NJU8757
-1-
Ve
r
.2008-08-27
ANALOG SIGNAL INPUT 2.5W STEREO Class-D POWER AMPLIFIER
GENERAL DESCRIPTION
The NJU8757 is an analog signal input stereo
class-D power amplifier. The NJU8757 incorporates
BTL amplifiers, which eliminate AC coupling capacitors,
and it is capable of driving up to 2.5W/channel into
RL=4ohms with simple external LC low-pass filters.
The NJU8757 includes PWM modulators, an output
short protector, a low voltage detector and a pop noise
reduction function.
Class-D operation achieves high power-efficiency,
which achieves longer battery life for battery powered
applications, thus the NJU8757 is suited for multimedia
speaker, PC, etc.
FEATURES
2-Channel Analog Differential Input
2-Channel BTL Outputs:2.5W/ch at 5V into 4 ohms
Standby(Hi-Z), Mute Control
Built-in Low Voltage Detector
Built-in Short Protector for each channel
Built-in Pop noise reduction
Operating Voltage:2.7 to 5.25V
CMOS Technology
Package Outline:SSOP32, QFN28-N2
BLOCK DIAGRAM
PIN CONFIGURATION
PACKAGE OUTLINE
NJU8757V
NJU8757KN2
OUTLP
VSSL
STBYb
VDDR
OUTRN
VSSR
OUTRP
VDDR
INLP
INRN
OUTLN
VDDL
INRP
MUTEb
VDD VSS
INLN
VDDL
1
2
3
4
5
6
7
8
9
10
11
13
14
15
16
12
17
32
31
30
29
28
27
26
25
24
23
22
20
19
18
21
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC NC
NC
COM
NC
INLN
MUTEb
VDDL
OUTLP
VSSL
VSSL
OUTLN
NC
VDDL
NC
NC
NC
VDDR
NC
INLP
NC
VDD
COM
VSS
NC
INRP
INRN
STBYb
VDDR
OUTRP
VSSR
VSSR
OUTRN
28
1
STBYb
MUTEb
Control Logic
VDDL
VSSL
VSSL
VDDL
OUTLN
OUTLP
VDD VSS
VDDR
VSSR
OUTRP
Pulse
Width
Modulator VDDR
VSSR
OUTRN
Low Voltage
Detector
Soft Start
Pulse
Width
Modulator
INLP
COM
INLN
INRN
INRP
Short
Protection
Short
Protection
Pre
A
mplifie
r
Pre
A
mplifie
r
NJU8757
- 2 - Ver.2008-08-27
PIN DESCRIPTION
No.
SSOP32 QFN28-N2 SYMBOL I/O FUNCTION
4 26 VDD - Power Supply : VDD=5.0V
5 28 INLP I L-channel Positive input
6 1 INLN I L-channel Negative input
7 2 MUTEb I
Mute control
Low : Mute ON High : Mute OFF
8,12 3,9 VDDL - L-channel Power Supply : VDDL=5.0V
9 4 OUTLP O L-channel positive output
10 5,6 VSSL - L-channel Power GND
11 7 OUTLN O L-channel negative output
21,25 13,19 VDDR - R-channel Power Supply : VDDR=5.0V
22 15 OUTRN O R-channel negative output
23 16,17 VSSR - R-channel Power GND : VSSR=0V
24 18 OUTRP O R-channel positive output
26 20 STBYb I
Standby control
Low : Standby ON High : Standby OFF
27 21 INRN I R-channel Negative input
28 22 INRP I L-channel Positive input
29 24 VSS - Power GND : VSS=0V
30 25 COM I Analog common
Note 1) The relations of ”VSS= VSSL= VSSR=0V” and “VDD= VDDL=VDDR” must be maintained.
Note 2) MUTEb and STBYb must be connected to VDD, when these pins are not used.
NJU3555NJU8757
-3-
Ver.2008-08-27
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+N performance, the stabilization of the power is required.
(2) Standby
By setting the STBYB pin to “L”, the standby mode is enabled. In the standby mode, the entire functions of the
NJU8757 enter a low-power state, and the output pins(OUTLP/LN and OUTRP/RN) are high impedance.
(3) Mute
By setting the MUTEB 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 Protection
The short protector, which protects the NJU8757 against high short-circuit current, turns off the output drivers
of L-channel and R-channel independently. About 8 seconds after the protection, the NJU8757 returns to
normal operation. When only single-channel shorted, the other channel operates normally unless shorted.
However If power supply voltage exceeds operating voltage range, both of short protectors may work together.
The short-protector operates at following accidents.
• Short between OUTLP and OUTLN
• Short between OUTLP and VSSL
• Short between OUTLN and VSSL
• Short between OUTRP and OUTRN
• Short between OUTRP and VSSR
• Short between OUTRN and VSSR
Note 3) The detectable current and the period for the protection depend on the power supply voltage and
ambient temperature.
Note 4) 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 the NJU8757.
NJU8757
- 4 - Ver.2008-08-27
ABSOLUTE MAXIMUM RATINGS
(Ta=25°C)
PARAMETER SYMBOL CONDITIONS RATING UNIT
OUTLP–VDDL,OUT LN–VDDL
OUTRP–VDDR,OUT RN–VDDR
With Schottky barrier diode
-0.3 to + 5.5
Supply Voltage
VDD
VDDL
VDDR OUTLP–VDDL,OUT LN–VDDL
OUTRP–VDDR,OUT RN–VDDR
Without Schottky barrier diode
-0.3 to + 5.0
V
Input Voltage Vin - -0.3 to VDD+0.3 V
Junction Temperature Tj - -40 to +125 °C
Ambient Temperature Ta - -40 to +85 °C
Storage Temperature Tstg - -40 to +125 °C
PDS2 2 layers(EIAJ) SSOP32 1.0
PDS4 4 layers(EIAJ) SSOP32 1.5
PDQ2 2 layers(EIAJ) QFN28-N2 0.75
Power Dissipation
PDQ4 4 layers(EIAJ) QFN28-N2 1.8
W
Note 5) All voltage are relative to “VSS= VSSL= VSSR=0V” reference.
Note 6) The LSI must be used inside of the “Absolute maximum ratings”. Otherwise, a stress may cause
permanent damage to the LSI.
Note 7) Refer to “Typical Application Circuit” for the Schottky barrier diode.
Note 8) Power Dissipation
The class-D amplifiers operate with high power efficiency and low dissipation power compared to
general analog-amplifiers. In theory, the NJU8757 actualize quite high output-power such as
2.5W/channel at 5V operation into 4 ohms load, and total power is supposed to be 5.0W. For this
reason, it looks as if the NJU8757 exceeds the absolute maximum rating of the power dissipation.
However, in practice, the effective output-power of usual music sound is only about 1/5 to 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.
θja = 100°C / W ,2 layers(EIAJ) SSOP32
θja = 66.7°C / W ,4 layers(EIAJ) SSOP32
θja = 133.3°C / W ,2 layers(EIAJ) QFN28-N2
θja = 55.6°C / W ,4 layers(EIAJ) QFN28-N2
Power dissipation of the NJU8757 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 internal circuit
NJU3555NJU8757
-5-
Ver.2008-08-27
ELECTRICAL CHARACTERISTICS
(Ta=25°C, VDD= VDDL= VDDR=5.0V, Input Signal=1kHz, Input Signal Level=200mVrms,
Frequency Band=20Hz~20kHz, Load Impedance=4Ω, LC Filter(L=10µH, C=1µF)
PARAMETER CONDITIONS SYMBOL MIN TYP MAX UNIT
OUTLP–VDDL,OUT LN–VDDL
OUTRP–VDDR,OUT RN–VDDR
With Schottky barrier diode
VDD1 2.7 5.0 5.25
VDD,VDDP,VDDN
Supply Voltage OUTLP–VDDL,OUT LN–VDDL
OUTRP–VDDR,OUT RN–VDDR
Without Schottky barrier diode
VDD2 2.7 - 4.5
V
VIH 0.7VDD - VDD V
Input Voltage MUTEb,STBYb VIL 0 - 0.3VDD V
Drain-Source
On-state
Resistance
(Low-side)
OUTLP=0.01V,OUTLN=0.01V
OUTRP=0.01V,OUTRN=0.01V RDSL - 0.4 - Ω
Drain-Source
On-state
Resistance
(High-side)
OUTLP=VDDL-0.01V,OUTLN=VDDL-0.01V
OUTRP=VDDR-0.01V,OUTRN=VDDR-0.01V RDSH - 0.4 - Ω
Operating Current
(Standby) - IST - 0.1 1 µA
Operating Current
(No signal input) No Filter, No Load IDD - 7.5 10 mA
Startup Time MUTEb=L TON - 180 360 ms
INRP,INLP R
INP - 35 -
Input Resistance INRN,INLN R
INN - 280 -
kΩ
MUTEb,STBYb=5V or 0V ILK - - ±1
INRP,INLP=5V or 0V ILKP - - ±50
Input Leakage
Current INRN,INLN=5V or 0V ILKN - - ±25
µA
Voltage Gain No Filter, No Load AV - 22.9 - dB
Note 9) Startup Time : It is a time until the output driver is worked from the STBYb ON.
NJU8757
- 6 - Ver.2008-08-27
(Ta=25°C, VDD= VDDL= VDDR=5.0V, Input Signal=1kHz, Input Signal Level=200mVrms,
Frequency Band=20Hz~20kHz, Load Impedance=8Ω, LC Filter(L=22µH, C=0.47µF)
PARAMETER CONDITIONS SYMBOL MIN TYP MAX UNIT
Output Power Efficiency THD+N=10% Eeff8 - 87 - %
THD+N Po=0.5W THD+N8 - 0.02 - %
Output Power THD+N=10% Po8 - 1.5 -
W/ch
S/N A-weight
SNR8 - 83 - dB
Channel Separation 1kHz Echn8 - 78 - dB
Maximum Mute Attenuation 1kHz MAT8 - 85 - dB
Noise floor A-weight VN8 - 200 - µVrms
(Ta=25°C, VDD= VDDL= VDDR=5.0V, Input Signal=1kHz, Input Signal Level=200mVrms,
Frequency Band=20Hz~20kHz, Load Impedance=4Ω, LC Filter(L=10µH, C=1µF)
PARAMETER CONDITIONS SYMBOL MIN TYP MAX UNIT
Output Power Efficiency THD+N =10% Eeff4 - 79 - %
THD+N Po=1W THD+N4 - 0.02 - %
Output Power THD+N=10% Po4 - 2.5 -
W/ch
S/N A-weight
SNR4 - 83 - dB
Channel Separation 1kHz Echn4 - 78 - dB
Maximum Mute Attenuation 1kHz MAT4 - 85 - dB
Noise floor A-weight VN4 - 200 - µVrms
Note 10) Test system of the output THD+N.
The output THD+N is tested in the system shown in Figure1, where a 2nd-order LC LPF and another
filter incorporated in an audio analyzer are used.
2nd-order LPF : Refer to “Typical Application Circuit”.
Filters : 22Hz HPF + 20kHz LPF(AES17)
Figure 1. Output THD+N
Input
Signal
NJU8757 THD+N
Meter
LPF
20kHz
(AES17)
2nd-orde
r
LC LPF
NJU8757 Test Board Audio Analyzer
HPF
22Hz
NJU3555NJU8757
-7-
Ver.2008-08-27
TYPICAL APPLICATION CIRCUIT
Figure2. Application Circuit example
LC filter
RL(Ω)L(µH) C(µF)
4 10 * 1
8 22 ** 0.47
Schottky barrier diode
Refer to 11DQ04(Nihon Inter)
NJU8757
VDD
VSS
OUTLP
OUTLN
0.1
µ
F
10
µ
F
INLP
INLP
INRN
COM
MUTEb
STBYb
2.2
µ
F
2.2
µ
F
10
µ
F
OUTRP
OUTRN
C
Speaker
RL
L C
L
INRP
INRP 2.2
µ
F
INRN
INLN
INLN 2.2
µ
F
+
+
C
Speaker
RL
L C
VDDL
VSSL
1
µ
F
10
µ
F
+
VDDR
VSSR
1
µ
F
10
µ
F
+
L
Coil of LC filter
RL=4Ω
Refer to LQH55DN100M03(muRata)
RL=8Ω
Refer to LQH55DN220M03(muRata)
NJU8757
- 8 - Ver.2008-08-27
Note 11) 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 12) The power supply for VDDL and VDDR require fast driving response performance such as a switching
regulator for better THD+N.
Note 13) THD+N performance becomes worse by ripple if the capacity of De-coupling capacitor is small.
Note 14) The transition time for MUTEb and STBYb signals must be less than 100µs. Otherwise, a malfunction
may be occurred.
Note 15) It is necessary to connect the schottky barrier diode and snubber circuit to OUTLP, OUTLN, OUTRP and
OUTRN terminal for terminal protection. (Recommended schottky barrier diode: Reverse Current is less
than 10mA under the condition of Ta=150°C,VDD=5V and Forward Voltage is about 0.55V under the
condition of Ta=25°C,IF =1A. Recommended Cs of snubber circuit: temperature compensating type,
Rs: rated wattage is more than 1/4W.
Note 16) Recommended Coil of LC filter: Rated current is more than 1700mA under the condition of RL=4Ωand
more than 800mA under the condition of RL=8Ω
Note 17) 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 18) 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.
[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.
Figure3. Application Circuit example
Snubber Circuit
NJU8757
VDD
VSS
OUTLP
OUTLN
0.1
µ
F
10
µ
F
INLP
INLP
INRN
COM
MUTEb
STBYb
2.2
µ
F
2.2
µ
F
10
µ
F
OUTRP
OUTRN
C
Speaker
RL
L C
L
INRP
INRP 2.2
µ
F
INRN
INLN
INLN 2.2
µ
F
+
+
C
Speaker
RL
L C
VDDL
VSSL
1
µ
F
10
µ
F
+
VDDR
VSSR
1
µ
F
10
µ
F
+
L
Recommended parts
C
RL=4Ω
Refer to LQH55DN100M03(muRata)
RL=8Ω
Refer to LQH55DN220M03(muRata)
Cs
RL=4Ω
Refer to RPE2C1H221J2K1A01B (muRata)
RL=8Ω
Refer to RPE2C1H151J2K1A01B (muRata)
RL[Ω]L[µH] C[µF] CS[pF] RS[Ω]
4 10 1 220 1.5
8 22 0.47 150 1.5
CC
RC
CC
RC
