MAX9728 [MAXIM]
60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown;
| 型号： | MAX9728 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 60mW, DirectDrive, Stereo Headphone Amplifiers with Shutdown |
| 文件： | 总19页 (文件大小：309K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3963; Rev 1; 7/09
60mW, DirectDrive, Stereo
Headphone Amplifiers with Shutdown
/MAX9728B
General Description
Features
♦ No Bulky DC-Blocking Capacitors Required
The MAX9728A/MAX9728B stereo headphone ampli-
fiers are designed for display and notebook applica-
tions or portable equipment where board space is at a
premium. These devices use a unique DirectDrive®
architecture to produce a ground-referenced output
from a single supply, eliminating the need for large DC-
blocking capacitors, saving cost, board space, and
component height. The MAX9728A offers an externally
adjustable gain, while the MAX9728B has an internally
preset gain of -1.5V/V. The MAX9728A/MAX9728B
deliver up to 60mW per channel into a 32Ω load and
have low 0.02% THD+N. An 80dB at 1kHz power-sup-
ply rejection ratio (PSRR) allows these devices to oper-
ate from noisy digital supplies without an additional
linear regulator. Comprehensive click-and-pop circuitry
suppresses audible clicks and pops on startup and
shutdown.
♦ Low-Power Shutdown Mode, < 0.1µA
♦ Adjustable Gain (MAX9728A) or Fixed -1.5V/V
Gain (MAX9728B)
♦ Low 0.02% THD+N
♦ High PSRR (80dB at 1kHz) Eliminates LDO
♦ Integrated Click-and-Pop Suppression
♦ 4.5V to 5.5V Single-Supply Operation
♦ Low Quiescent Current (3.5mA)
♦ Available in Space-Saving Packages
12-Pin Thin QFN (3mm x 3mm x 0.8mm)
14-Pin TSSOP (5mm x 4.4mm x 1.1mm)
The MAX9728A/MAX9728B operate from a single 4.5V
to 5.5V supply, consume only 3.5mA of supply current,
feature short-circuit and thermal-overload protection,
and are specified over the extended -40°C to +85°C
temperature range. The devices are available in tiny 12-
pin Thin QFN (3mm x 3mm x 0.8mm) and 14-pin
TSSOP packages (5mm x 4.4mm x 1.1mm).
Ordering Information
PART
GAIN (V/V) PIN-PACKAGE TOP MARK
MAX9728AETC+
MAX9728AEUD+
MAX9728BETC+
MAX9728BEUD+
Adj.
Adj.
-1.5
-1.5
12 TQFN-EP*
14 TSSOP
ABC
—
12 TQFN-EP*
14 TSSOP
ABD
—
Applications
CRT TVs
Note: All devices specified over the -40°C to +85°C operating
Notebook PCs
DVD Players
range.
+Denotes lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Multimedia Monitors
LCD/PDP Displays
DirectDrive is a registered trademark of Maxim Integrated
Product, Inc.
Pin Configurations appear at end of data sheet.
Block Diagrams
MAX9728B
MAX9728A
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
LEFT
AUDIO
INPUT
LEFT
AUDIO
CAPACITORS
INPUT
SHDN
SHDN
RIGHT
RIGHT
AUDIO
INPUT
FIXED GAIN ELIMINATES
AUDIO
EXTERNAL RESISTOR
INPUT
NETWORK
________________________________________________________________ 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.
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
ABSOLUTE MAXIMUM RATINGS
V
DD
to PGND............................................................-0.3V to +6V
OUT_ Short Circuit to SGND ......................................Continuous
Short Circuit between OUTL and OUTR ....................Continuous
PV to SV .........................................................-0.3V to +0.3V
SS
SS
PGND to SGND .....................................................-0.3V to +0.3V
C1P to PGND..............................................-0.3V to (V + 0.3V)
Continuous Input Current into PV ..................................260mA
Continuous Input Current (any other pin)......................... 20mA
SS
DD
C1N to PGND............................................(PV - 0.3V) to +0.3V
Continuous Power Dissipation (T = +70°C)
SS
A
PV and SV to PGND..........................................-6V to +0.3V
12-Pin TQFN (derate 14.7mW/°C above +70°C) .........1177mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) ...........727mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
SS
SS
IN_ to SGND (MAX9728A)..........................-0.3V to (V
+ 0.3V)
+ 0.3V)
DD
DD
IN_ to SGND (MAX9728B).............(SV - 0.3V) to (V
SS
OUT_ to SV (Note 1) ....-0.3V to Min (V
- SV + 0.3V, +9V)
SS
DD
SS
OUT_ to V
(Note 2) ......+0.3V to Max (SV - V
- 0.3V, -9V)
DD
DD
SS
SHDN to _GND.........................................................-0.3V to +6V
Note 1: OUTR and OUTL should be limited to no more than 9V above SV , or above V
+ 0.3V, whichever limits first.
SS
DD
DD
SS
Note 2: OUTR and OUTL should be limited to no more than 9V below V , or below SV - 0.3V, whichever limits first.
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
DD
= 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, R = ∞, resistive load reference to ground; for MAX9728A gain = -1.5V/V
L
/MAX9728B
(R = 20kΩ, R = 30kΩ); for MAX9728B gain = -1.5V/V (internally set), T = -40°C to +85°C, unless otherwise noted. Typical values
IN
F
A
are at T = +25°C, unless otherwise noted.) (Note 3)
A
PARAMETER
GENERAL
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage Range
Quiescent Current
V
4.5
5.5
5.5
1
V
DD
I
3.5
< 0.1
180
19
mA
µA
µs
CC
Shutdown Current
I
SHDN = SGND = PGND
MAX9728B, measured at IN_
SHDN
Shutdown to Full Operation
Input Impedance
t
SON
R
15
25
10
kΩ
mV
IN
Output Offset Voltage
V
1.5
86
OS
V
= 4.5V to 5.5V
DD
Power-Supply Rejection Ratio
PSRR
dB
f = 1kHz, 100mV
80
P-P
f = 20kHz, 100mV
65
P-P
R = 32Ω, THD+N = 1%
30
63
L
Output Power
Voltage Gain
P
mW
V/V
%
OUT
R = 16Ω, THD+N = 1%
L
42
A
MAX9728B (Note 4)
-1.52
-1.5
-1.48
V
Channel-to-Channel Gain
Tracking
MAX9728B
0.15
R = 1kΩ, V
= 2V , f = 1kHz
RMS IN
0.003
0.02
0.04
L
OUT
OUT
OUT
Total Harmonic Distortion Plus
Noise
THD+N
R = 32Ω, P
L
= 50mW, f = 1kHz
%
IN
R = 16Ω, P
L
= 35mW, f = 1kHz
IN
2
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
/MAX9728B
ELECTRICAL CHARACTERISTICS (continued)
(V
= 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, R = ∞, resistive load reference to ground; for MAX9728A gain = -1.5V/V
L
DD
IN
(R = 20kΩ, R = 30kΩ); for MAX9728B gain = -1.5V/V (internally set), T = -40°C to +85°C, unless otherwise noted. Typical values
are at T = +25°C, unless otherwise noted.) (Note 3)
F
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
102
105
98
MAX
UNITS
BW = 22Hz to 22kHz
R = 1kΩ,
L
V
= 2V
OUT
RMS
A-weighted
Signal-to-Noise Ratio
SNR
dB
BW = 22Hz to 22kHz
A-weighted
R = 32Ω,
L
P
= 50mW
OUT
101
0.5
Slew Rate
SR
V/µs
pF
Capacitive Drive
C
No sustained oscillations
100
L
L to R, R to L, f = 10kHz, R = 16Ω, P
15mW
=
L
OUT
Crosstalk
-70
dB
Charge-Pump Oscillator
Frequency
f
190
270
-67
-64
400
kHz
OSC
Into shutdown
R = 32Ω, peak voltage,
A-weighted, 32 samples per
second (Note 5)
L
Click-and-Pop Level
K
dB
CP
Out of
shutdown
DIGITAL INPUTS (SHDN)
Input Voltage High
V
2
V
V
INH
Input Voltage Low
V
0.8
1
INL
Input Leakage Current
µA
Note 3: All specifications are 100% tested at T = +25°C; temperature limits are guaranteed by design.
A
Note 4: Gain for the MAX9728A is adjustable.
Note 5: Test performed with a 32Ω resistive load connected to SGND. Mode transitions are controlled by SHDN. K level is calcu-
CP
lated as 20log[(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power
level)]. Units are expressed in dB.
_______________________________________________________________________________________
3
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Typical Operating Characteristics
(V
DD
= 5V, PGND = SGND = 0V, SHDN = V , C1 = C2 = 1µF, R = ∞, gain = -1.5V/V (R = 20kΩ, R = 30kΩ for the MAX9728A),
DD L IN F
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T = +25°C, unless otherwise noted.)
A
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
1
0.1
100
10
1
100
10
1
V
DD
= 5V
V
= 5V
V
DD
= 5V
DD
R = 16Ω
L
R = 16Ω
L
R = 32Ω
L
P
OUT
= 20mW
f
IN
= 1kHz
f
IN
= 1kHz
0.1
0.1
P
= 37mW
OUT
0.01
0.001
f
= 10kHz
IN
0.01
0.01
f
= 10kHz
100
IN
f
IN
= 20Hz
f
= 20Hz
IN
0.001
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0
20
40
60
80
100
0
20
40
60
80
120
OUTPUT POWER (mW)
OUTPUT POWER (mW)
/MAX9728B
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
OUTPUT POWER vs. SUPPLY VOLTAGE
OUTPUT POWER vs. SUPPLY VOLTAGE
70
60
50
40
30
20
10
0
1
0.1
120
100
80
60
40
20
0
V
= 5V
DD
THD+N = 10%
R = 32Ω
L
THD+N = 10%
P
OUT
= 30mW
THD+N = 1%
0.01
0.001
THD+N = 1%
P
= 50mW
OUT
f
= 1kHz
IN
f
= 1kHz
IN
R = 16Ω
L
R = 32Ω
L
4.5
5.0
5.5
10
100
1k
FREQUENCY (Hz)
10k
100k
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
/MAX9728B
Typical Operating Characteristics (continued)
(V
DD
= 5V, PGND = SGND = 0V, SHDN = V , C1 = C2 = 1µF, R = ∞, gain = -1.5V/V (R = 20kΩ, R = 30kΩ for the MAX9728A),
DD L IN F
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T = +25°C, unless otherwise noted.)
A
OUTPUT POWER
vs. LOAD RESISTANCE
POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
CROSSTALK vs. FREQUENCY
100
90
80
70
60
50
40
30
20
10
0
0
-20
0
-20
R = 32Ω
L
P
= 15mW
R = 16Ω
OUT
L
V
= 5V
DD
THD+N = 10%
-40
-40
-60
-60
LEFT TO RIGHT
-80
-80
THD+N = 1%
RIGHT TO LEFT
-100
-120
-100
-120
V
= 5V
= 1kHz
DD
f
IN
10
100
1000
10
100
1k
10k
100k
10
100
1k
10k
100k
LOAD RESISTANCE (Ω)
FREQUENCY (Hz)
FREQUENCY (Hz)
OUTPUT POWER vs. LOAD RESISTANCE
AND CHARGE-PUMP CAPACITOR SIZE
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
80
3.50
10
C1 = C2 = 2.2μF
C1 = C2 = 1μF
9
8
7
6
5
4
3
2
1
0
3.45
3.40
3.35
3.30
70
60
50
40
30
20
C1 = C2 = 0.47μF
V
DD
= 5V
3.25
3.20
f
= 1kHz
IN
NO LOAD INPUTS GROUND
NO LOAD INPUTS GROUND
THD+N = 1%
50
250
0
100
150
200
300
4.5
5.0
5.5
4.5
5.0
5.5
LOAD RESISTANCE (Ω)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Typical Operating Characteristics (continued)
(V
DD
= 5V, PGND = SGND = 0V, SHDN = V , C1 = C2 = 1µF, R = ∞, gain = -1.5V/V (R = 20kΩ, R = 30kΩ for the MAX9728A),
DD L IN F
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T = +25°C, unless otherwise noted.)
A
EXITING SHUTDOWN
ENTERING SHUTDOWN
V
SHDN
V
SHDN
5V/div
5V/div
V
IN_
V
IN_
1V/div
1V/div
V
V
OUT_
OUT_
500mV/div
500mV/div
40μs/div
20μs/div
/MAX9728B
Pin Description
PIN
NAME
FUNCTION
TQFN
TSSOP
1
2
3
4
C1P
PGND
C1N
Flying Capacitor Positive Terminal. Connect a 1µF ceramic capacitor from C1P to C1N.
Power Ground. Connect to SGND.
3
5
Flying Capacitor Negative Terminal. Connect a 1µF ceramic capacitor from C1P to C1N.
4
7
PV
Charge-Pump Output. Connect to SV and bypass with a 1µF ceramic capacitor to PGND.
SS
SS
5
8
SHDN
INL
Active-Low Shutdown Input
Left-Channel Input
6
9
7
10
11
12
14
1
SGND
INR
Signal Ground. Connect to PGND.
Right-Channel Input
8
9
SV
Amplifier Negative Supply. Connect to PV
Right-Channel Output
.
SS
SS
10
11
12
—
EP
OUTR
OUTL
Left-Channel Output
2
V
Positive Power-Supply Input. Bypass with a 1µF capacitor to PGND.
No Connection. Not internally connected.
DD
6,13
—
N.C.
EP
Exposed Paddle. Leave this connection floating or connect it to SV
.
SS
6
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
/MAX9728B
Detailed Description
V
DD
/2
OUT
The MAX9728A/MAX9728B stereo headphone ampli-
fiers feature Maxim’s DirectDrive architecture, eliminat-
ing the large output-coupling capacitors required by
conventional single-supply headphone amplifiers.
These devices consist of two 60mW Class AB head-
phone amplifiers, undervoltage lockout (UVLO)/shut-
down control, charge pump, and comprehensive
click-and-pop suppression circuitry (see the Functional
Diagram/Typical Operating Circuits). The charge pump
V
V
DD
V
DD
SGND
inverts the positive supply (V ), creating a negative
DD
supply (PV ). The headphone amplifiers operate from
SS
CONVENTIONAL DRIVER-BIASING SCHEME
these bipolar supplies with their outputs biased about
SGND (Figure 1). The benefit of this SGND bias is that
the amplifier outputs do not have a DC component. The
large DC-blocking capacitors required with convention-
al headphone amplifiers are unnecessary, conserving
board space, reducing system cost, and improving fre-
quency response. The MAX9728A/MAX9728B feature
an undervoltage lockout that prevents operation from
an insufficient power supply and click-and-pop sup-
pression that eliminates audible transients on startup
and shutdown. The MAX9728A/MAX9728B also feature
thermal-overload and short-circuit protection.
V
OUT
V
DD
SGND
2V
DD
-V
DD
DirectDrive
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typical-
ly half the supply) for maximum dynamic range. Large-
coupling capacitors are needed to block this DC bias
from the headphone. Without these capacitors, a signifi-
cant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
DirectDrive BIASING SCHEME
Figure 1. Conventional Driver Output Waveform vs.
MAX9728A/MAX9728B Output Waveform
Charge Pump
The MAX9728A/MAX9728B feature a low-noise charge
pump. The 270kHz switching frequency is well beyond
the audio range and does not interfere with audio sig-
nals. The switch drivers feature a controlled switching
speed that minimizes noise generated by turn-on and
turn-off transients. The di/dt noise caused by the para-
sitic bond wire and trace inductance is minimized by
limiting the switching speed of the charge pump.
Although not typically required, additional high-fre-
quency noise attenuation can be achieved by increas-
ing the value of C2 (see the Functional Diagram/Typical
Operating Circuits).
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage, allowing
the MAX9728A/MAX9728B outputs to be biased about
SGND. With no DC component, there is no need for the
large DC-blocking capacitors. The MAX9728A/
MAX9728B charge pumps require two small ceramic
capacitors, conserving board space, reducing cost,
and improving the frequency response of the head-
phone amplifier. See the Output Power vs. Load
Resistance and Charge-Pump Capacitor Size graph in
the Typical Operating Characteristics for details of the
possible capacitor sizes. There is a low DC voltage on
the amplifier outputs due to amplifier offset. However,
the offsets of the MAX9728A/MAX9728B are typically
1.5mV, which, when combined with a 32Ω load, results
in less than 47µA of DC current flow to the head-
phones.
Click-and-Pop Suppression
In conventional single-supply audio amplifiers, the out-
put-coupling capacitor contributes significantly to audi-
ble clicks and pops. Upon startup, the amplifier charges
the coupling capacitor to its bias voltage, typically half
the supply. Likewise, on shutdown, the capacitor is dis-
charged. This results in a DC shift across the capacitor,
which appears as an audible transient at the speaker.
_______________________________________________________________________________________
7
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Since the MAX9728A/MAX9728B do not require output-
coupling capacitors, this problem does not arise.
Additionally, the MAX9728A/MAX9728B feature exten-
sive click-and-pop suppression that eliminates any
audible transient sources internal to the device.
output, supply, and ground traces decrease θ , allow-
JA
ing more heat to be transferred from the package to the
surrounding air.
Thermal-overload protection limits total power dissipa-
tion in the MAX9728A/MAX9728B. When the junction
temperature exceeds +150°C, the thermal-protection
circuitry disables the amplifier output stage. The ampli-
fiers are enabled once the junction temperature cools
by approximately 12°C. This results in a pulsing output
under continuous thermal-overload conditions.
Typically, the output of the device driving the
MAX9728A/MAX9728B has a DC bias of half the supply
voltage. At startup, the input-coupling capacitor is
charged to the preamplifier’s DC-bias voltage through
the input and feedback resistors of the MAX9728A/
MAX9728B, resulting in a DC shift across the capacitor
and an audible click/pop. Delay the rise of SHDN 4 to 5
Output Dynamic Range
Dynamic range is the difference between the noise floor
of the system and the output level at 1% THD+N.
Determine the system’s dynamic range before setting
the maximum output gain. Output clipping occurs if the
output signal is greater than the dynamic range of the
system. The DirectDrive architecture of the MAX9728A/
MAX9728B has increased the dynamic range compared
to other single-supply amplifiers.
time constants based on R and C , relative to the
IN
IN
startup of the preamplifier, to eliminate clicks-and-pops
caused by the input filter.
Shutdown
The MAX9728A/MAX9728B feature a < 0.1µA, low-
power shutdown mode that reduces quiescent current
consumption and extends battery life for portable appli-
cations. Drive SHDN low to disable the amplifiers and
the charge pump. In shutdown mode, the amplifier out-
Maximum Output Swing
Internal device structures limit the maximum voltage
swing of the MAX9728A/MAX9728B. The output must
not be driven such that the peak output voltage exceeds
/MAX9728B
put impedance is set to 14kΩ||R (R is 30kΩ for the
F
F
MAX9728B). The amplifiers and charge pump are
enabled once SHDN is driven high.
the opposite supply voltage by 9V. For example, if V
DD
Applications Information
= 5V, the charge pump sets PV = -5V. Therefore, the
SS
peak output swing must be less than 4V to prevent
exceeding the absolute maximum ratings.
Power Dissipation
Under normal operating conditions, linear power ampli-
fiers can dissipate a significant amount of power. The
maximum power dissipation for each package is given
in the Absolute Maximum Ratings section under
Continuous Power Dissipation or can be calculated by
the following equation:
Component Selection
Input-Coupling Capacitor
The input capacitor (C ), in conjunction with the input
IN
resistor (R ), forms a highpass filter that removes the
IN
DC bias from an incoming signal (see the Functional
Diagram/Typical Operating Circuits). The AC-coupling
capacitor allows the device to bias the signal to an
optimum DC level. Assuming zero-source impedance,
the -3dB point of the highpass filter is given by:
T
− T
A
J(MAX)
P
=
DISSPKG(MAX)
θ
JA
where T
is +150°C, T is the ambient tempera-
A
J(MAX)
ture, and θ is the reciprocal of the derating factor in
JA
1
f
=
−3dB
°C/W as specified in the Absolute Maximum Ratings
2πR C
IN IN
section. For example, θ of the Thin QFN package is
JA
+68°C/W, and +110°C/W for the TSSOP package.
Choose the C such that f
is well below the lowest
-3dB
IN
-3dB
The MAX9728A/MAX9728B have two power dissipation
sources: a charge pump and the two output amplifiers.
If power dissipation for a given application exceeds the
maximum allowed for a particular package, reduce
frequency of interest. Setting f
too high affects the
device’s low-frequency response. Use capacitors
whose dielectrics have low-voltage coefficients, such
as tantalum or aluminum electrolytic. Capacitors with
high-voltage coefficients, such as ceramics, can result
in increased distortion at low frequencies.
V
, increase load impedance, decrease the ambient
DD
temperature, or add heatsinking to the device. Large
8
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
/MAX9728B
Charge-Pump Capacitor Selection
Use ceramic capacitors with a low ESR for optimum
performance. For optimal performance over the extend-
ed temperature range, select capacitors with an X7R
dielectric. Table 1 lists suggested manufacturers.
switching transients. Bypass V
value as C1, and place it physically close to the V
and PGND pins.
with C3, the same
DD
DD
Amplifier Gain
The gain of the MAX9728B amplifier is internally set to
-1.5V/V. All gain-setting resistors are integrated into the
device, reducing external component count. The inter-
nally set gain, in combination with DirectDrive, results in
a headphone amplifier that requires only five small
capacitors to complete the amplifier circuit: two for the
charge pump, two for audio input coupling, and one for
power-supply bypassing (see the Functional
Diagram/Typical Operating Circuits).
Flying Capacitor (C1)
The value of the flying capacitor (see the Functional
Diagram/Typical Operating Circuits) affects the charge
pump’s load regulation and output resistance. A C1
value that is too small degrades the device’s ability to
provide sufficient current drive, which leads to a loss of
output voltage. Increasing the value of C1 improves load
regulation and reduces the charge-pump output resis-
tance to an extent. See the Output Power vs. Load
Resistance and Charge-Pump Capacitor Size graph in
the Typical Operating Characteristics. Above 1µF, the
on-resistance of the switches and the ESR of C1 and C2
dominate.
The gain of the MAX9728A amplifier is set externally as
shown in Figure 2, the gain is:
A = -R /R (V/V)
V
F
IN
Choose feedback resistor values in the tens of kΩ
range. Lower values may cause excessive power dissi-
Hold Capacitor (C2)
The hold capacitor value (see the Functional
Diagram/Typical Operating Circuits) and ESR directly
pation and require impractically small values of R for
IN
large gain settings. The high-impedance state of the
outputs can also be degraded during shutdown mode if
an inadequate feedback resistor is used since the
equivalent output impedance during shutdown is
affect the ripple at PV . Increasing the value of C2
SS
reduces output ripple. Likewise, decreasing the ESR of
C2 reduces both ripple and output resistance. Lower
capacitance values can be used in systems with low
maximum output power levels. See the Output Power
vs. Load Resistance and Charge-Pump Capacitor Size
graph in the Typical Operating Characteristics.
14kΩ||R (R is equal to 30kΩ for the MAX9728B). The
F
F
source resistance of the input device may also need to
be taken into consideration. Since the effective value of
R
is equal to the sum of the source resistance of the
IN
input device and the value of the input resistor connect-
ed to the inverting terminal of the headphone amplifier
(20kΩ for the MAX9728B), the overall closed-loop gain
of the headphone amplifier can be reduced if the input
resistor is not significantly larger than the source resis-
tance of the input device.
Power-Supply Bypass Capacitor (C3)
The power-supply bypass capacitor (see the Functional
Diagram/Typical Operating Circuits) lowers the output
impedance of the power supply, and reduces the
impact of the MAX9728A/MAX9728Bs’ charge-pump
Table 1. Suggested Capacitor Manufacturers
SUPPLIER
PHONE
FAX
WEBSITE
www.t-yuden.com
Taiyo Yuden
800-348-2496
847-803-6100
770-436-1300
847-925-0899
847-390-4405
770-436-3030
TDK
www.component.tdk.com
www.murata.com
Murata
_______________________________________________________________________________________
9
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Lineout Amplifier and Filter Block
The MAX9728A can be used as an audio line driver
R
F
capable of providing 2V
gle 5V supply (see Figure 3 for the RMS Output Voltage
vs. Supply Voltage plot). 2V is a popular audio line
into 10kΩ loads with a sin-
RMS
RMS
level, first used in CD players, but now common in DVD
and set-top box (STB) interfacing standards. A 2V
MAX9728A
R
IN
LEFT
AUDIO
INPUT
RMS
INL
sinusoidal signal equates to approximately 5.7V
,
P-P
OUTL
which means that the audio system designer cannot
simply run the lineout stage from a (typically common)
5V supply—the resulting output swing would be inade-
quate. A common solution to this problem is to use op
amps driven from split supplies ( 5V typically), or to use
a high-voltage supply rail (9V to 12V). This can mean
adding extra cost and complexity to the system power
supply to meet this output level requirement. Having the
OUTR
R
RIGHT
AUDIO
INPUT
IN
INR
ability to derive 2V
from a 5V supply can often sim-
RMS
plify power-supply design in some systems.
When the MAX9728A is used as a line driver to provide
outputs that feed stereo equipment (receivers, STBs,
notebooks, and desktops) with a digital-to-analog con-
verter (DAC) used as an audio input source, it is often
desirable to eliminate any high-frequency quantization
noise produced by the DAC output before it reaches
the load. This high-frequency noise can cause the input
stages of the line-in equipment to exceed slew-rate lim-
itations or create excessive EMI emissions on the
cables between devices.
R
F
Figure 2. Gain Setting for the MAX9728A
/MAX9728B
RMS OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
4.1
f
IN
= 1kHz
To suppress this noise, and to provide a 2V
stan-
RMS
3.9
3.7
3.5
3.3
3.1
2.9
2.7
2.5
dard audio output level from a single 5V supply, the
MAX9728A can be configured as a line driver and
active lowpass filter. Figure 4 shows the MAX9728A
connected as 2-pole Rauch/multiple feedback filter with
a passband gain of 6dB and a -3dB (below passband)
cutoff frequency of approximately 27kHz (see Figure 5
for the Gain vs. Frequency plot).
R = 10kΩ
L
1% THD+N
R = 1kΩ
L
1% THD+N
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Connect PGND and SGND together at a
single point on the PC board. Connect PV
to SV
SS
4.5
5.0
SUPPLY VOLTAGE (V)
5.5
SS
and bypass with a 1µF capacitor. Place the power-sup-
ply bypass capacitor and the charge-pump hold
capacitor as close to the MAX9728 as possible. Route
PGND and all traces that carry switching transients
away from SGND and the audio signal path. The thin
QFN package features an exposed paddle that
improves thermal efficiency. Ensure that the exposed
paddle is electrically isolated from PGND, SGND,
Figure 3. RMS Output Voltage vs. Supply Voltage
and V . Connect the exposed paddle to SV only
DD
SS
when the board layout dictates that the exposed
paddle cannot be left floating.
10 ______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
/MAX9728B
15kΩ
220pF
LEFT
AUDIO
INPUT
1μF
MAX9728A
7.5kΩ
1.2nF
7.5kΩ
INL
LINE-IN DEVICE
OUTL
STEREO
DAC
10kΩ
1.2nF
7.5kΩ
RIGHT
AUDIO
INPUT
OUTR
1μF
7.5kΩ
INR
10kΩ
220pF
15kΩ
Figure 4. MAX9728A Line-Out Amplifier and Filter Block Configuration
MAX9728A ACTIVE FILTER GAIN
vs. FREQUENCY
10
R = 10kΩ
L
5
0
-5
-10
-15
-20
-25
-30
-35
1k
10k
100k
1M
FREQUENCY (Hz)
Figure 5. Frequency Response of Active Filter of Figure 4
______________________________________________________________________________________ 11
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
System Diagram
V
DD
0.1μF
15kΩ
1μF
15kΩ
INR
OUTR+
OUTR-
V
DD
PV
DD
BIAS
1μF
MAX9710
GND
PGND
MUTE
SHDN
INL
OUTL-
OUTL+
0.1μF
15kΩ
V
DD
15kΩ
μCONTROLLER
/MAX9728B
100kΩ
100kΩ
0.1μF
STEREO
DAC
OUTL
SHDN
O.47μF
O.47μF
MAX9728B
OUTR
SGND
INL
INR
PV
PGND
V
DD
SS
SV
V
SS
C1P
DD
C1N
1μF
1μF
1μF
12 ______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
/MAX9728B
Functional Diagram/Typical Operating Circuits
4.5V TO 5.5V
C
IN
0.47μF
R
R
IN*
F*
LEFT
AUDIO
INPUT
20kΩ
30kΩ
ON
C3
1μF
OFF
12
5
6
(9)
(2)
(8)
INL
V
DD
SHDN
V
DD
11
(1)
OUTL
HEADPHONE
JACK
1
(3)
SV
SS
C1P
UVLO/
SHUTDOWN
CONTROL
CLICK-AND-POP
SUPPRESSION
CHARGE
PUMP
SGND
C1
1μF
V
DD
3
10
(14)
(5) C1N
OUTR
MAX9728A
SV
SS
PV
SV
9
(12)
PGND
SS
SGND
SS
INR
4
7
(10)
2
(4)
8
(11)
(7)
C
IN
R *
20kΩ
R *
30kΩ
IN
F
C2
1μF
0.47μF
RIGHT
AUDIO
INPUT
*R AND R VALUES ARE CHOSEN FOR A GAIN -1.5V/V.
IN
F
( ) TSSOP PACKAGE
______________________________________________________________________________________ 13
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Functional Diagram/Typical Operating Circuits (continued)
4.5V TO 5.5V
C
IN
0.47μF
LEFT
AUDIO
INPUT
ON
C3
1μF
OFF
12
5
6
(9)
(2)
(8)
V
DD
INL
SHDN
R
F*
30kΩ
V
DD
R
IN*
20kΩ
11
(1)
OUTL
HEADPHONE
JACK
1
(3)
V
SS
C1P
UVLO/
SHUTDOWN
CONTROL
CLICK-AND-POP
SUPPRESSION
/MAX9728B
CHARGE
PUMP
SGND
C1
1μF
V
DD
3
10
(14)
(5) C1N
OUTR
R
IN
20kΩ
MAX9728B
SV
SS
R
F
30kΩ
SV
9
(12) (4)
PV
INR
8
(11)
SS PGND
SGND
SS
4
2
7
(10)
(7)
C2
1μF
C
IN
0.47μF
RIGHT
AUDIO
INPUT
( ) TSSOP PACKAGE
14 ______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
/MAX9728B
Pin Configurations
TOP VIEW
TOP VIEW
9
8
7
+
OUTL
1
2
3
4
5
6
7
14 OUTR
13 N.C.
V
DD
10
OUTR
6
5
INL
C1P
PGND
C1N
12 SV
SS
MAX9728A
MAX9728B
11 INR
OUTL 11
MAX9728A
MAX9728B
SHDN
10 SGND
V
DD 12
PV
SS
4
N.C.
9
8
INL
+
PV
SS
SHDN
1
2
3
TSSOP
TQFN
Chip Information
TRANSISTOR COUNT: 993
PROCESS: BiCMOS
______________________________________________________________________________________ 15
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to
the package regardless of RoHS status.
PACKAGE TYPE
12 TQFN-EP
14 TSSOP
PACKAGE CODE
T1233-1
DOCUMENT NO.
21-0136
U14-1
21-0066
(NE - 1)
X e
MARKING
E
E/2
D2/2
(ND - 1)
e
X e
D/2
AAAA
C
D2
D
L
k
b
0.10 M
C A B
/MAX9728B
C
L
E2/2
L
E2
C
L
C
L
0.10
C
0.08
A
C
A2
A1
L
L
e
e
PACKAGE OUTLINE
8, 12, 16L THIN QFN, 3x3x0.8mm
1
21-0136
I
2
16 ______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
/MAX9728B
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to
the package regardless of RoHS status.
PKG
8L 3x3
12L 3x3
16L 3x3
EXPOSED PAD VARIATIONS
REF. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX.
D2
E2
PKG.
PIN ID
JEDEC
CODES
A
b
0.70 0.75 0.80 0.70 0.75 0.80
0.25 0.30 0.35 0.20 0.25 0.30
0.70 0.75 0.80
0.20 0.25 0.30
MIN.
0.25
0.95
0.95
0.95
0.95
0.65
0.65
0.95
0.95
NOM. MAX.
MIN.
0.25
0.95
0.95
0.95
NOM. MAX.
TQ833-1
T1233-1
T1233-3
0.70
1.10
1.10
1.10
1.25
1.25
1.25
0.70
1.10
1.10
1.10
1.10
0.80
0.80
1.10
1.10
1.25
1.25
1.25
1.25
1.25
0.95
0.95
0.35 x 45°
0.35 x 45°
0.35 x 45°
0.35 x 45°
0.35 x 45°
0.225 x 45°
0.225 x 45°
0.35 x 45°
0.35 x 45°
WEEC
D
2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10
2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10
WEED-1
WEED-1
WEED-1
WEED-2
WEED-2
WEED-2
WEED-2
WEED-2
E
e
0.65 BSC.
0.50 BSC.
0.50 BSC.
T1233-4
T1633-2
1.25
1.25
0.95
0.95
1.25
1.25
L
0.35 0.55 0.75 0.45 0.55 0.65 0.30 0.40 0.50
1.10
0.80
0.80
1.10
0.95
0.65
0.65
0.95
N
ND
NE
A1
A2
k
8
12
16
T1633F-3
T1633FH-3
T1633-4
2
3
4
2
3
4
1.25
1.25
0
0.02 0.05
0
0.02 0.05
0
0.02 0.05
T1633-5
1.10
0.95
0.20 REF
0.20 REF
0.20 REF
-
-
-
-
-
-
0.25
0.25
0.25
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO
JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED
WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS
9. DRAWING CONFORMS TO JEDEC MO220 REVISION C.
.
10. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
11. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY.
12. WARPAGE NOT TO EXCEED 0.10mm.
PACKAGE OUTLINE
8, 12, 16L THIN QFN, 3x3x0.8mm
2
21-0136
I
2
______________________________________________________________________________________ 17
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to
the package regardless of RoHS status.
/MAX9728B
18 ______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
/MAX9728B
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
1/06
Initial release
Corrected top mark designations
—
1
7/09
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 ____________________ 19
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
相关型号：
MAX9728AEUD+T
Audio Amplifier, 0.063W, 2 Channel(s), 1 Func, BICMOS, PDSO14, 5 X 4.40 MM, 1.10 MM HEIGHT, LEAD FREE, MO-153AB-1, TSSOP-14
MAXIM
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