MITSUMI
IC for Headphone Stereos (bass boost) LAG668
IC for Headphone Stereos (bass boost)
Monolithic IC LAG 668
Outline
This IC was developed to provide bass boost functions without deviating from the basic design concept of
Mitsumi's LAG665, which is highly regarded for applications in headphone stereos for overseas markets in
particular.
Bass boost functions are widely adopted in models for overseas markets as well. However, because of
stringent cost constraints, there has been a need for an IC which is simple and inexpensive. This IC can
provide bass boost functions simply by adding three resistors and one capacitor (per channel).
Moreover, it has the same pinout as the LAG665, so that by making selective use of set features, a product
lineup can be developed without changes to the printed circuit board.
Features
1. Configuration: pre and power amps, motor control, E. VR, bass boost
2. Preamp off function convenient for use in models with radios
3. Independent motor control circuit
1. Motor noise is effectively suppressed
2. With motor on/off pin (motor can be stopped easily when radio is in use)
3. With fast forward pin
4. Bass boost frequency characteristic can be changed simply by changing the resistance multiplier.
5. Well-balanced E. VR circuit
1. L, R channels variable using a single VR
2. A-curve can be reproduced using B-curve VR
6. Few external components
Package
SOP-28B (LAG668F)
SDIP-30A (LAG668D)
Absolute Maximum Ratings
Item
Operating temperature
Storage temperature
Power supply current
Power consumption
Operating voltage
Symbol
T
OPR
T
STG
V
CC
max.
Pd
Vop
Ratings
-20~+65
-40~+125
-0.3~+7.5
DIP : 750, SOP : 450
+2.0~+5.0
Units
°
C
°
C
V
mW
V
MITSUMI
IC for Headphone Stereos (bass boost) LAG668
Electrical Characteristics
(Except where noted otherwise, Ta=25
°C
)
Min.
Typ. Max. Units
18
25
mA
72
42
0.6
0.05
150
22
10
10
0.2
66
0
200
100
36
20
30
20
31
38
0
28
0.5
30
1.0
37
3.0
3.0
500
0.72
0.80
0.05
0.01
0.01
38
0.5
0.05
0.02
5.6
33
2.0
2.0
6.0
5.0
40
3
dB
44
dB
Vrms
0.5
%
300 µVrms
kΩ
dB
-50
dB
kΩ
kΩ
Vrms
dB
dB
kΩ
kΩ
dB
dB
mW
mW
%
dB
mVrms
dB
mVrms
Item
Symbol
Measurement conditions
Consumption current
I
CC
V
IN
=0v, IM=0mA
°
C)
Preamp unit (Ta=25
Open-circuit gain
Gvo
V
O
=-10dBm, R
L
=infinite
Closed-circuit gain
Gvc
V
O
=-10dBm
Maximum output voltage
Vom
THD=10%
Total harmonic distortion ratio
THD
V
OUT
=400mVrms
Output noise voltage
Vno
V
IN
=0, Rg=2.2k, BPF (30~20kHz)
Input impedance
Z
IN
V
OUT
=-10dBm
Crosstalk between channels
C.T
Rg=2.2k, V
OUT
=-10dBm
Output voltage with pre off
Vooff
V
IN
=100mVrms
Output resistance with pre off
Rooff
Input resistance on pre off
Rioff
°
C)
Attenuator unit (Ta=25
Maximum input voltage
Vi max.
Maximum attenuation
Va max.
Vcont=min.
Attenuation error
Vaerr
Vcont=max.
Input impedance
Z
IN
Control pin input resistance
Zicot
°
C)
Power amp unit (Ta=25
Voltage gain
Gv
P
OUT
=5mW
Voltage gain difference
Gv
Vcont=max.
between channels
Maximum output power
I
Pom1
THD=10%, R
L
=32Ω
Maximum output power
II
Pom2
THD=10%, R
L
=16Ω
Total harmonic distortion ratio
THD
P
OUT
=5mW
Crosstalk between channels
C.T
P
OUT
=5mW
Output noise voltage
Vn
Rg=2.2k, Vcont=max.
Ripple rejection
RR
V
CC
=3V, 100Hz, 100mVp-p
Noise of preamp + power amp + B.B.
Vnto
V
IN
=0, Rg=2.2k, Vcont=max. 1
°
C)
Motor control unit (Ta=25
Consumption current
IMC
Startup current
IMS
Reference voltage
Vref
Between RML-ADJ pins
Reference voltage fluctuation
I
Vref1
V
CC
between 2.1 and 5.0 V
Reference voltage fluctuation
II
Vref2
I
M
between 25 and 250 mA
Reference voltage fluctuation
III
Vref3
Ta between -10 and 50
°
C
Current coefficient
K
Current coefficient fluctuation
I
K1
V
CC
between 2.1 and 5.0 V
Current coefficient fluctuation
II
K2
I
M
between 25 and 250 mA
Current coefficient fluctuation
III
K3
Ta between -10 and 50
°
C
Output voltage on forced on
VCEsa
I
M
=200mA, 14PIN=V
CC
Input resistance on forced on
Rion
Leakage current on forced off
IML
Input resistance on forced off
Ricon
Conditions unless stated otherwise
Amp unit: V
CC
=3.0V, f=1kHz, R
L
=16Ω, Pre OFF=OPEN
Motor unit: V
CC
=3.0V, I
M
=100mA, Motor unit: (Mitsumi model)
Note 1: Bass boost circuit constants are based on application circuit diagrams.
Note 2: Motor pin voltage fluctuations
40
0.45
18
30
*
32
mA
mA
0.87
V
%/V
%/mA
%/
°
C
43
%/V
%/mA
%/
°
C
0.6
V
kΩ
200
µA
kΩ
*
MITSUMI
IC for Headphone Stereos (bass boost) LAG668
Block Diagram
MITSUMI
IC for Headphone Stereos (bass boost) LAG668
Application Circuits
Bass Boost Power Amp Gain
Power amp gain (dB)
G
V
40
G
VH
35
30
25
G
VL
B
•
B Off
15
10
1
f1
G
V
: Power amp gain
G
VH
: Bass boost power amp gain
(high level)
G
VL
: Bass boost power amp gain
(low level, or boost off)
f1, f2: Cutoff frequencies
3dB
B
•
B ON
3dB
10
2
f2
10
3
10
4
10
5
10
6
Frequency (Hz)
G
VH
=G
V
+20Log
G
VL
=G
V
+20Log
f1=
f2=
R3
(
R1+R3
(
(dB)
(
R2//R3 R1
(
(dB)
R2//R3+ R1
(Hz)
1
2π ((R
1
//R
3
) +R
2
)C
1
2πR
2
C
(Hz)
MITSUMI
IC for Headphone Stereos (bass boost) LAG668
Characteristics
(Bass boost)
Recommended constants
Power amp gain
(dB)
40
35
30
25
20
15
10
1
R1=33kΩ
R2=4.7kΩ
G
VH
=37dB
G
VL
=20dB
R3=180kΩ f1=50Hz
C=0.1µF
f2=340Hz
No R4 or C2
10
2
10
3
10
4
10
5
10
6
Frequency (Hz)
Bass boost efficiency
Power amp gain
(dB)
40
35
30
25
20
15
10
1
10
2
10
3
10
4
10
5
10
6
R1=12kΩ
R2=2.2kΩ
R3=180kΩ
C=0.1µF
G
VH
=37dB
G
VL
=20dB
f1=130Hz
f2=720Hz
No R4 or C2
Frequency (Hz)
Response for poor headphone and cassette head characteristics
Power amp gain
(dB)
40
35
30
25
20
15
10
1
10
2
10
3
10
4
10
5
10
6
R1=33kΩ
R2=6.8kΩ
R3=180kΩ
C=0.1µF
G
VH
=37dB
G
VL
=23dB
f1=50Hz
f2=230Hz
No R4 or C2
Frequency (Hz)
Bass + treble boost
Power amp gain
(dB)
40
35
30
25
20
15
10
1
10
2
10
3
10
4
10
5
10
6
R1=33kΩ
R2=4.7kΩ
G
VH
=37dB
G
VL
=20dB
R3=180kΩ f1=50Hz
C=0.1µF
R4=20kΩ
C2=390pF
f2=340Hz
G
VH
=27dB
Frequency (Hz)
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