NJRC NJU8755V Analog signal input stereo class d power amplifier Datasheet

NJU8755
PRELIMINARY
Analog Signal Input Stereo Class D Power Amplifier
! PACKAGE OUTLINE
! GENERAL DESCRIPTION
The NJU8755 is an analog signal input stereo class D
power amplifier. The NJU8755 includes Inversion
operational amplifier input circuit, PWM modulators, an
output-short protector and a low voltage detector. The
NJU8755 incorporates BTL amplifiers, which eliminate
AC coupling capacitors, capable of driving up to
1.2W/channel with simple external LC low-pass filters.
Class-D operation achieves high power-efficiency,
which achieves longer battery life for battery powered
applications, thus the NJU8755 is suited for portable
audio, note-PC, etc.
NJU8755V
! PIN CONFIGURATION
! FEATURES
2-Channel Analog Signal Input
VDD
2-Channel BTL Outputs :1.2W/channel at 5V into 8Ohms
INL
Standby(Hi-Z), Mute Control
TEST
Built-in Short Protector
MUTE
Built-in Low Voltage Detector
VDDL
Operating Voltage
2.7 ~ 5.25V
OUTLP
CMOS Technology
VSSL
Package Outline
SSOP20
OUTLN
VDDL
V
DDL
! BLOCK DIAGRAM
VDD
VSS
#
#
#
#
#
#
#
#
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
VSS
INR
COM
STBY
VDDR
OUTRP
VSSR
OUTRN
VDDR
VDDR
VDDL
INL
OUTLP
+
-
VSSL
Pulse
Width
Modulator
VDDL
OUTLN
+
VSSL
COM
VDDR
+
+
INR
OUTRP
Pulse
Width
Modulator
VSSR
VDDR
-
OUTRN
VSSR
Short
Protector
Soft Start
Control
MUTE
Ver.2003-03-12
STBY
Logic
Low Voltage
Detector
TEST
-1-
NJU8755
! PIN DESCRIPTION
No.
1
2
SYMBOL
VDD
INL
I/O
−
I
3
TEST
I
4
MUTE
I
VDDL
−
L-channel Power Supply : VDDL=5.0V
OUTLP
VSSL
OUTLN
O
−
O
L-channel positive output
L-channel Power GND
L-channel negative output
VDDR
−
R-channel Power Supply : VDDR=5.0V
OUTRN
VSSR
OUTRP
O
−
O
5
9
10
6
7
8
11
12
16
13
14
15
FUNCTION
Power Supply : VDD=5.0V
L-channel signal input
Maker test
This pin must be connected to GND.
Mute control
Low : Mute ON High : Mute OFF
R-channel negative output
R-channel Power GND : VSSR=0V
R-channel positive output
Standby control
17
STBY
I
Low : Standby ON High : Standby OFF
18
COM
−
Analog common
19
INR
I
R-channel signal input
20
VSS
−
Power GND : VSS=0V
*The relations of ”VSS= VSSL= VSSR=0V” and “VDD= VDDL=VDDR” must be maintained.
*Pin No.4(MUTE) and 17(STBY) must be connected to VDD, when these pins are not used.
-2-
Ver.2003-03-12
NJU8755
NJU3555
! FUNCTIONAL DESCRIPTION
(1) Signal Output
The OUTLP/LN and OUTRP/RN generate respectively L-channel and R-channel PWM output signals, which will
be converted to analog signal via external 2nd-order or higher LC filter. A switching regulator with a high
response against a voltage fluctuation is the best selection for the VDDL and VDDR, which are the power supply for
output drivers. To obtain better THD performance, the stabilization of the power is required.
(2) Standby
By setting the STBY pin to “L”, the standby mode is enabled. In the standby mode, the entire functions of the
NJU8755 enter a low-power state, and the output pins(OUTLP/LN and OUTRP/RN) are high impedance.
(3) Mute
By setting the MUTE pin to “L”, the Mute function is enabled. In the Mute mode, the output pins(OUTLP/LN and
OUTRP/RN) output square wave(Duty: 50%).
(4) Low Voltage Detector
When the power supply voltage drops down to below VDD(MIN), the internal oscillation is halted for prevention
to generate unwanted frequency, and the output pins(OUTLP/LN and OUTRP/RN) become in high impedance.
(5) Short Circuit Protection
The short protector, which protects the NJU8755 against high short-circuit current, turns off the output drivers
of L-channel and R-channel independently. After about 5 seconds from the protection, the NJU8755 returns to
normal operation. The short protector functions at following accidents.
• Short
• Short
• Short
• Short
• Short
• Short
between OUTLP and OUTLN
between OUTLP and VSSL
between OUTLN and VSSL
between OUTRP and OUTRN
between OUTRP and VSSR
between OUTRN and VSSR
Note 1)
The detectable current and the period for the protection depend on the power supply voltage and
ambient temperature.
Note 2) The short protector is not effective for a long term short-circuit but for an instantaneous accident.
Continuous high-current may cause permanent damage to NJU8755.
Ver.2003-03-12
-3-
NJU8755
! ABSOLUTE MAXIMUM RATINGS
(Ta=25°C)
PARAMETER
Supply Voltage
Input Voltage
Operating Temperature
Storage Temperature
Power Dissipation
SYMBOL
VDD
VDDL
VDDR
Vin
Topr
Tstg
PD
RATING
-0.3 ~ +5.5
-0.3 ~ +5.5
-0.3 ~ +5.5
-0.3 ~ VDD+0.3
-40 ~ +85
-40 ~ +125
300 (SSOP20)
UNIT
V
V
V
V
°C
°C
mW
Note 1) All voltage are relative to “VSS= VSSL= VSSR=0V” reference.
Note 2) The LSI must be used inside of the “Absolute maximum ratings”. Otherwise, a stress may cause
permanent damage to the LSI.
Note 3) De-coupling capacitors for VDD-VSS, VDDL-VSSL , and VDDR-VSSR should be connected for stable operation.
Note 4) Power Dissipation
The class-D amplifiers are more power efficiency, and dissipate power less than general
analog-amplifiers. In theory, the NJU8755 actualize quite high output-power such as 1.2W/channel at 5V
operation with 8ohms load, and total power is supposed to be 2.4W. For this reason, it looks as if the
NJU8755 exceeds the absolute maximum rating of the power dissipation. However, in practice, the
effective output-power of usual music sound is only about 1/10 of its maximum output power, thus it may
never exceed the absolute maximum rating.
The maximum power dissipation in the system is calculated, as shown below.
Pdmax(W) = (Tjmax(°C) - Ta(°C)) /θja
Pdmax: Maximum Power Dissipation, Tjmax: Junction Temperature = 125°C
Ta: Ambient Temperature, θja: Thermal Resistance of package(SSOP20) = 333°C/W
Power dissipation of the NJU8755 itself is calculated, as shown below.
Pd(W) = PO(W) X RO(Ω) / RL(Ω) + PdIC(W)
Pd: Power Dissipation, PO: Output Power, RO: Internal Resistance(output driver)
RL: Load Resistance, PdIC: Power of internal circuit
-4-
Ver.2003-03-12
NJU8755
NJU3555
! ELECTRICAL CHARACTERISTICS
(Ta=25°C, VDD= VDDL= VDDR=5.0V, VSS=VSSL=VSSR=0V, Input Signal=1kHz,
Input Signal Level=200mVrms, Frequency Band=20Hz~20kHz,
Load Impedance=8Ω, 2nd-order 34kHz LC Filter(Q=0.85))
PARAMETER
SYMBOL
CONDITIONS
VDD
VDD,VDDP,VDDN Supply Voltage
ZIN
INL, INR pins
Input Impedance
AV
Voltage Gain
Eeff
Output Power Efficiency
Output THD=10%
THD
Po=0.6W
Output THD
Po
Output Power
Output THD=10%
S/N
SN
A weight
Dynamic Range
Drange
A weight
Channel Separation
Echn
EIAJ(1kHz)
Output Level Difference
CHD
Between L- and R- channels
Maximum Mute Attenuation
MAT
Operating Current (Standby)
IST
Operating Current
No Filter
IDD
(No signal input)
No Load
MUTE, STBY pins
VIH
Input Voltage
MUTE, STBY pins
VIL
MUTE, STBY pins
Input Leakage Current
ILK
MIN
2.7
80
60
TYP
5.0
20
23
0.05
1.2
80
83
-
MAX
5.25
0.08
-
UNIT
V
kΩ
dB
%
%
W/ch
dB
dB
dB
-
-
3
dB
90
-
-
1
dB
µA
-
7.5
10
mA
0.7VDD
0
-
-
VDD
0.3VDD
±1.0
V
V
µA
Note
5
5
5
Note 5) Test system of the output THD, S/N and Dynamic Range
The output THD, S/N and dynamic range are tested in the system shown in Figure1, where a 2nd-order
LC LPF and another filter incorporated in an audio analyzer are used.
Input Signal
NJU8755
2nd-order
LC LPF
NJU8755 Test Board
Filter
20kHz
(AES17)
THD
Measuring
Apparatus
Audio Analyzer
Figure 1. Output THD, S/N and Dynamic Range Test System
2nd-order LPF
Filters
Ver.2003-03-12
: fc=34kHz / Refer to “Typical Application Circuit”.
: 22Hz HPF + 20kHz LPF(AES17)
(with the A-Weight filter for S/N and Dynamic-range tests)
-5-
NJU8755
! TYPICAL APPLICATION CIRCUIT
•A918CY-220M is manufactured by TOKO, INC.
For detail information, please refer its technical papers.
A918CY-220M
VDD
10µF 0.1µF
22µH
OUTLP(6)
VDD(1)
1µF
VSS(20)
10µF
INR
2.2µF
INL(2)
COM(18)
INR(19)
NJU8755
INL
2.2µF
22µH
OUTLN(8)
VDDL(5,9,10)
8Ω Speaker
1µF
A918CY-220M
0.1µF
10µF
VDD
VSSL(7)
22µH
OUTRP(15)
A918CY-220M
MUTE(4)
STBY(17)
TEST(3)
22µH
OUTRN(13)
VDDR(11,12,16)
1µF
8Ω Speaker
1µF
A918CY-220M
0.1µF
10µF
VDD
VSSR(14)
Figure 2. Application Circuit example
Note 6) De-coupling capacitors must be connected between each power supply pin and GND.
The capacity value should be adjusted on the application circuit and the operation temperature. It may
malfunction if capacity value is small.
Note 7) The power supply for VDDL and VDDR require fast driving response performance such as a switching
regulator for better THD.
THD performance becomes worse by ripple if the capacity of De-coupling capacitor is small.
Note 8) The above circuit shows only application example and does not guarantee the any electrical
characteristics. Therefore, please test the circuit carefully to fit your application.
The cutoff frequency of the LC filter influences the quality of sound.
The Q factor of the LC filter must be less than “1”. Otherwise, the operating current increase when the
frequency of input signal is closed to the cutoff frequency.
Note 9) The transition time for MUTE and STBY signals must be less than 100µs. Otherwise, a malfunction may
be occurred.
Note 10) (1) – (20) indicates pin number.
[CAUTION]
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions. The
application circuits in this databook are
described only to show representative usages
of the product and not intended for the
guarantee or permission of any right including
the industrial rights.
-6-
Ver.2003-03-12
Similar pages