General Description
The MAX13330/MAX13331 stereo headphone amplifiers
are designed for automotive applications requiring out-
put short-circuit and ESD protection to battery/ground
with diagnostics. These devices use Maxim’s unique
DirectDrive®architecture to produce a ground-refer-
enced output from a single supply, eliminating the need
for large DC-blocking capacitors, saving board space
and component height. The gain of the amplifier is set
internally (-1.5V/V) on the MAX13330 or adjusted exter-
nally with resistors on the MAX13331.
The MAX13330/MAX13331 deliver 120mW per channel
into a 16Ωload or 135mW into a 32Ωload and have a
low 0.01% THD+N. Low output impedance and the effi-
cient integrated charge pump allows the device to drive
loads as low as 8Ω, enabling the use of small loud-
speakers. An 80dB at 217Hz PSRR allows these
devices to operate from noisy digital supplies without
an additional linear regulator. These devices include
±15kV Human Body Model ESD protection and short-
circuit protection up to +45V at the headphone outputs.
Comprehensive click-and-pop circuitry suppresses
audible clicks and pops on startup and shutdown. A
low-power shutdown mode reduces the supply current
to 3µA (typ).
The MAX13330/MAX13331 are specified from -40°C to
+105°C AEC-Q100 Level 2 automotive temperature
range and are available in a 16-pin QSOP package.
Applications
Automotive Entertainment Systems
Automotive Rear Seat Entertainment Systems
Features
♦4V to 5.5V Single-Supply Operation
♦2MHz Charge Pump Prevents AM Radio
Interference
♦Ground-Referenced Outputs Eliminate Bulky DC-
Blocking Capacitors
♦Short-to-Ground and Battery (VBAT up to +45V)
Output Protection, Load Dump Protection
♦Short-Circuit Diagnostic Output
♦Adjustable Gain (MAX13331) or Fixed -1.5V/V Gain
(MAX13330)
♦125mW per Channel into 32Ωat 0.01% THD+N
♦Integrated Click-and-Pop Suppression
♦High PSRR Eliminates LDO
♦No Degradation of Low-Frequency Response Due
to Output Capacitors
♦±15kV Human Body Model ESD Protection for
Output Pins
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
________________________________________________________________
Maxim Integrated Products
1
MAX13330
MAX13331
OUTR
VSS
PGND
OUTL
13
14
15
16
4
3
2
1
SGND
DIAG
125
VDD
INR
SGND
INL
QSOP
+
PGND
C1N
CPVSS
9
10
11
8
7
6
C1P
CPVDD
SHDN
Pin Configuration
CLICK-AND-POP
SUPPRESSION
OUTPUT PROTECTION & DIAGNOSTICS
RIGHT-CHANNEL
AUDIO IN
LEFT-CHANNEL
AUDIO IN
MAX13330
DIAGNOSTICS
OUTPUT
SHDN
Simplified Block Diagram
19-4341; Rev 3; 7/11
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.
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
Ordering Information
/V denotes an automotive qualified part.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Typical Application Circuits appear at end of data sheet.
PART GAIN TEMP
RANGE
PIN-
PACKAGE
MAX13330GEE/V+T -1.5V/V -40°C to +105°C 16 QSOP
MAX13331GEE/V+T Externally
Set -40°C to +105°C 16 QSOP
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD = VCPVDD = +5V, VSGND = VPGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL= ∞, resistive load referenced to ground, for
MAX13330 gain = -1.5V/V (internally set), for MAX13331 gain = -1.5V/V (RIN = 30kΩ, RFB = 45kΩ), TA= TJ= -40°C to +105°C, unless
otherwise noted. Typical values are at TA= +25°C, unless otherwise noted.) (Note 2)
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.
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, refer to www.maxim-ic.com/thermal-tutorial.
VDD, CPVDD to SGND..............................................-0.3V to +6V
VSS, CPVSS to SGND ...............................................+0.3V to -6V
VDD, CPVDD..........................................................-0.3V to +0.3V
VSS, CPVSS ...........................................................-0.3V to +0.3V
SHDN, DIAG to SGND................................-0.3V to (VDD + 0.3V)
OUT_ to PGND.......................................(VCPVSS - 0.3V) to +45V
IN_ to SGND (MAX13330)................(VSS - 0.3V) to (VDD + 0.3V)
IN_ to SGND (MAX13331)..........................-0.3V to (VDD + 0.3V)
C1P to PGND........................................-0.3V to (VCPVDD + 0.3V)
C1N to PGND..............................................(VSS - 0.3V) to +0.3V
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA= +70°C)
QSOP (derate 9.6mW/°C above +70°C))..................771.5mW
Operating Temperature Range .........................-40°C to +105°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
PACKAGE THERMAL CHARACTERISTICS (Note 1)
QSOP
Junction-to-Ambient Thermal Resistance (θJA) ......103.7°C/W
Junction-to-Case Thermal Resistance (θJC) ................37°C/W
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
GENERAL
Amplifier Supply Voltage Range VDD 4.0 5.5 V
Charge-Pump Supply Voltage
Range VCPVDD 4.0 5.5 V
Charge-Pump Output Voltage VCPVSS -VDD V
Quiescent Supply Current IDD RL = 10 mA
Shutdown Supply Current ISHDN 10 μA
SHDN Input-Logic High VIH 2 V
SHDN Input-Logic Low VIL 0.8 V
SHDN Input Leakage Current -1 +1 μA
SHDN to Full Operation Time tSON 100 μs
DIAGNOSTICS
No fault 0.02 x
VDD
OUTR short to
SGND
0.22 x
VDD
0.25 x
VDD
0.28 x
VDD
OUTL short to
SGND
0.47 x
VDD
0.50 x
VDD
0.53 x
VDD
OUTR short to
VBAT
0.72 x
VDD
0.75 x
VDD
0.78 x
VDD
Diagnostic Output Voltage VDIAG RDIAG = ,
TA = +25°C
OUTL short to
VBAT
0.97 x
VDD
V
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VDD = VCPVDD = +5V, VSGND = VPGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL= ∞, resistive load referenced to ground, for
MAX13330 gain = -1.5V/V (internally set), for MAX13331 gain = -1.5V/V (RIN = 30kΩ, RFB = 45kΩ), TA= TJ= -40°C to +105°C, unless
otherwise noted. Typical values are at TA= +25°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Short-to-SGND Threshold 130 mA
Short-to-VBAT Threshold 130 mA
AMPLIFIERS
Voltage Gain AV MAX13330 -1.48 -1.5 -1.52 V/V
Gain Matching MAX13330 ±0.2 %
Input Offset Voltage ±1 ±6 mV
Input Bias Current VIN_ = 0V 50 nA
Input Impedance RIN MAX13330 20 30 k
DC, VDD = 4.0V to 5.5V, input referred -86
Power-Supply Rejection Ratio PSRR f =1kHz, VRIPPLE = 100mVP-P -80
dB
RL = 8 75
RL = 16 120
Output Power Per Channel POUT_
THD+N = 1%;
VDD = VCPVDD = 5V;
fIN = 1kHz RL = 32 135
mW
Output Voltage VOUT_ R
L = 1k 2 VRMS
Output Impedance in Shutdown 14 k
RL = 16, POUT = 100mW, f = 1kHz 0.03 %
Total Harmonic Distortion Plus
Noise THD+N RL = 32, POUT = 125mW, f = 1kHz 0.01 %
Signal-to-Noise Ratio SNR RL = 32, POUT = 135mW, f = 22Hz to 22kHz 100 dB
Noise Vnf = 22Hz to 22kHz bandwidth; inputs
AC-coupled to grounded 6 μVRMS
Slew Rate SR 0.3 V/μs
Maximum Capacitive Load CL No sustained oscillation 3000 pF
Into shutdown -80
Click-and-Pop Level KCP
Peak voltage, TA =
+25°C, A-weighted,
32 samples per
second; Inputs AC-
coupled to ground Out of shutdown -60
dB
Charge-Pump Oscillator
Frequency fOSC 1.9 2.2 2.5 MHz
Crosstalk RL = 32, VIN = 200mVP-P, f = 10kHz -75 dB
Thermal-Shutdown Temperature +155 °C
Thermal-Shutdown Hysteresis 10 °C
ESD Protection Human Body Model (OUTR and OUTL) ±15 kV
Note 2: All devices are 100% tested at TA= +25°C; specifications over temperature limits are guaranteed by design and QA
sampling.
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
4 _______________________________________________________________________________________
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc01
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 4V
RL = 8Ω
POUT = 25mW
POUT = 45mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc02
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 5V
RL = 8Ω
POUT = 25mW
POUT = 60mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc03
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 4V
RL = 16Ω
POUT = 25mW
POUT = 75mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc04
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 5V
RL = 16Ω
POUT = 50mW
POUT = 100mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc05
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 4V
RL = 32Ω
POUT = 25mW
POUT = 70mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc06
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.01
0.1
1
0.001
0.01 100
VDD = 5V
RL = 32Ω
POUT = 50mW
POUT = 125mW
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc07
OUTPUT POWER (mW)
THD+N (%)
5025
0.1
1
10
0.01
0 75
VDD = 4V
RL = 8Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc08
OUTPUT POWER (mW)
THD+N (%)
50 10025 75
0.1
1
10
0.01
0 125
VDD = 5V
RL = 8Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc09
OUTPUT POWER (mW)
THD+N (%)
50 10025 75
0.01
0.1
1
10
0.001
0 125
VDD = 4V
RL = 16Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
Typical Operating Characteristics
(VDD = VCPVDD = 5V, VSGND = VPGND = 0V, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz,
TA= +25°C, unless otherwise noted.)
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
_______________________________________________________________________________________ 5
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc10
OUTPUT POWER (mW)
THD+N (%)
12550 15025
0.01
0.1
1
10
0.001
0 10075 175
VDD = 5V
RL = 16Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc11
OUTPUT POWER (mW)
THD+N (%)
50 10025 75
0.01
0.1
1
10
0.001
0 125
VDD = 4V
RL = 32Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX13330/31 toc12
OUTPUT POWER (mW)
THD+N (%)
12550 15025
0.01
0.1
1
10
0.001
0 10075 175
VDD = 5V
RL = 32Ω
fIN = 10kHz
fIN = 1kHz
fIN = 100Hz
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX13330/31 toc13
FREQUENCY (kHz)
THD+N (%)
0.1 1 10
0.001
0.01
0.1
1
0.0001
0.01 100
VDD = 5V
RL = 1kΩ
VOUT_ = 2VRMS
VOUT_ = 1VRMS
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX13330/31 toc14
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
5.254.754.50 5.004.25
60
120
180
40
100
160
20
80
140
0
4.00 5.50
fIN = 1kHz
1% THD+N
RL = 32Ω
RL = 16Ω
RL = 8Ω
OUTPUT POWER vs. LOAD RESISTANCE
MAX13330/31 toc15
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
10 100
60
120
200
40
100
160
180
20
80
140
0
0 1000
fIN = 1kHz
10% THD+N
VDD = 4V
1% THD+N
VDD = 4V
1% THD+N
VDD = 5V
10% THD+N
VDD = 5V
POWER DISSIPATION vs.
OUTPUT POWER PER CHANNEL
MAX13330/31 toc16
OUTPUT POWER PER CHANNEL (mW)
POWER DISSIPATION (mW)
1006040 8020
300
600
800
200
500
100
400
700
0
0 120
VDD = 4V
fIN = 1kHz
RL = 32Ω
RL = 16Ω
RL = 8Ω
POWER DISSIPATION vs.
OUTPUT POWER PER CHANNEL
MAX13330/31 toc17
OUTPUT POWER PER CHANNEL (mW)
POWER DISSIPATION (mW)
80 14060 120 16020 10040
400
800
1200
200
600
1000
0
0 180
VDD = 5V
fIN = 1kHz
RL = 32Ω
RL = 16Ω
RL = 8Ω
Typical Operating Characteristics (continued)
(VDD = VCPVDD = 5V, VSGND = VPGND = 0V, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz,
TA= +25°C, unless otherwise noted.)
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
6 _______________________________________________________________________________________
CROSSTALK vs. FREQUENCY
MAX13330/31 toc19
FREQUENCY (kHz)
CROSSTALK (dB)
0.1 1 10
-80
-60
-40
-90
-70
-50
-100
0.01 100
VIN = 200mVP-P
RL = 32Ω
RIGHT TO LEFT
LEFT TO RIGHT
GAIN FLATNESS vs. FREQUENCY
MAX13330/31 toc20
FREQUENCY (kHz)
GAIN (dB)
1000.1 101
3.2
3.4
3.5
3.1
3.3
3.0
0.01 1000
MAX13330
VIN = 100mVP-P
OUTL
OUTR
Typical Operating Characteristics (continued)
(VDD = VCPVDD = 5V, VSGND = VPGND = 0V, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz,
TA= +25°C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX13330/31 toc18
FREQUENCY (kHz)
PSRR (dB)
100.1 1
-100
-40
-110
-80
-60
-50
-90
-70
-120
0.01 100
VDD = 5V
OUTR
VDD = 5V
OUTL
VRIPPLE = 100mVP-P
RL = 32Ω
VDD = 4V
OUTR
VDD = 4V
OUTL
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX13330/31 toc22
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.254.75 5.004.50
5
7
10
2
1
6
9
4
3
8
0
4.00 4.25 5.50
SUPPLY CURRENT vs. TEMPERATURE
MAX13330/31 toc23
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
075-25 100
6
10
12
4
2
8
0
-50 5025 125
OUTPUT FFT
MAX13330/31 toc21
FREQUENCY (kHz)
AMPLITUDE (dBV)
10 15
RL = 32Ω
-40
-20
0
-100
-120
-60
-80
-140
05 20
SHUTDOWN CURRENT vs. SUPPLY VOLTAGE
MAX13330/31 toc25
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (μA)
5.004.25 4.754.50
4
5
3
2
1
0
4.00 5.25 5.50
EXITING SHUTDOWN TRANSIENT
MAX13330/31 toc26
200
μ
s/div
VOUTL
1V/div
VOUTR
1V/div
VSHDN
5V/div
SHUTDOWN CURRENT vs. TEMPERATURE
MAX13330/31 toc24
TEMPERATURE (°C)
SHUTDOWN CURRENT (μA)
075-25 100
2.0
3.5
4.0
1.5
1.0
3.0
0.5
2.5
0
-50 5025 125
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
_______________________________________________________________________________________ 7
Pin Description
Typical Operating Characteristics (continued)
(VDD = VCPVDD = 5V, VSGND = VPGND = 0V, C1 = C2 = 1µF, RL= ∞, gain = -1.5V/V, THD+N measurement bandwidth = 22Hz to 22kHz,
TA= +25°C, unless otherwise noted.)
PIN NAME FUNCTION
1 INL Inverting Left-Channel Audio Input
2, 4 SGND Amplifier Signal Ground. The noninverting inputs of the amplifiers are connected to the amplifier
signal ground. Connect both to the signal ground plane.
3 INR Inverting Right-Channel Audio Input
5V
DD Amplifier Positive-Power Supply. Connect to positive supply. Bypass with a 1µF capacitor to
SGND as close to the pin as possible.
6SHDN Active-Low Shutdown Input
7 CPVDD Charge-Pump Power Supply. Powers charge-pump inverter, charge-pump logic, and oscillator.
Connect to positive supply. Bypass with a 1µF capacitor to PGND as close to the pin as possible.
8 C1P Flying-Capacitor Positive Terminal. Connect a 1µF capacitor between C1P and C1N.
9, 15 PGND Power Ground. Connect both to the power ground plane.
10 C1N Flying-Capacitor Negative Terminal. Connect a 1µF capacitor between C1P and C1N.
11 CPVSS Charge-Pump Output. Connect to VSS and bypass with a 1µF capacitor to PGND.
12 DIAG Diagnostic Voltage Output
13 OUTR Right-Channel Output
14 VSS Amplifier Negative Power Supply. Connect to CPVSS.
16 OUTL Left-Channel Output
ENTERING SHUTDOWN TRANSIENT
MAX13330/31 toc27
200
μ
s/div
VOUTL
1V/div
VOUTR
1V/div
VSHDN
5V/div
POWER-UP/-DOWN TRANSIENT
MAX13330/31 toc28
10ms/div
VOUTL
1V/div
VOUTR
1V/div
VSHDN
5V/div
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
8 _______________________________________________________________________________________
Detailed Description
The MAX13330/MAX13331 headphone amplifiers fea-
ture Maxim’s DirectDrive architecture, eliminating the
large output-coupling capacitors required by conven-
tional single-supply headphone amplifiers. The devices
consists of two Class AB headphone amplifiers, under-
voltage lockout (UVLO), low-power shutdown control,
comprehensive click-and-pop suppression, output
short-circuit/ESD protection and output short-circuit
diagnostics.
These devices can drive loads as low as 8Ω, and deliv-
er up to 120mW per channel into 16Ωand 135mW into
32Ω. The MAX13330 features a fixed gain of -1.5V/V,
and the MAX13331 features a programmable gain con-
figured with external resistors. The headphone outputs
feature ±15kV Human Body Model ESD protection, and
enhanced short-circuit protection to ground or battery
(VBAT up to +45V). An integrated short-circuit diagnos-
tic output provides the status of the MAX13330/
MAX13331 during operation as a fraction of the analog
supply voltage.
DirectDrive
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typi-
cally half the supply) for maximum dynamic range.
Large coupling capacitors are needed to block this DC
bias from the headphone. Without these capacitors, a
significant amount of DC current flows to the head-
phone, resulting in unnecessary power dissipation and
possible damage to both the headphone and the head-
phone amplifier.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative-supply voltage, allowing
the MAX13330/MAX13331 outputs to be biased about
SGND (Figure 1). With no DC component, there is no
need for the large DC-blocking capacitors. Instead of
two large (220µF, typ) tantalum capacitors, the
MAX13330/MAX13331 charge pump requires two small
ceramic capacitors, conserving board space, reducing
cost, and improving the frequency response of the
headphone amplifier. See the Output Power vs. Load
Resistance graph in the
Typical Operating
Characteristics
for details of the possible capacitor
sizes. There is a low DC voltage on the amplifier out-
puts due to amplifier offset. However, the output offset
of the MAX13330 is typically ±2.5mV which, when com-
bined with a 32Ωload, results in less than ±78µA of DC
current flow to the headphones. Previous attempts to
eliminate the output-coupling capacitors involved bias-
ing the headphone return (sleeve) to the DC-bias volt-
age of the headphone amplifiers.
This method raises some issues:
• The sleeve is typically grounded to the chassis.
Using this biasing approach, the sleeve must be
isolated from system ground, complicating product
design.
• During an ESD strike, the amplifier’s ESD structures
are the only path to system ground. Thus, the ampli-
fier must be able to withstand the full ESD strike.
• When using the headphone jack as a line out to
other equipment, the bias voltage on the sleeve
may conflict with the ground potential from other
equipment, resulting in possible damage to the
amplifiers.
VDD
VSS
GND
VOUT
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
VDD/2
VDD
GND
VOUT
Figure 1. Conventional Driver Output Waveform vs. MAX13330/
MAX13331 Output Waveform
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
_______________________________________________________________________________________ 9
Low-Frequency Response
In addition to the cost and size disadvantages of the DC-
blocking capacitors required by conventional head-
phone amplifiers, these capacitors limit the amplifier’s
low-frequency response and can distort the audio signal:
1) The impedance of the headphone load and the DC-
blocking capacitor form a highpass filter with the -3dB
point set by:
where RLis the impedance of the headphone and
COUT is the value of the DC-blocking capacitor. The
highpass filter is required by conventional single-
ended, single power-supply headphone amplifiers to
block the midrail DC-bias component of the audio sig-
nal from the headphones. The drawback to the filter is
that it can attenuate low-frequency signals. Larger val-
ues of COUT reduce this effect but result in physically
larger, more expensive capacitors. Figure 2 shows the
relationship between the size of COUT and the resulting
low-frequency attenuation. Note that the -3dB point for
a 16Ωheadphone with a 100µF blocking capacitor is
100Hz, well within the normal audio band, resulting in
low-frequency attenuation of the reproduced signal.
2) The voltage coefficient of the DC-blocking capacitor
contributes distortion to the reproduced audio signal as
the capacitance value varies and the function of the
voltage across the capacitor changes. The reactance
of the capacitor dominates at frequencies below the
-3dB point and the voltage coefficient appears as fre-
quency-dependent distortion. Figure 3 shows the
THD+N introduced by two different capacitor dielectric
types. Note that below 100Hz, THD+N increases rapid-
ly. The combination of low-frequency attenuation and
frequency-dependent distortion compromises audio
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as in multimedia lap-
tops, MP3, CD, and DVD players. By eliminating the
DC-blocking capacitors through DirectDrive technolo-
gy, these capacitor-related deficiencies are eliminated.
Charge Pump
The MAX13330/MAX13331 feature a low-noise charge
pump. The 2.2MHz (typ) switching frequency is well
beyond the audio range. It does not interfere with the
audio signals and avoids AM band interference. The
switch drivers feature a controlled switching speed that
minimizes noise generated by turn-on and turn-off tran-
sients. By limiting the switching speed of the charge
pump, the di/dt noise caused by the parasitic bond
wire and trace inductance is minimized. Although not
typically required, additional high-frequency noise
attenuation can be achieved by increasing the value of
C2 (see the
Typical Application Circuits
).
fRC Hz
dB LOUT
−=××
()
3
1
2π
0
-30
10 100 1k 10k 100k
LOW-FREQUENCY ROLLOFF
(RL = 16Ω)
-24
-27
-12
-15
-18
-21
-6
-9
-3
FREQUENCY (Hz)
ATTENUATION (dB)
DirectDrive
330μF
220μF
100μF
33μF
Figure 2. Low-Frequency Attenuation for Common DC-Blocking
Capacitor Values
ADDITIONAL THD+N DUE
TO DC-BLOCKING CAPACITORS
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.001
0.01
0.1
1
10
0.0001
10 100k
TANTALUM
ALUM/ELEC
Figure 3. Distortion Contributed by DC-Blocking Capacitors
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
10 ______________________________________________________________________________________
Diagnostic Output
The MAX13330/MAX13331 provides an analog diag-
nostic output as a fraction of the analog supply voltage
VDD. The voltage at DIAG will correspond to the fault
condition with the highest priority that is present in the
system, as shown in Table 1. When simultaneous fault
conditions occur on both headphone outputs, the diag-
nostic output will only report the fault condition at OUTR
until it is cleared or removed. Only then will the fault
condition at OUTL be reported at DIAG. Connect DIAG
to a high-impedance input.
For both headphone outputs, short circuits to VBAT are
dynamic and VDIAG will be automatically cleared as
soon as the fault condition is removed. Short circuits to
GND occurring when a positive output voltage is pre-
sent on OUTL or OUTR, will result in VDIAG being
latched until the fault condition is cleared.
When VDIAG is latched, it can be cleared by either tog-
gling SHDN low for less than 5µs or initiating a full reset
of the MAX13330/MAX13331. Toggling SHDN low for
less than 5µs will cause the fault to ground to be
cleared without shutting down the device or interrupting
the output state of the amplifiers. A full reset requires
SHDN to be pulled low for more than 50µs. The amplifi-
er outputs will enter high impedance and remain in that
state until the device exits shutdown.
Click-and-Pop Suppression
In conventional single-supply audio amplifiers, the out-
put-coupling capacitor is a major contributor of audible
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 to SGND. This results in a DC shift across the
capacitor which appears as an audible transient at the
speaker. Since the MAX13330/MAX13331 does not
require output-coupling capacitors, this problem does
not arise.
Additionally, the MAX13330/MAX13331 feature exten-
sive click-and-pop suppression that eliminates any
audible transient sources internal to the device. The
Power-Up/-Down Transient graph in the
Typical
Operating Characteristic
s shows that there is minimal
DC shift and no spurious transients at the output upon
startup or shutdown.
In most applications, the output of the preamplifier dri-
ving the MAX13330/MAX13331 has a DC bias of typi-
cally half the supply. At startup, the input-coupling
capacitor is charged to the preamplifier’s DC-bias volt-
age through the feedback resistor of the MAX13330/
MAX13331, resulting in a DC shift across the capacitor
and an audible click/pop. Delaying the rise of SHDN 4
to 5 time constants (80ms to 100ms) based on RIN and
CIN relative to the startup of the preamplifier, eliminates
this click/pop caused by the input filter.
Shutdown
The MAX13330/MAX13331 feature shutdown control
allowing audio signals to be shut down or muted.
Driving SHDN low disables the amplifiers and the
charge pump, sets the amplifier output impedance to
14kΩ(typ), and reduces the supply current. In shut-
down mode, the supply current is reduced to 2µA. The
charge pump is enabled once SHDN is driven high.
Applications Information
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 contin-
uous power dissipation or can be calculated by the
following equation:
where TJ(MAX) is +145°C, TAis the ambient tempera-
ture, and θJA is the reciprocal of the derating factor in
°C/W as specified in the
Absolute Maximum Ratings
section. The thermal resistance θJA of the QSOP pack-
age is 120°C/W.
The MAX13330/MAX13331 have two power dissipation
sources: the charge pump and two amplifiers. If power
dissipation for a given application exceeds the maxi-
mum allowed for a particular package, either reduce
VDD, increase load impedance, decrease the ambient
temperature, or add heatsinking to the device. Large
output, supply, and ground traces improve the maxi-
mum power dissipation in the package.
PTT
DISSPKG MAX JMAX A
JA
() ()
()
=−
θ
VDIAG STATE PRIORITY
VDD OUTL Short to VBAT 3
3/4 VDD OUTR Short to VBAT 1
1/2 VDD OUTL Short to SGND 4
1/4 VDD OUTR Short to SGND 2
0 No Fault 5
Three State Shutdown —
Table 1. MAX13330/MAX13331 Diagnostic
Priority
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
______________________________________________________________________________________ 11
Thermal-overload protection limits total power dissipa-
tion in the MAX13330/MAX13331. When the junction
temperature exceeds +145°C (typ), the thermal-protec-
tion circuitry disables the amplifier output stage. The
amplifiers are enabled once the junction temperature
cools by 5°C. This results in a pulsing output under
continuous thermal-overload conditions.
Output Power
The device has been specified for the worst-case sce-
nario, when both inputs are in-phase. Under this condi-
tion, the amplifiers simultaneously draw current from the
charge pump, leading to a proportional reduction in
VSS headroom. In typical stereo audio applications, the
left and right signals have differences in both magni-
tude and phase, subsequently leading to an increase in
the maximum attainable output power. Figure 4 shows
the two extreme cases for in- and out-of-phase. In reali-
ty, the available power lies between these extremes.
UVLO
The MAX13330/MAX13331 feature a UVLO function that
prevents the device from operating if the supply voltage
is less than 3.6V (typ). This feature ensures proper
operation during brownout conditions and prevents
deep battery discharge. Once the supply voltage
reaches the UVLO threshold, the charge-pump is
turned on and the amplifiers are powered.
Component Selection
Gain-Setting Resistors (MAX13331 Only)
The gain of the MAX13330 is internally set at -1.5V/V.
All gain-setting resistors are integrated into the device,
reducing external component count. The internally set
gain, in combination with DirectDrive, results in a head-
phone amplifier that requires only five tiny 1µF capaci-
tors to complete the amplifier circuit: two for the
charge-pump, two for audio input coupling, and one for
power-supply bypassing (see the
Typical Application
Circuits
). The gain of the MAX13331 amplifier is set
externally as shown in the
Typical Application Circuits
,
the gain is:
Choose feedback resistor values of 10kΩ. Values other
than 10kΩincrease output offset voltage due to the
input bias current, which in turn, increases the amount
of DC current flow to the load.
Input Filtering
The input capacitor (CIN), in conjunction with the input
resistor (RIN), forms a highpass filter that removes the
DC bias from an incoming signal (see the
Typical
Application 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:
Choose CIN so f-3dB is well below the lowest frequency
of interest. For the MAX13330, use the value of RIN as
given in the
Electrical Characteristics
table. Setting
f-3dB 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.
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 100mΩfor 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.
fRC
Hz
dB IN IN
−=××
3
1
2π()
AR
RVV
VF
IN
=− (/)
OUTPUT POWER vs. SUPPLY VOLTAGE
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
4.25 5.00 5.254.754.50
50
100
150
200
250
0
4.00 5.50
fIN = 1kHz
RL = 32Ω
THD+N = 10%
INPUTS
IN PHASE
INPUTS 180°
OUT OF PHASE
Figure 4. Output Power vs. Supply Voltage
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
12 ______________________________________________________________________________________
Flying Capacitor (C1)
The value of the flying capacitor (C1) 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
resistance to an extent. See the Output Power vs.
Load Resistance graph in the
Typical Operating
Characteristics
. Above 1µF, the on-resistance of the
switches and the ESR of C1 and C2 dominate.
Holding Capacitor (C2)
The hold capacitor value and ESR directly affect the
ripple at CPVSS. Increasing the value of C2 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 graph in the
Typical Operating
Characteristics
.
Power-Supply Bypass Capacitor (C3)
The power-supply bypass capacitor (C3) lowers the
output impedance of the power supply and reduces the
impact of the MAX13330/MAX13331 charge-pump
switching transients. Bypass CPVDD with C3, the same
value as C1, and place it physically close to the CPVDD
and PGND pins.
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Connect CPVDD and VDD together at the
device. Connect CPVSS and VSS together at the
device. Bypassing of both supplies is accomplished by
charge-pump capacitors C2 and C3 (see the
Typical
Application Circuits
). Place capacitors C2 and C3 as
close to the device as possible and bypass them to the
PGND plane. Keep PGND and all traces that carry
switching transients as short as possible to minimize
EMI. Route them away from SGND, the audio signal
path, and the external feedback components
(MAX13331). Connect the PGND plane and the SGND
plane together at a single point on the PCB. Refer to
the MAX13330/MAX13331 Evaluation Kit for layout
guidelines.
ESD Protection
To pass module level ESD requirements, it may be nec-
essary to add ESD diodes to the MAX13330/MAX13331
outputs. Connect the anode to the CPVSS supply, and
connect the cathode to an output pin, as shown in the
Typical Application Circuits
.
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
______________________________________________________________________________________ 13
CPVSSVSS
C1P
DIAG
OUTR
C2
1μF
C1
1μF
C1N
CLICK-AND-POP
SUPPRESSION
VDD
VSS
45kΩ
45kΩ
30kΩ
0.33μF
OUTPUT PROTECTION AND DIAGNOSTICS
UVLO/
SHUTDOWN
CONTROL
CHARGE
PUMP
OUTL
CPVDD VDD
INR
SHDN INL
PGND SGND
RIGHT CHANNEL
AUDIO IN
LEFT CHANNEL
AUDIO IN
4V to 5.5V
C3
1μF
10nF
1nF
CPVSS
ESD PROTECTION
DIODES
1nF
MAX13330
VDD
VSS
30kΩ
0.33μF
Typical Application Circuits
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
14 ______________________________________________________________________________________
Typical Application Circuits (continued)
CPVSSVSS
C1P
DIAG
OUTR
C2
1μF
C1
1μF
C1N
CLICK-AND-POP
SUPPRESSION
VDD
VSS
RF
45kΩ
OUTPUT PROTECTION AND DIAGNOSTICS
UVLO/
SHUTDOWN
CONTROL
CHARGE
PUMP
OUTL
CPVDD VDD
INR
SHDN INL
PGND SGND
RIGHT CHANNEL
AUDIO IN
LEFT CHANNEL
AUDIO IN
4V to 5.5V
C3
1μF
10nF
1nF
1nF
MAX13331
VDD
VSS
CIN
0.33μF
CIN
0.33
μ
F
RF
45kΩ
RIN
30kΩ
RIN
30kΩ
CPVSS
ESD PROTECTION
DIODES
Package Information
For the latest package outline information and land patterns (footprints), 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 PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
16 QSOP E16+4 21-0055 90-0167
MAX13330/MAX13331
Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
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 ____________________
15
© 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/08 Initial release —
1 4/09 Corrected the Features section for THD+N, style edits 1, 2, 3, 15
2 5/11
Updated the continuous power dissipation numbers in the Absolute Maximum Ratings
section; added the Package Thermal Characteristics section; added the ESD
Protection section; updated the Typical Application Circuits to add the ESD protection
diodes
2, 12, 13, 14
1 7/11
Corrected the units for the click-and-pop level parameter from V to dB in the Electrical
Characteristics table 3
