NJU8752
-1-
Analog Signal Input Class D Amplifier for Piezo Speaker
! GENERAL DESCRIPTION
NJU8752 is an analog signal input monaural class D
amplifier for Piezo speaker. The NJU8752 includes
Inversion operational amplifier input circuit, PWM
modulator, an 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.
The NJU8752 is configured as a BTL amplifier
capable of driving 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
achieves lower power operation for Piezo speaker, thus
the NJU8752 is suited for battery powered applications.
! FEATURES
# Piezo Speaker Driving
# 1-channel Analog 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)
6.0 ~ 13.75V (Output)
# C-MOS Technology
# Package Outline SSOP14
! BLOCK DIAGR AM
! PIN CONFIGURATION
! PACKAGE OUTLINE
NJU8752V
V
DD
IN
TEST 1
MUTE
V
SS
V
SS
COM
TEST 2
STBY
V
SS
1
2
3
4
5
14
13
12
11
10
6
7
9
8
OUT
P
V
DDO
OUT
N
V
DDO
Pulse
Width
Modulator
Short
Protector
V
DD
Control Logic Low Voltage
Detector
Soft Start
V
SS
+
-
+
-
IN
COM
MUTE TEST 1
STBY TEST 2
V
DDO
OUT
P
V
SS
V
DDO
OUT
N
V
SS
PRELIMINARY
NJU8752
- 2 -
! PIN DESCRIPTIO N
No. SYMBOL I/O Function
1 V
DD
− Power Supply: V
DD
=3.3V
2 IN I Signal Input
3 TEST 1 I
Maker test 1
This pin must be connected to GND.
4 MUTE I
Mute Control
Low : Mute ON High : Mute OFF
5 V
SS
− Positive Output Power GND : V
SS
=0V
6 OUT
P
O Positive Output
7 V
DDO
− Positive Output Power Supply : V
DDO
=13.75V max.
8 V
DDO
− Negative Output Power Supply : V
DDO
=13.75V max.
9 OUT
N
O Negative Output
10 V
SS
− Negative Output Power GND : V
SS
=0V
11 STBY I
Standby Control
Low : Standby ON High : Standby OFF
12 TEST 2 I
Maker test 2
This pin must be connected to GND.
13 COM − 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.
*Pin No. 4(MUTE) and 11(STBY) must be connected to V
DD
, when these pins are not used.
NJU3555NJU3555NJU8752
-3-
! FUNCTIONAL DESC RIPTION
(1) Signal Output
The OUT
P
and OUT
N
generate 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
DDO
, 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
NJU8752 enter a low-power state, and the output pins (OUT
P
and OUT
N
) are high impedance.
(3) Mute
By setting the MUTE pin to “L”, the Mute function is enabled. In the Mute mode, the 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 for prevention
to generate unwanted frequency, and the output pins (OUT
P
and OUT
N
) become in high impedance.
(5) Short Circuit Protection
The short protector, which protects the NJU8752 against 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
functions at 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.
NJU8752
- 4 -
! ABSOLUTE MAXIMUM R ATINGS
(Ta=25°C)
PARAMETER SYMBOL RATING UNIT
Supply Voltage V
DD
V
DDO
-0.3 ~ +4.0
-0.3 ~ +15.0
V
V
Input Voltage Vin -0.3 ~ V
DD
+0.3 V
Operating Temperature Topr -40 ~ +85 °C
Storage Temperature Tstg -40 ~ +125 °C
Power Dissipation SSOP14 P
D
300 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 CHAR ACTERISTICS
(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 Impedance=0.8µF, 2nd-order 34kHz LC Filter(Q=0.75))
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNIT Note
V
DD
Supply Voltage V
DD
3.0 3.3 3.6 V
V
DDO
Supply Voltage V
DDO
6.0 12.0 13.75 V
Input Impedance Z
IN
IN pin - 20 - kΩ
Voltage Gain A
V
- 31 - dB
Output THD THD Input Signal Level
=200mVrms - 0.05 0.08 % 4
Maximum Output Vo Output THD=10% 7 10 - Vrms
S/N SN A weight - 80 - dB 4
Dynamic Range Drange A weight - 83 - dB 4
Maximum Mute Attenuation MAT 90 - - dB
Operating Current(Stanby) I
ST
- - 1 µA
Operating Current
(No signal input) I
DD
No-load operating
No Signal Input - 3.5 10 mA
V
IH
MUTE, STBY pins 0.7V
DD
- V
DD
V
Input Voltage V
IL
MUTE, STBY pins 0 - 0.3V
DD
V
Input Leakage Current I
LK
MUTE, STBY pins - - ±1.0 µA
NJU3555NJU3555NJU8752
-5-
Note 4) 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 Figure 1, 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)
(with the A-Weight filter for S/N and Dynamic-range tests)
Input Signal
THD
Measuring
Apparatus
Filter
20kHz
(AES17)
2nd-order
LC LPF
NJU8752 Test Board Audio Analyzer
Figure 1. Output THD, S/N and Dynamic Range Test System
NJU8752
NJU8752
- 6 -
! TYPICAL APPLICATION CIRCUIT
Note 5) 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 6) The power supply for V
DDO
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 capacitors is small.
Note 7) 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 8) The transition time for MUTE and STBY signals must be less than 100us. Otherwise, a malfunction may
be occurred.
Note 9) (1)-(14) indicates pin number.
Figure 2. Application Circuit example
[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.
NJU8752
V
DD
(1)
V
SS
(14)
OUT
P
(6)
OUT
N
(9)
33~47uH
Piezo Speaker
0.1uF
0.1uF
V
DDO
(
7
)
V
SS
(5)
0.1uF 10uF
V
DDO
0.1uF
10uF
V
DD
IN(2) IN
COM(13)
MUTE(4)
STBY
(
11
)
0.1uF
10uF
V
DDO
(
8
)
V
SS
(10)
0.1uF 10uF
V
DDO
TEST1(3)
TEST2
(
12
)
33~47uH
5~10Ω
5~10Ω
0.5~2uF
3.3kΩ
0.01uF
•LLB2520 is manufactured by TOKO, INC.
For detail information, please refer its technical papers.
LLB2520
LLB2520
