MAX9788_V01 [MAXIM]
14VP-P,Class G Ceramic Speaker Driver;
| 型号： | MAX9788_V01 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 14VP-P,Class G Ceramic Speaker Driver |
| 文件： | 总13页 (文件大小：203K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0710; Rev 3; 5/08
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
General Description
Features
The MAX9788 features a mono Class G power amplifier
with an integrated inverting charge-pump power supply
specifically designed to drive the high capacitance of a
ceramic loudspeaker. The charge pump can supply
greater than 700mA of peak output current at 5.5VDC,
♦ Integrated Charge-Pump Power Supply—No
Inductor Required
♦ 14V
Voltage Swing into Piezoelectric Speaker
P-P
♦ 2.7V to 5.5V Single-Supply Operation
♦ Clickless/Popless Operation
guaranteeing an output of 14V
.
P-P
The MAX9788 maximizes battery life by offering high-
performance efficiency. Maxim’s proprietary Class G
output stage provides efficiency levels greater than
Class AB devices without the EMI penalties commonly
associated with Class D amplifiers.
♦ Small Thermally Efficient Packages
4mm x 4mm 28-Pin TQFN
2mm x 2.5mm 20-Bump WLP
The MAX9788 is ideally suited to deliver the high out-
put-voltage swing required to drive ceramic/piezoelec-
tric speakers.
Ordering Information
The device utilizes fully differential inputs and outputs,
comprehensive click-and-pop suppression, shutdown
control, and soft-start circuitry. The MAX9788 is fully spec-
ified over the -40°C to +85°C extended temperature range
and is available in small lead-free 28-pin TQFN (4mm x
4mm) or 20-bump WLP (2mm x 2.5mm) packages.
PART
PIN-PACKAGE
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
MAX9788EWP+TG45 20 WLP
MAX9788ETI+
28 TQFN-EP*
+Denotes a lead-free package.
T = Tape and reel.
G45 indicates protective die coating.
*EP = Exposed pad.
Applications
Cell Phones
Smartphones
MP3 Players
Personal Media Players
Handheld Gaming
Consoles
Typical Application Circuit/Functional Diagram and Pin
Configurations appear at end of data sheet.
Notebook Computers
Simplified Block Diagram
2.7V TO 5.5V
V
CC
CPV
DD
FB+
MAX9788
R
FB+
C
C
IN
R
IN+
IN+
IN-
OUT+
OUT-
CLASS G
OUTPUT
STAGE
+
-
R
IN-
IN
R
FB-
CHARGE
PUMP
FB-
GND
CPGND
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
14V ,Class G Ceramic Speaker Driver
P-P
ABSOLUTE MAXIMUM RATINGS
(Voltages with respect to GND.)
, CPV
CPV , CPGND, C1P, C1N, PV .................................800mA
DD SS
Any Other Pin ..................................................................20mA
V
CC
.............................................................-0.3V to +6V
DD
PV , SV ...............................................................-6V to +0.3V
CPGND..................................................................-0.3V to +0.3V
Continuous Power Dissipation (T = +70°C)
20-Bump WLP (derate 10.3mW/°C
SS
SS
A
OUT+, OUT-...................................(SV - 0.3V) to (V
IN+, IN-, FB+, FB- ......................................-0.3V to (V
+ 0.3V)
+ 0.3V)
above +70°C) (Note 1)..................................................827mW
28-Pin TQFN (derate 20.8mW/°C above +70°C) ........1667mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) ................................+300°C
Bump Temperature (soldering) Reflow............................+235°C
SS
CC
CC
C1N .........................................(PV - 0.3V) to (CPGND + 0.3V)
SS
C1P ......................................(CPGND - 0.3V) to (CPV
FS, SHDN ...................................................-0.3V to (V
Continuous Current Into/Out of
+ 0.3V)
+ 0.3V)
DD
CC
MAX978
OUT+, OUT-, V , GND, SV .....................................800mA
CC
SS
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, see www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
= V
= V
= 3.6V, V
= V
= 0V, R
= R = 10kΩ, R
= R
= 10kΩ, R = 100kΩ, C1 = 4.7µF, C2 =
CC
CPVDD
SHDN
GND
CPGND
IN+
IN-
FB+
FB- FS
10µF; load connected between OUT+ and OUT-, Z
= 10Ω + 1µF, unless otherwise stated; T = T
to T
, unless otherwise
LOAD
A
MIN
MAX
noted. Typical values are at T = +25°C.) (Notes 2, 3)
A
PARAMETER
GENERAL
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage Range
Quiescent Current
Shutdown Current
V
Inferred from PSRR test
2.7
5.5
12
5
V
CC
I
8
mA
µA
CC
I
SHDN = GND
0.3
SHDN
Time from shutdown or power-on to full
operation
Turn-On Time
t
50
1.24
83
ms
V
ON
Input DC Bias Voltage
V
IN_ inputs (Note 4)
1.1
55
1.4
BIAS
I
I
= 0mA (slow mode)
110
LOAD
LOAD
Charge-Pump Oscillator
Frequency
f
kHz
OSC
> 100mA (normal mode)
230
1.4
330
470
V
V
IH
IL
SHDN Input Threshold
(Note 5)
V
0.4
1
SHDN Input Leakage Current
µA
SPEAKER AMPLIFIER
T
T
= +25°C
3
15
20
A
Output Offset Voltage
V
V
mV
OS
≤ T ≤ T
MAX
MIN
A
Peak voltage into/out of shutdown
A-weighted, 32 samples per second
(Notes 6, 7)
Click-and-Pop Level
Voltage Gain
-67
dBV
dB
CP
A
(Notes 4, 8)
11.5
12
7.1
5.9
5.1
4.2
12.5
V
V
V
V
V
= 5V
CC
CC
CC
CC
= 4.2V
= 3.6V
= 3.0V
Output Voltage
V
f = 1kHz, 1% THD+N
V
RMS
OUT
2
_______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= V
= 3.6V, V
= V
= 0V, R
= R = 10kΩ, R
= R
= 10kΩ, R = 100kΩ, C1 = 4.7µF, C2 =
CC
CPVDD
SHDN
GND
CPGND
IN+
IN-
FB+
FB- FS
10µF; load connected between OUT+ and OUT-, Z
noted. Typical values are at T = +25°C.) (Notes 2, 3)
= 10Ω + 1µF, unless otherwise stated; T = T
to T
, unless otherwise
LOAD
A
MIN
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
6.5
MAX
UNITS
V
V
V
V
V
V
V
V
= 5V
CC
CC
CC
CC
CC
CC
CC
CC
= 4.2V
= 3.6V
= 3.0V
= 5V
5.4
f = 10kHz, 1% THD+N,
Z = 1µF + 10Ω, no load
Output Voltage
V
P
V
OUT
OUT
RMS
W
L
4.7
3.3
2.4
= 4.2V
= 3.6V
= 3.0V
1.67
1.25
0.8
1% THD+N, f = 1kHz,
Continuous Output Power
R = 8Ω
L
V
= 2.7V to 5.5V
63
77
CC
f = 217Hz, 200mV
ripple
77
P-P
Power-Supply Rejection Ratio
(Note 4)
PSRR
dB
%
f = 1kHz, 200mV
ripple
77
P-P
f = 20kHz, 200mV
ripple
58
P-P
Z = 1µF + 10Ω, V
L
= 1kHz / 1.9V
= 1kHz / 4.0V
0.002
0.08
OUT
OUT
RMS
Total Harmonic Distortion Plus
Noise
THD+N
Z = 1µF + 10Ω, V
L
RMS
Signal-to-Noise Ratio
SNR
V
= 5.1V
, A-weighted
108
dB
dB
OUT
RMS
Common-Mode Rejection Ratio
CMRR
f
= 1kHz (Note 9)
68
IN
V
V
= 5V
106
105
CC
CC
Dynamic Range
DR
A-weighted (Note 10)
dB
= 3.6V
Note 2:
Note 3:
All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Testing performed with resistive and capacitive loads to simulate an actual ceramic/piezoelectric speaker load,
Z = 1µF + 10Ω.
L
Note 4:
Input DC bias voltage determines the maximum voltage swing of the input signal. Inputing a signal with a peak voltage
of greater than the input DC bias voltage results in clipping.
Note 5:
Note 6:
Note 7:
1.8V logic compatible.
Amplifier/inputs AC-coupled to GND.
Testing performed at room temperature with 10Ω resistive load in series with 1µF capacitive load connected across the BTL
output for speaker amplifier. Mode transitions are controlled by SHDN. V is the peak output transient expressed in dBV.
CP
Note 8:
Note 9:
Voltage gain is defined as: [V
- V
] / [V
- V ].
IN+ IN-
OUT+
OUT-
PV is forced to -3.6V to simulate boosted rail.
SS
Note 10: Dynamic range is calculated by measuring the RMS voltage difference between a -60dBFS output signal and the noise
floor, then adding 60dB. Full scale is defined as the output signal needed to achieve 1% THD+N.
R
IN_
and R
have 0.5% tolerance. The Class G output stage has 12dB of gain. Any gain or attenuation at the input
FB_
stage will add to or subtract from the gain of the Class G output.
_______________________________________________________________________________________
3
14V ,Class G Ceramic Speaker Driver
P-P
Typical Operating Characteristics
(V
= V
L
= V
= 3.6V, V
= V
= 0V, R
= R = 10kΩ, R
= R
= 10kΩ, R = 100kΩ, C1 = 4.7µF, C2 =
CC
CPVDD
SHDN
GND
CPGND
IN+
IN-
FB+
FB- FS
10µF, Z = 1µF + 10Ω; load terminated between OUT+ and OUT-, unless otherwise stated; T = T
to T , unless otherwise noted.
MAX
A
MIN
Typical values are at T = +25°C.) (Notes 1, 2)
A
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
10
1
10
1
10
V
CC
= 3.6V
V
= 5V
CC
V
CC
= 2.7V
MAX978
1
0.1
V
= 4V
RMS
OUT
V
= 5.9V
RMS
V
= 3V
RMS
OUT
OUT
0.1
0.1
0.01
V
= 1.25V
100
OUT
RMS
0.01
0.001
V
= 1.9V
0.01
0.001
OUT RMS
V
= 3V
RMS
OUT
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
10
1k
FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
10
1
10
1
10
1
V
CC
= 3.6V
V
CC
= 5V
V
= 2.7V
CC
f = 10kHz
IN
f
IN
= 10kHz
f
IN
= 10kHz
f
= 1kHz
IN
f
= 1kHz
IN
f
= 1kHz
IN
0.1
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
f
= 20Hz
IN
f
IN
= 20Hz
4
f
= 20Hz
IN
5
6
7
8
0
1
2
3
4
5
0
1
3
5
6
0
1
2
3
4
2
OUTPUT VOLTAGE (V
OUTPUT VOLTAGE (V
)
OUTPUT VOLTAGE (V
)
RMS)
RMS
RMS
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
POWER CONSUMPTION
vs. OUTPUT VOLTAGE
POWER CONSUMPTION
vs. OUTPUT VOLTAGE
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
100
200
175
150
125
100
75
V
= 200mV
P-P
RIPPLE
75
50
25
0
50
V
= 2.7V
CC
V
= 3.6V
CC
f
= 1kHz
IN
25
f = 1kHz
IN
1% THD+N
3
4
1% THD+N
4
0
2
10
100
1k
FREQUENCY (Hz)
10k
100k
0
1
0
1
2
3
5
OUTPUT VOLTAGE (V
)
OUTPUT VOLTAGE (V
)
RMS
RMS
4
_______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
Typical Operating Characteristics (continued)
(V
= V
L
= V
= 3.6V, V
= V
= 0V, R
= R = 10kΩ, R
= R
= 10kΩ, R = 100kΩ, C1 = 4.7µF, C2 =
CC
CPVDD
SHDN
GND
CPGND
IN+
IN-
FB+
FB- FS
10µF, Z = 1µF + 10Ω; load terminated between OUT+ and OUT-, unless otherwise stated; T = T
to T , unless otherwise noted.
MAX
A
MIN
Typical values are at T = +25°C.) (Notes 1, 2)
A
POWER CONSUMPTION
vs. OUTPUT VOLTAGE
SHUTDOWN WAVEFORM
STARTUP WAVEFORM
MAX9788 toc12
MAX9788 toc11
350
300
250
200
150
100
SHDN
5V/div
SHDN
5V/div
OUT+ - OUT-
500mV/div
OUT+ - OUT-
500mV/div
V
= 5V
= 1kHz
CC
50
0
f
IN
1% THD+N
0
1
2
3
4
5
6
7
10ms/div
10ms/div
OUTPUT VOLTAGE (V
)
RMS
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
CLASS G OUTPUT WAVEFORM
MAX9788 toc13
12
10
8
OUT+
5V/div
OUT-
5V/div
6
4
OUT+ - OUT-
10V/div
2
0
1% THD+N
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
200μs/div
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. OUTPUT VOLTAGE
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
70
60
50
40
30
20
10
0
V
= 5V
= 1kHz
CC
f
IN
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
0
1
2
3
4
5
6
7
OUTPUT VOLTAGE (V
)
RMS
_______________________________________________________________________________________
5
14V ,Class G Ceramic Speaker Driver
P-P
Typical Operating Characteristics (continued)
(V
= V
L
= V
= 3.6V, V
= V
= 0V, R
= R = 10kΩ, R
= R
= 10kΩ, R = 100kΩ, C1 = 4.7µF, C2 =
CC
CPVDD
SHDN
GND
CPGND
IN+
IN-
FB+
FB- FS
10µF, Z = 1µF + 10Ω; load terminated between OUT+ and OUT-, unless otherwise stated; T = T
to T , unless otherwise noted.
MAX
A
MIN
Typical values are at T = +25°C.) (Notes 1, 2)
A
OUTPUT AMPLITUDE
vs. FREQUENCY
WLP PACKAGE THERMAL DISSIPATION
FREQUENCY RESPONSE
AND OUTPUT POWER vs. TEMPERATURE
MAX9788 toc19
8
20
18
16
14
12
10
8
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 2V
RMS
V
CC
= 5V
V
= 5V
CC
OUT
7
6
5
4
3
2
1
0
MAX978
V
= 3.6V
CC
OUTPUT POWER
PACKAGE THERMAL
DISSIPATION
V
= 2.7V
CC
6
4
2
0
10
100
1k
10k
100k
10
100
1k
10k
100k
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
FREQUENCY (Hz)
FREQUENCY (Hz)
TEMPERATURE (°C)
Pin Description
PIN
NAME
SHDN
N.C.
FUNCTION
TQFN
WLP
1
B2
Shutdown
2, 5, 6, 8, 11, 17,
19, 23, 25, 28
—
No Connection. No internal connection.
Charge-Pump Flying Capacitor, Positive Terminal. Connect a 4.7µF
capacitor between C1P and C1N.
3
A2
C1P
4
7
A3
A4
A5
B5
B4
CPV
Charge-Pump Positive Supply
Negative Amplifier Feedback
Negative Amplifier Input
DD
FB-
9
IN-
IN+
FB+
10
12
Positive Amplifier Input
Positive Amplifier Feedback
Charge-Pump Frequency Set. Connect a 100kΩ resistor from FS to
GND to set the charge-pump switching frequency.
13
C5
FS
14, 22
15, 21
16
D1, D5
C2, C4
D4
V
Supply Voltage. Bypass with a 10µF capacitor to GND.
CC
SV
Amplifier Negative Power Supply. Connect to PV
Negative Amplifier Output
Ground
.
SS
SS
OUT-
GND
18
D3
20
D2
OUT+
Positive Amplifier Output
Charge-Pump Output. Connect a 10µF capacitor between PV and
SS
CPGND.
24
26
C1
B1
PV
SS
Charge-Pump Flying Capacitor, Negative Terminal. Connect a 4.7µF
capacitor between C1N and C1P.
C1N
27
EP
A1
—
CPGND
EP
Charge-Pump Ground. Connect to GND.
Exposed Pad. Connect the TQFN EP to GND.
6
_______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
As the output signal increases so a wider supply is need-
Detailed Description
ed, the device begins its transition to the higher supply
The MAX9788 Class G power amplifier with inverting
charge pump is the latest in linear amplifier technology.
The Class G output stage offers improved performance
over a Class AB amplifier while increasing efficiency to
extend battery life. The integrated inverting charge
pump generates a negative supply capable of deliver-
ing greater than 700mA.
range (V
to SV ) for the large signals. To ensure a
SS
CC
seamless transition between the low and high supply
ranges, both of the lower transistors are on so that:
I
= I + I
N1 N2
LOAD
As the output signal continues to increase, the transi-
tion to the high supply is complete. The device then
operates in the higher supply range, where the opera-
tion of the device is identical to a traditional dual-sup-
ply Class AB amplifier where:
The Class G output stage and the inverting charge
pump allow the MAX9788 to deliver a 14V
voltage
P-P
swing, up to two times greater than a traditional single-
supply linear amplifier.
I
= I
N2
LOAD
During operation, the output common-mode voltage of
the MAX9788 adjusts dynamically as the device transi-
tions between supply ranges.
Class G Operation
The MAX9788 Class G amplifier is a linear amplifier that
operates within a low (V
to GND) and high (V
to
CC
CC
SV ) supply range. Figure 1 illustrates the transition
Utilizing a Class G output stage with an inverting
SS
from the low to high supply range. For small signals,
charge pump allows the MAX9788 to realize a 20V
output swing with a 5V supply.
P-P
the device operates within the lower (V
to GND) sup-
CC
ply range. In this range, the operation of the device
is identical to a traditional single-supply Class AB
amplifier where:
I
= I
LOAD
N1
BTL CLASS G SUPPLY TRANSITION
V
CC
V
CC
V
CC
I
P
I
P
I
P
ON
P
ON
P
ON
P
Z
L
Z
L
Z
L
I
I
I
N1
N1
N1
N2
N1
N2
N1
N2
ON
ON
ON
OFF
I
N2
N2
OFF
ON
SV
SS
SV
SS
SV
SS
LOW SUPPLY RANGE OPERATION
I = I
SUPPLY TRANSITION
I = I + I
HIGH SUPPLY RANGE OPERATION
I = I
P
N1
P
N1 N2
P
N2
Figure 1. Class G Supply Transition
_______________________________________________________________________________________
7
14V ,Class G Ceramic Speaker Driver
P-P
where A is the desired voltage gain in dB. R
should
Inverting Charge Pump
The MAX9788 features an integrated charge pump with an
inverted supply rail that can supply greater than 700mA
over the positive 2.7V to 5.5V supply range. In the case of
the MAX9788, the charge pump generates the negative
V
IN+
be equal to R , and R
should be equal to R
.
FB-
IN-
FB+
The Class G output stage has a fixed gain of 4V/V
(12dB). Any gain or attenuation set by the external
input stage resistors will add to or subtract from this
fixed gain. See Figure 2.
supply rail (PV ) needed to create the higher supply
SS
range, which allows the output of the device to operate
over a greater dynamic range as the battery supply col-
lapses over time.
In differential input configurations, the common-mode
rejection ratio (CMRR) is primarily limited by the exter-
nal resistor and capacitor matching. Ideally, to achieve
the highest possible CMRR, the following external com-
ponents should be selected where:
MAX978
Shutdown Mode
The MAX9788 has a shutdown mode that reduces
power consumption and extends battery life. Driving
SHDN low places the MAX9788 in a low-power (0.3µA)
R
R
R
FB−
FB+
=
shutdown mode. Connect SHDN to V
operation.
for normal
CC
R
IN+
IN−
and
Click-and-Pop Suppression
The MAX9788 Class G amplifier features Maxim’s com-
prehensive, industry-leading click-and-pop suppres-
sion. During startup, the click-and-pop suppression
circuitry eliminates any audible transient sources inter-
nal to the device.
C
= C
IN+
IN−
Applications Information
MAX9788
FB+
Differential Input Amplifier
The MAX9788 features a differential input configuration,
making the device compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as PCs, noisy digital
signals can be picked up by the amplifier’s input
traces. The signals appear at the amplifier’s inputs as
common-mode noise. A differential input amplifier
amplifies the difference of the two inputs and signals
common to both inputs are canceled out. When config-
ured for differential inputs, the voltage gain of the
MAX9788 is set by:
R
FB+
C
IN+
R
IN+
IN+
IN-
+
-
CLASS G
OUTPUT
STAGE
R
IN-
C
IN-
R
FB-
FB-
⎡
⎤
⎥
⎛
⎞
R
FB_
⎢
A
= 20log 4 ×
dB
(
)
V
⎜
⎟
R
⎢
⎣
⎥
⎦
⎝
⎠
IN_
Figure 2. Gain Setting
8
_______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
Driving a Ceramic Speaker
Applications that require thin cases, such as today’s
mobile phones, demand that external components
have a small form factor. Dynamic loudspeakers that
use a cone and voice coil typically cannot conform to
the height requirements. The option for these applica-
tions is to use a ceramic/piezoelectric loudspeaker.
Component Selection
Input-Coupling Capacitor
The AC-coupling capacitors (C ) and input resistors
IN_
(R ) form highpass filters that remove any DC bias
IN_
from an input signal (see the Functional Diagram/
Typical Operating Circuit). C
blocks DC voltages
IN_
from the amplifier input. The -3dB point of the highpass
filter, assuming zero source impedance due to the
input signal source, is given by:
Ceramic speakers are much more capacitive than a con-
ventional loudspeaker. Typical capacitance values for
such a speaker can be greater than 1µF. High peak-to-
peak voltage drive is required to achieve acceptable
sound pressure levels. The high output voltage require-
ment coupled with the capacitive nature of the speaker
demand that the amplifier supply much more current at
high frequencies than at lower frequencies. Above 10kHz,
the typical speaker impedance can be less than 16Ω.
The MAX9788 is ideal for driving a capacitive ceramic
speaker. The high charge-pump current limit allows for a
flat frequency response out to 20kHz while maintaining
high output voltage swings. See the Frequency Response
graph in the Typical Operating Characteristics. Figure 3
shows a typical circuit for driving a ceramic speaker.
1
f−3dB
=
Hz
(
)
2π ×R
× C
IN_
IN_
Ceramic speakers generally perform best at frequen-
cies greater than 1kHz. Low frequencies can deflect
the piezoelectric speaker element so that high frequen-
cies cannot be properly reproduced. This can cause
distortion in the speaker’s usable frequency band.
Select a C so the f
closely matches the low fre-
IN
-3dB
quency response of the ceramic speaker. Use capaci-
tors with low-voltage coefficient dielectrics. Aluminum
electrolytic, tantalum, or film dielectric capacitors are
good choices for AC-coupling capacitors. Capacitors
with high-voltage coefficients, such as ceramics (non-
C0G dielectrics), can result in increased distortion at
low frequencies.
A 10Ω series resistance is recommended between the
amplifier output and the ceramic speaker load to ensure
the output of the amplifier sees some fixed resistance at
high frequencies when the speaker is essentially an
electrical short.
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 50mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric.
MAX9788
Flying Capacitor (C1)
The value of the flying capacitor (C1) affects the load
regulation and output resistance of the charge pump. A
C1 value that is too small degrades the device’s ability
to provide sufficient current drive. Increasing the value
of C1 improves load regulation and reduces the charge-
pump output resistance to an extent. Above 1µF, the on-
resistance of the switches and the ESR of C1 and C2
dominate. A 4.7µF capacitor is recommended.
R
L
OUT+
OUT-
CLASS G
OUTPUT
STAGE
Figure 3. Driving a Ceramic Speaker
_______________________________________________________________________________________
9
14V ,Class G Ceramic Speaker Driver
P-P
Hold Capacitor (C2)
Series Load Resistor
The capacitive nature of the ceramic speaker results in
very low impedances at high frequencies. To prevent
the ceramic speaker from shorting the MAX9788 output
at high frequencies, a series load resistor must be
used. The output load resistor and the ceramic speaker
create a lowpass filter. To set the rolloff frequency of
the output filter, the approximate capacitance of the
speaker must be known. This information can be
obtained from bench testing or from the ceramic
speaker manufacturer. A series load resistor greater
than 10Ω is recommended. Set the lowpass filter cutoff
frequency with the following equation:
The output capacitor value and ESR directly affect the
ripple at PV . Increasing C2 reduces output ripple.
SS
Likewise, decreasing the ESR of C2 reduces both rip-
ple and output resistance. A 10µF capacitor is recom-
mended.
Charge-Pump Frequency Set Resistor (R
)
FS
The charge pump operates in two modes. When the
charge pump is loaded below 100mA, it operates in a
slow mode where the oscillation frequency is reduced to
1/4 of its normal operating frequency. Once loaded, the
charge-pump oscillation frequency returns to normal
operation. In applications where the design may be sen-
sitive to the operating charge-pump oscillation frequen-
MAX978
1
cy, the value of the external resistor R can be changed
FS
f
=
Hz
(
)
LP
2π ×R × C
to adjust the charge-pump oscillation frequency shown
L
SPEAKER
in Figure 4. A 100kΩ resistor is recommended.
Ceramic Speaker Impedance
Characteristics
WLP Applications Information
For the latest application details on WLP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow tempera-
ture profile, as well as the latest information on reliability
testing results, go to the Maxim website at www.maxim-
ic.com/ucsp for the application note, UCSP—A Wafer-
Level Chip-Scale Package.
A 1µF capacitor is a good model for the ceramic
speaker as it best approximates the impedance of a
ceramic speaker over the audio band. When selecting
a capacitor to simulate a ceramic speaker, the voltage
rating or the capacitor must be equal to or higher than
the expected output voltage swing. See Figure 5.
CHARGE-PUMP OSCILLATION
IMPEDANCE vs. FREQUENCY
FREQUENCY vs. R
FS
1M
600
550
500
450
400
350
300
250
200
I
> 100mA
LOAD
1μF CAPACITOR
100k
10k
1k
CERAMIC
SPEAKER
100
10
0.001
0.01
0.1
1
10
100
50
75
100
(kΩ)
125
150
FREQUENCY (Hz)
R
FS
Figure 4. Charge-Pump Oscillation Frequency vs. R
Figure 5. Ceramic Speaker and Capacitor Impedance
FS
10 ______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
Typical Application Circuit/Functional Diagram
V
DD
SHDN
CONTROL
SIGNAL
0.1μF
*
20kΩ
14, 22
(D1, D5)
1 (B2)
SHDN
4 (A3)
V
CPV
DD
CC
12 (B4) FB+
MAX9788
R
FB+
C
R
L
10Ω
IN
R
IN+
10kΩ
0.47μF
10kΩ
OUT+ 20 (D2)
10 (B5) IN+
9 (A5) IN-
+
-
CLASS G
OUTPUT
STAGE
OUT- 16 (D4)
FS 13 (C5)
R
IN-
C
IN
R
FB-
10kΩ
0.47μF
10kΩ
CHARGE
PUMP
7 (A4) FB-
R
FS
100kΩ
GND CPGND
18 (D3) 27 (A1)
C1P PV
SV
C1N
26 (B1)
SS
SS
3 (A2)
15, 21
24 (C1)
(C2, C4)
C2
10μF
( ) WLP PACKAGE
C1
4.7μF
DEVICE SHOWN WITH A = 12dB
V
*SYSTEM-LEVEL REQUIREMENT TYPICALLY 10μF
______________________________________________________________________________________ 11
14V ,Class G Ceramic Speaker Driver
P-P
Pin Configurations
TOP VIEW
(BUMP SIDE DOWN)
TOP VIEW
MAX9788
4
1
2
3
5
+
MAX978
SHDN
N.C.
SV
SS
1
21
20
19
18
17
16
A
CPGND
CPV
DD
FB-
C1P
IN-
2
3
4
5
6
7
OUT+
N.C.
C1P
B
C1N
FB+
SV
SHDN
IN+
FS
CPV
DD
GND
N.C.
MAX9788
N.C.
N.C.
FB-
C
PV
SS
SV
SS
SS
OUT-
EP*
15 SV
SS
D
V
CC
GND
OUT-
OUT+
V
CC
WLP
THIN QFN
*EXPOSED PAD.
Package Information
Chip Information
For the latest package outline information and land patterns, go
PROCESS: BiCMOS
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
20 WLP
W202A2+1
T2844-1
21-0059
21-0139
28 TQFN
12 ______________________________________________________________________________________
14V ,Class G Ceramic Speaker Driver
P-P
MAX978
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
12/06
Initial release
—
Include tape and reel note, edit Absolute Maximum Ratings, update TQFN
package outline
11/07
1, 2,13, 14
Replaced USCP with WLP package throughout data sheet including new
WLP package outline, added new TOC 19 and Note 1
1, 2, 3, 6, 10, 11, 12,
15, 16
2
3
2/08
5/08
Updated Typical Application Circuit and corrected stylistic errors
1–6, 11
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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