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NJU8755
PRELIMINARY
Analog Signal Input Stereo Class D Power Amplifier
! 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.
! PACKAGE OUTLINE
NJU8755V
! FEATURES
# # # # # # # #
! PIN CONFIGURATION
1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 VSS INR COM STBY VDDR OUTRP VSSR OUTRN VDDR VDDR VDDL
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 VDDL ! BLOCK DIAGRAM VDD VSS
INL
+ +
Pulse Width Modulator
OUTLP VSSL VDDL OUTLN VSSL VDDR
Pulse Width Modulator
COM + + INR -
OUTRP VSSR VDDR OUTRN VSSR
Short Protector
Soft Start
Control
Logic
Low Voltage Detector
MUTE
STBY
TEST
Ver.2003-03-12
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NJU8755
! PIN DESCRIPTION
No. 1 2 3 4 5 9 10 6 7 8 11 12 16 13 14 15 SYMBOL VDD INL TEST MUTE VDDL OUTLP VSSL OUTLN VDDR OUTRN VSSR OUTRP I/O - I I I - O - O - O - O 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 L-channel Power Supply : VDDL=5.0V L-channel positive output L-channel Power GND L-channel negative output R-channel Power Supply : VDDR=5.0V
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.
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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
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NJU8755
! ABSOLUTE MAXIMUM RATINGS
(Ta=25C) 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)) /ja Pdmax: Maximum Power Dissipation, Tjmax: Junction Temperature = 125C Ta: Ambient Temperature, ja: Thermal Resistance of package(SSOP20) = 333C/W Power dissipation of the NJU8755 itself is calculated, as shown below. Pd(W) = PO(W) X RO() / RL() + PdIC(W) Pd: Power Dissipation, PO: Output Power, RO: Internal Resistance(output driver) RL: Load Resistance, PdIC: Power of internal circuit
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Ver.2003-03-12
NJU8755 NJU3555
! ELECTRICAL CHARACTERISTICS
(Ta=25C, VDD= VDDL= VDDR=5.0V, VSS=VSSL=VSSR=0V, Input Signal=1kHz, Input Signal Level=200mVrms, Frequency Band=20Hz~20kHz, Load Impedance=8, 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 90 0.7VDD 0 TYP 5.0 20 23 0.05 1.2 80 83 7.5 MAX 5.25 0.08 3 1 10 VDD 0.3VDD 1.0 UNIT V k dB % % W/ch dB dB dB dB dB A mA V V A 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
Filter 20kHz (AES17)
THD Measuring Apparatus
NJU8755 Test Board
Audio Analyzer
Figure 1. Output THD, S/N and Dynamic Range Test System
2nd-order LPF Filters
: fc=34kHz / Refer to "Typical Application Circuit". : 22Hz HPF + 20kHz LPF(AES17) (with the A-Weight filter for S/N and Dynamic-range tests)
Ver.2003-03-12
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NJU8755
! TYPICAL APPLICATION CIRCUIT
*A918CY-220M is manufactured by TOKO, INC. For detail information, please refer its technical papers.
A918CY-220M
VDD
10F 0.1F
22H
VDD(1) VSS(20)
OUTLP(6)
1F 22H
8 Speaker
1F
INL
INL(2) COM(18)
NJU8755
2.2F
OUTLN(8) VDDL(5,9,10) VSSL(7)
22H
A918CY-220M 0.1F 10F
10F 2.2F
VDD
INR
INR(19)
OUTRP(15)
A918CY-220M
1F
MUTE(4) STBY(17) TEST(3)
22H
8 Speaker
1F
OUTRN(13) VDDR(11,12,16) VSSR(14)
A918CY-220M 0.1F 10F
VDD
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 100s. 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.
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Ver.2003-03-12

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