NJU8752
PRELIMINARY
Analog Signal Input Class D Amplifier for Piezo Speaker
GENERAL DESCRIPTION
NJU8752
is a monaural analog signal input class D
amplifier for Piezo speaker. The
NJU8752
includes
Inversion operational amplifier input circuit, PWM
modulator, Output short protector and a low voltage
detector. Input part operates on 3.3V(TYP) as power
supply and Output part operates up to 13.75V(MAX).
Therefore, it drives Piezo speaker with Higher volume
and High efficiency.
By using equivalent capacitance of Piezo speaker,
the
NJU8752
is configured as a BTL amplifier capable
of operating Piezo speaker with the minimum external
components. A BTL configuration eliminates the need
for external AC coupling capacitors.
Class D achieves high output-efficiency, which leads
to low power operation for Piezo speaker, thus the
NJU8752
is ideally suited for battery powered
applications.
PACKAGE OUTLINE
NJU8752V
FEATURES
Piezo Speaker Driving
Analog Audio Signal Input, 1-channel BTL Output
Standby(Hi-Z), Mute Control
Built-in Low Voltage Detector
Built-in Short Protector
Operating Voltage
3.0 ~ 3.6V(Input)
9.0 ~ 13.75V(Output)
C-MOS Technology
Package Outline
SSOP14
PIN CONFIGURATION
V
DD
IN
TEST 1
MUTE
V
SS
OUT
P
V
DDO
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
SS
COM
TEST 2
STBY
V
SS
OUT
N
V
DDO
BLOCK DIAGRAM
V
DD
V
SS
V
DDO
IN
-
+
-
COM
+
Pulse
Width
Modulator
OUT
P
V
SS
V
DDO
OUT
N
V
SS
Short
Protector
Soft Start
Control
Logic
Low Voltage
Detector
MUTE
TEST 1
STBY
TEST 2
-1-
NJU8752
PIN DESCRIPTION
No.
1
2
Power Supply: V
DD
=3.3V
Signal Input
Maker test 1
3
TEST 1
I
This pin must be connected to GND.
Mute Control
4
MUTE
I
Low : Mute ON
High : Mute OFF
5
V
SS
−
Positive Power GND : V
SS
=0V
6
OUT
P
O
Positive Output
7
V
DDO
−
Positive Output Power Supply : V
DDO
=5.0V~13.75V
8
V
DDO
−
Negative Output Power Supply : V
DDO
=5.0V~13.75V
9
OUT
N
O
Negative Output
10
V
SS
−
Negative Power GND : V
SS
=0V
Standby Control
11
STBY
I
Low : Standby ON
High : Standby OFF
Maker test 2
12
TEST 2
I
This pin must be connected to GND.
13
COM
I
Analog common
14
V
SS
−
Power GND : V
SS
=0V
*Pin No. 5(V
SS
),10(V
SS
) and 14(V
SS
) must be used at the same voltage level
*Pin No. 7(V
DDO
) and 8(V
DDO
) must be used at the same voltage level.
SYMBOL
V
DD
IN
I/O
−
I
Function
INPUT PINS STRUCTURE(MUTE, STBY, TEST1, TEST2)
V
DD
Input Terminal
V
SS
Inside Circuit
-2-
NJU8752
NJU3555
FUNCTIONAL DESCRIPTION
(1) Output Signal
The OUT
P
and OUT
N
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 V
DDP
and V
DDN
, which are the power supply for output
drivers. To obtain better T.H.D. performance, the stabilization of the power is key.
(2) Standby
By setting the STBY pin to “L”, the standby mode is enabled. In the standby mode, the entire functions of the
NJU8752
enter a low-power state, and the output pins(OUT
P
and OUT
N
) are in high impedance.
(3) Mute
By setting the MUTE pin to “L”, the Mute function is enabled, and output pins(OUT
P
and OUT
N
) output square
wave(Duty: 50%).
(4) Low Voltage Detector
When the power supply voltage drops down to below V
DD
(MIN), the internal oscillation is halted not to
generate unwanted frequency, and the output pins(OUT
P
and OUT
N
) become in high impedance.
(5) Short Protection Circuit
The short protector, which protects the NJU8752 from high short-circuit current, turns off the output driver.
After about 5 seconds from the protection, the
NJU8752
returns to normal operation. The short protector is
enabled in response to the following accidents.
-Short between OUT
P
and OUT
N
-Short between OUT
P
and V
SS
-Short between OUT
N
and V
SS
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 the
NJU8752.
-3-
NJU8752
ABSOLUTE MAXIMUM RATINGS
(Ta=25°C)
PARAMETER
Supply Voltage
Input Voltage
Operating Temperature
Storage Temperature
Power Dissipation SSOP14
SYMBOL
V
DD
V
DDO
Vin
Topr
Tstg
P
D
RATING
-0.3 ~ +4.0
-0.3 ~ +15.0
-0.3 ~ V
DD
+0.3
-40 ~ +85
-40 ~ +125
300
UNIT
V
V
V
°C
°C
MW
Note 1) All voltage are relative to “V
SS
=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 V
DD
(Pin 1)-V
SS
(Pin 14), V
DDO
(Pin 7)-V
SS
(Pin 5) and V
DDO
(Pin 8)-V
SS
(Pin 10)
should be connected for stable operation.
ELECTRICAL CHARACTERISTICS
(Ta=25°C, V
DD
=3.3V, V
DDO
=12.0V, V
SS
=0V,
Input Signal=1kHz, Input Signal Level=200mVrms, Frequency Band=20Hz~20kHz,
Load Capacitance=0.8µF, 2nd-order 34kHz LC Filter (Q=0.75))
PARAMETER
V
DD
Supply Voltage
V
DDO
Supply Voltage
Output Power Efficiency
Output T.H.D.
Output Power
S/N
Dynamic Range
Maximum Mute Attenuation
Operating Current(Stanby)
Operating Current
(No signal input)
Input Voltage
Input Leakage Current
SYMBOL
CONDITIONS
MIN
3.0
9.0
80
-
-
T.B.D
T.B.D
-90
-
-
0.7V
DD
0
-
TYP
3.3
12.0
-
-
T.B.D
T.B.D
T.B.D
-
-
-
-
-
-
MAX
3.6
13.75
-
0.1
-
-
-
-
10
10
V
DD
0.3V
DD
±1.0
UNIT
V
V
%
%
W/ch
dB
dB
dB
µA
mA
V
V
µA
Note
Eeff
T.H.D.
Po
SN
Drange
MAT
I
ST
I
DD
V
IH
V
IL
I
LK
Output T.H.D.=10%
Po= T.B.D
Output T.H.D.=10%
A weight
A weight
4
No-load operating
No Signal Input
-4-
NJU8752
NJU3555
Note 4) Test system of the output T.H.D., S/N, Dynamic Range
The output T.H.D., S/N and dynamic range are tested in the system shown in Figure 1, where a
2nd-order LC LPF and another filter incorporated in an audio analyzer are used.
Input Signal
NJU8752
2nd-order
LC LPF
Filter
20kHz
(AES17)
THD
Measuring
Apparatus
NJU8752
Test Board
Audio Analyzer
Figure 1. Output T.H.D., 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)
-5-
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