3
4
5
14
15
16
4.7
µF
4.7
µF
output
A−
CL
output
A+
1
µF
330
nF
100
µF
RL RL
from
microprocessor
470
pF
470
pF
LOW: NR ON
OPEN: OFF
HIGH: AMS ON
MED769
Preliminary specification
TEA0678
Fig.1 Block and application diagram.
Philips Semiconductors
Preliminary specification
Dual Dolby* B-type noise reduction circuit, automatic
music search, with differential outputs and mute
PINNING
SYMBOL
OUTA−
OUTA+
NR/AMS
INCA
OUTCA
INTA
CONTRA
HPA
SCA
TD
EQA
EQFA
V
CC
INA1
V
ref
INA2
INB2
HS
INB1
GND
EQFB
EQB
AMSEQ
SCB
HPB
CONTRB
INTB
OUTCB
INCB
MUTE
OUTB+
OUTB−
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
DESCRIPTION
negative output channel A
positive output channel A
noise reduction/music search switch
input mute/output stage channel A
output Dolby B processor channel A
integrating filter channel A
control voltage channel A
high-pass filter channel A
side chain channel A
delay time constant
equalizing output channel A
equalizing feedback channel A
supply voltage
input channel A1 (forward or reverse)
reference voltage
input channel A2 (reverse or forward)
input channel B2 (reverse or forward)
head switch input
input channel B1 (forward or reverse)
ground
equalizing feedback channel B
equalizing output channel B
AMS output and EQ switch input
side chain channel B
high-pass filter channel B
control voltage channel B
integrating filter channel B
output Dolby B processor channel B
input mute/output stage channel B
mute switch
positive output channel B
negative output channel B
Fig.2 Pin configuration.
EQFA 12
VCC 13
INA1 14
Vref 15
INA2 16
MED770
TEA0678
handbook, halfpage
OUTA−
OUTA+
NR/AMS
INCA
OUTCA
INTA
CONTRA
HPA
SCA
1
2
3
4
5
6
7
8
32 OUTB−
31 OUTB+
30 MUTE
29 INCB
28 OUTCB
27 INTB
26 CONTRB
25 HPB
TEA0678
9
24 SCB
23 AMSEQ
22 EQB
21 EQFB
20 GND
19 INB1
18 HS
17 INB2
TD 10
EQA 11
1996 Jun 06
4
Philips Semiconductors
Preliminary specification
Dual Dolby* B-type noise reduction circuit, automatic
music search, with differential outputs and mute
FUNCTIONAL DESCRIPTION
Noise Reduction (NR)
is enabled when pin NR/AMS is
connected to ground and disabled when open-circuit (left
floating from a 3-state output).
Dolby noise reduction only operates correctly if 0 dB Dolby
level is adjusted at 387.5 mV.
Automatic Music Search (AMS)
is enabled when pin
NR/AMS is connected to HIGH (5 V) and disabled when
open-circuit (left floating from a 3-state output). In AMS
mode the signal of both channels are rectified and then
added. This means, even if one channel signal appears
inverted to the other channel, with the TEA0678 the normal
AMS function is ensured (see Figs 4, 5 and 6).
Equalization time constant switching
(70
µs
or 120
µs)
is achieved when pin AMSEQ is connected to GND via an
18 kΩ resistor (120
µs),
or left open-circuit (70
µs).
This does not affect the AMS output signal during AMS
mode (see Fig.1).
TEA0678
Head switching
is achieved when pin HS is connected to
GND (input IN1 active) or connected to HIGH (5 V) level
(input IN2 active). If left open-circuit IN1 is active.
Mute
is enabled when pin MUTE is connected to ground
and off when connected to HIGH (5 V) level. For smooth
switching a time constant is recommended. If left
open-circuit MUTE is active.
The
differential output stage
of each channel is
connected via a provision to the Dolby and pre-amplifier
part. This provision may be used for any processing of the
tape signal or to add another signal. Each output drives a
resistive load of nominal 10 kΩ and is capable of driving
1 kΩ, also a capacitive load of 1.2 nF to ground and
between differential outputs. Each output can be
short-circuited to a battery (16 V) via a coupling capacitor
(4.7
µF).
LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 134); note1.
SYMBOL
V
CC
V
i
supply voltage
input voltage (pins 1 to 32) except pin 15 (V
ref
); pin 3
(NR/AMS), pin 18 (HS) and pin 30 (MUTE) to V
CC
input voltage at pin 3 (NR/AMS), pin 18 (HS) and
pin 30 (MUTE)
t
short
T
stg
T
amb
V
es
pin 15 (V
ref
) to V
CC
short-circuiting duration
storage temperature
operating ambient temperature
electrostatic handling voltage for all pins
note 3
note 4
Notes
1. The device may not operate correctly when subjected to these ratings when the ratings exceed the electrical
characteristics of the device as specified in Chapter “Characteristics”. The device will recover automatically when the
environment is reduced to the requirements of the characteristics.
2. The TEA0678 allows a HIGH-level at switching pins without supply voltage (V
CC
= 0; stand-by mode). This means a
maximum input voltage of 6.5 V for the switching input pins.
3. Human body model (1.5 kΩ, 100 pF).
4. Machine model (0
Ω,
200 pF).
note 2
PARAMETER
CONDITIONS
0
−0.3
−0.3
−
−55
−40
−2
−500
MIN.
MAX.
16
+V
CC
+6.5
5
+150
+85
+2
+500
V
V
V
s
°C
°C
kV
V
UNIT
1996 Jun 06
5
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