Maxim MAX97200AEWC Low-power, low-offset, dual mode, class h directdrive headphone amplifier Datasheet

19-4981; Rev 2; 3/11
TION KIT
EVALUA BLE
AVAILA
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
The MAX97200 is a 45mW Class H headphone amplifier
that runs from a single low 1.8V supply voltage and employs
Maxim’s second-generation DirectDrive technology.
The MAX97200 features a Dual ModeK internal charge
pump to generate the power rails for the amplifier. The
charge-pump output can be QPVIN/2 or QPVIN depending on the amplitude of the output signal. When the output voltage is low, the power-supply voltage is QPVIN/2.
When the output signal demands larger output voltage,
the charge pump switches modes so that a greater
power-supply voltage is realized and more output power
can be delivered to the load.
Second-generation DirectDrive technology improves
power consumption when compared to first-generation
DirectDrive amplifiers. The MAX97200 can be powered
from a regulated 1.8V and have similar power consumption to a traditional DirectDrive amplifier that is powered
from 0.9V.
Maxim’s DirectDrive architecture uses an inverting
charge pump to derive a negative voltage supply. The
headphone amplifier is powered between the positive
supply and the generated negative rail. This scheme
allows the audio output signal to be biased about
ground, eliminating the need for large DC-blocking
capacitors between the amplifier output and the headphone load.
Features
S Second-Generation DirectDrive Technology
S Dynamic, Class H, Dual Mode Charge Pump
S Low Voltage Operation, VPVIN = 1.8V
S Low Quiescent Current, 1.15mA (typ) at VPVIN =
1.8V
S Eliminates Large Output DC-Blocking Capacitors
S Industry-Leading Click-and-Pop Performance
S High-Fidelity, SNR 105dB (5.6µV Output Noise)
S Output Power 34mW into 32I (THD+N 1%)
S Output Power 45mW into 16I (THD+N 10%)
S Tiny, 12-Bump, 1.27mm x 1.65mm (0.4mm Lead
Pitch) WLP Package
Ordering Information/
Selector Guide
PART
GAIN
(dB)
MAX97200AEWC+
3
12 WLP
ABF
MAX97200BEWC+
0
12 WLP
ABG
+Denotes a lead(Pb)-free and RoHS-compliant package.
Typical Operating Circuit
The MAX97200 is available in a tiny, 12-bump wafer
level packaging (WLP 1.27mm x 1.65mm) with a small,
0.4mm lead pitch and specified over the -40NC to +85NC
extended temperature range.
MAX97200
LEFT AUDIO
INPUT
Applications
Smartphones
APPLICATIONS
PROCESSOR
LEFT AUDIO OUTPUT
SHDN
RIGHT AUDIO
INPUT
RIGHT AUDIO
OUTPUT
MP3 Players
VoIP Phones
TOP
MARK
Note: All devices operate over the -40°C to +85°C temperature range.
Low-output offset voltage provides very good click-andpop performance both into and out of shutdown. High
signal-to-noise ratio maintains system fidelity.
Cellular Phones
PINPACKAGE
CHARGE
PUMP
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.
MAX97200
General Description
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
ABSOLUTE MAXIMUM RATINGS
PVIN or PVDD to PGND........................................-0.3V to +2.2V
GND to PGND.......................................................-0.3V to +0.3V
PVSS to PGND......................................................-2.2V to +0.3V
OUT_ and IN_ to GND.............. (PVSS - 0.2V) to (PVDD + 0.2V)
C1P, C1N....................................................Cap connection only
SHDN to GND..........................................................-0.3V to +4V
Output Short-Circuit Current......................................Continuous
Thermal Limits (Note 1)
Multiple Layer PCB
Continuous Power Dissipation (TA = +70NC)
12-Bump WLP (derate 13.7mW/NC above +70NC).....1095mW
Junction Temperature..................................................+150NC
Operating Temperature Range........................... -40NC to +85NC
Storage Temperature Range............................. -65NC to +150NC
Soldering Temperature (reflow).......................................+260NC
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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
Junction-to-Ambient Thermal Resistance (BJA)...............73NC/W
Junction-to-Case Thermal Resistance (BCA)...................30NC/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25NC.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
1.62
1.80
1.98
V
1.48
1.58
V
POWER SUPPLY
Supply Voltage Range
PVIN
Guaranteed by PSRR
UVLO Rising
UVLO Falling
1.36
1.46
V
Inputs grounded, TA = +25NC, no load
1.15
16I load, inputs grounded, TA = +25NC
1.16
ISHDN
tON
VSHDN = 0V, TA = +25NC
0.2
Oscillator Frequency
fOSC1
VOUT = 0V, TA = +25NC
Oscillator Frequency
fOSC2
VOUT = 0.2V, RL = J, fIN = 1kHz
665
kHz
Oscillator Frequency
fOSC3
VOUT = 0.5V, RL = J, fIN = 1kHz
500
kHz
Positive Output Voltage
VPVDD
Quiescent Supply Current
Shutdown Current
Turn-On Time
IDD
1.7
mA
FA
0.6
1
ms
83
88
kHz
CHARGE PUMP
Negative Output Voltage
Output Voltage Threshold
VPVSS
VTH1
78
VOUT = 0.2V, RL = J
PVIN/2
VOUT = 0.5V, RL = J
PVIN
VOUT = 0.2V, RL = J
-PVIN/2
VOUT = 0.5V, RL = J
-PVIN
RL = J, output voltage at which the
charge pump switches modes, VOUT
rising, transition from 1/8 to normal
frequency
QPVIN
x
0.08
2 _______________________________________________________________________________________
V
V
V
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25NC) (Note 2)
PARAMETER
Output Voltage Threshold
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
VTH2
RL = J, output voltage at which the
charge pump switches modes, VOUT
rising, transition from high-efficiency
mode to high-power mode
QPVIN
x
0.24
V
tHOLD
Time it takes for the charge pump to
transition from high-power mode to
high-efficiency mode; RL = J
32
ms
tRISE
Time it takes for the charge pump to
transition from high-efficiency mode to highpower mode (90% of its value); RL = J
20
Fs
Charge-Pump Mode Transition
Timeouts (Figure 2)
AMPLIFIER
Voltage Gain
AV
Maximum Output Voltage
MAX97200A
2.75
2.92
3.09
MAX97200B
-0.17
0
+0.17
RL = 10kI, THD+N = 1%
1.295
RL = 10kI, THD+N = 10%
1.44
Channel-to-Channel Gain
Matching
VOS
Input Resistance
RIN
TA = +25NC
Q0.1
Output Power
PSRR
POUT
Line Output Voltage
Total Harmonic Distortion Plus
Noise
Output Noise
VLINE
THD+N
VN
Signal-to-Noise Ratio
Click-and-Pop Level
Crosstalk
Q0.3
6
10
14
MAX97200B
7.2
12
16.8
62
83
100mVP-P ripple
THD+N = 1%
fIN = 217Hz
96
fIN = 1kHz
94
fIN = 20kHz
61
RL = 10kI
0.16
RL = 32I
34
RL = 16I
45
1
RL = 10kI
RL = 16I, POUT = 0.1mW, fIN = 1kHz (Note 3)
0.02
RL = 16I, POUT = 10mW, fIN = 1kHz (Note 4)
0.003
RL = 10kI, VOUT = 1V, fIN = 1kHz (Note 4)
0.008
mV
kI
dB
mW
VRMS
%
Inputs grounded, A-weighted, MAX97200B
5.6
FV
SNR
A-weighted, MAX97200B
105
dB
VCP
RL = 32I, peak
voltage, A-weighted,
32 samples/second,
MAX97200B
XTALK
Maximum Capacitive Load
dB
MAX97200A
VPVDD = 1.62V to 1.98V, TA = +25NC
Power-Supply Rejection Ratio
VPK
Q0.1
Total Output Offset Voltage
dB
Into shutdown
80
Out of shutdown
68
dBV
RL = 16I, 1kHz, POUT = 5mW
94
dB
200
pF
_______________________________________________________________________________________ 3
MAX97200
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at TA = +25NC) (Note 2)
PARAMETER
SYMBOL
DIGITAL INPUT (SHDN)
Input High Voltage
VIH
Input Low Voltage
VIL
CONDITIONS
MIN
TYP
MAX
UNITS
1.4
V
0.4
IIH
Input Leakage Current
IIL
VSHDN = 4V, TA = +25NC
-1
+1
VSHDN = 1.8V, TA = +25NC
-1
+1
VSHDN = 0V, TA = +25NC
-1
+1
V
FA
Note 2: All specifications are 100% tested at TA = +25NC. Temperature limits are guaranteed by design.
Note 3: VPVDD = 0.9V, VPVSS = -0.9V.
Note 4: VPVDD = 1.8V, VPVSS = -1.8V.
Typical Operating Characteristics
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, both channels driven in phase, TA = +25NC,
unless otherwise noted.)
THD+N vs. OUTPUT POWER
1
0.1
fIN = 100Hz
fIN = 100Hz
50
60
0.001
70
20
0.1
POUT = 20mW
POUT = 25mW
RL = 32I
0.1
POUT = 20mW
POUT = 2mW
0.001
1
0
0.5
10
100
1.0
1.5
2.0
2.5
THD+N vs. FREQUENCY
0.01
0.001
FREQUENCY (kHz)
60
VOUT (VRMS)
1
THD+N (%)
1
0.1
50
THD+N vs. FREQUENCY
10
MAX97200 toc04
RL = 16I
0.01
40
10
MAX97200 toc05
THD+N vs. FREQUENCY
0.01
30
POUT (mW)
POUT (mW)
10
fIN = 6kHz
0.001
10
0
80
MAX97200 toc06
40
0.01
RL = 10kI
1
THD+N (%)
30
fIN = 100Hz
fIN = 6kHz
fIN = 6kHz
0.001
20
0.1
fIN = 1kHz
0.01
fIN = 1kHz
10
1
fIN = 1kHz
0.01
0
RL = 10kI
10
THD+N (%)
0.1
RL = 32I
10
THD+N (%)
1
THD+N vs. OUTPUT VOLTAGE
100
MAX97200 toc03
MAX97200 toc01
RL = 16I
10
THD+N (%)
100
MAX97200 toc02
THD+N vs. OUTPUT POWER
100
THD+N (%)
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
0.1
VOUT = 0.868VRMS
VOUT = 1.12VRMS
0.01
POUT = 2mW
0.01
0.1
POUT = 25mW
0.001
1
FREQUENCY (kHz)
10
100
VOUT = 0.316VRMS
0.01
0.1
1
FREQUENCY (kHz)
4 _______________________________________________________________________________________
10
100
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
OUTPUT POWER
vs. LOAD RESISTANCE
1% THD + N
20
C1 = C2 = C3 = .47µF
40
C1 = C2 = C3 = 2.2µF
30
10
100
1000
MAX97200 toc09
40
100
10
1000
10
1
10,000
100
POWER DISSIPATION
vs. OUTPUT POWER
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.15
SUPPLY CURRENT (mA)
70
60
RL = 32I
30
20
1.10
1.05
1.00
0.95
0.90
10
0.85
0
0.80
10
1
RL = J
100
RL = J
0.18
0.16
SUPPLY CURRENT (µA)
RL = 16I
0.20
MAX97200 toc11
MAX97200 toc10
1.20
MAX97200 toc12
OUTPUT POWER (mW)
80
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00
OUTPUT POWER (mW)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
CROSSTALK vs. FREQUENCY
5mW 16I
CROSSTALK (dB)
-40
-60
-80
-100
-120
0.1
1
FREQUENCY (kHz)
10
100
OUTPUT POWER = 5mW
RL = 16I
IN-BAND OUTPUT SPECTRUM
0
MAX97200 toc15
VRIPPLE = 200mVP-P
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
MAX97200 toc14
MAX97200 toc13
1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00
-20
0.01
60
LOAD RESISTANCE (I)
90
40
80
LOAD RESISTANCE (I)
100
50
100
0
0
10,000
120
20
f = 1kHz
-20
OUTPUT MAGNITUDE (dBV)
1
POWER DISSIPATION (mW)
50
140
10
0
0
C1 = C2 = C3 = 1µF
20
10
PSRR (dB)
60
160
POWER CONSUMPTON (mW)
40
30
70
OUTPUT POWER (mW)
10% THD + N
50
MAX97200 toc08
70
OUTPUT POWER (mW)
80
MAX97200 toc07
80
60
POWER CONSUMPTION
vs. OUTPUT POWER
OUTPUT POWER vs. LOAD RESISTANCE
AND CHARGE-PUMP CAPACITOR
-40
-60
-80
-100
-120
-140
-160
-120
20
50 100 200
500 1k 2k
FREQUENCY (Hz)
5k 10k 20k
0.01
0.1
1
10
100
FREQUENCY (Hz)
_______________________________________________________________________________________ 5
MAX97200
Typical Operating Characteristics (continued)
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, both channels driven in phase, TA = +25NC,
unless otherwise noted.)
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
Typical Operating Characteristics (continued)
(VPVIN = 1.8V, VPGND = VGND = 0V, VSHDN = 1.8V, C1 = C2 = C3 = 1FF, C4 = 10FF, both channels driven in phase, TA = +25NC,
unless otherwise noted.)
SUPPLY MODE SWITCHING
TURN-ON RESPONSE
MAX97200 toc16
MAX97200 toc17
RL = 16I
PVDD
OUTPUT
PVSS
SHDN
20ms/div
400µs/div
TURN-OFF RESPONSE
MAX97200 toc18
OUTPUT
SHDN
400µs/div
6 _______________________________________________________________________________________
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
TOP VIEW
MAX97200
1
2
3
4
A
OUTR
PVSS
C1N
C1P
B
OUTL
SHDN
GND
PGND
C
INL
INR
PVDD
PVIN
WLP
Pin Description
BUMP
NAME
A1
OUTR
Right Amplifier Output
FUNCTION
A2
PVSS
Negative Charge-Pump Output. Connect a 1FF capacitor between PVSS and PGND.
A3
C1N
Charge-Pump Flying Cap Negative Connection. Connect 1FF capacitor between C1N and C1P.
A4
C1P
Charge-Pump Flying Cap Positive Connection. Connect 1FF capacitor between C1P and C1N.
B1
OUTL
Left Amplifier Output
B2
SHDN
GND
Active-Low Shutdown
B3
B4
PGND
Power Ground. Connect to GND.
C1
INL
Left Audio Input
C2
INR
Right Audio Input
C3
PVDD
Positive Charge-Pump Output. Bypass to PGND with 1FF.
C4
PVIN
Main Power-Supply Connection. Bypass to PGND with 10FF.
Signal Ground. Connect to PGND.
_______________________________________________________________________________________ 7
MAX97200
Pin Configuration
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
Detailed Description
The MAX97200 is a 45mW Class H headphone amplifier that runs from a single low 1.8V supply voltage
and employs Maxim’s second-generation DirectDrive
technology.
Maxim’s DirectDrive architecture uses an inverting
charge pump to derive a negative voltage supply. The
headphone amplifier is powered between the positive
supply and the generated negative rail. This scheme
allows the audio output signal to be biased about
ground, eliminating the need for large DC blocking
capacitors between the amplifier output and the headphone load.
Second-generation DirectDrive technology improves
power consumption when compared to first-generation
DirectDrive amplifiers. The MAX97200 can be powered
from a regulated 1.8V supply and have similar power
consumption to a traditional DirectDrive amplifier that is
powered from 0.9V.
The MAX97200 features a dual-mode internal charge
pump to generate the power rails for the DirectDrive
amplifier. The charge-pump output can be QPVIN/2 or
QPVIN depending on the amplitude of the output signal.
When the output voltage is low the power-supply voltage is QPVIN/2. When the output signal demands larger
output voltage, the charge pump switches modes so
that a greater power-supply voltage is realized and more
output power can be delivered to the load.
DirectDrive Headphone Amplifier
Traditional single-supply headphone amplifiers have
outputs biased at a nominal DC voltage (typically half
the supply). 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 headphone, resulting in unnecessary power dissipation and possible damage to both headphone and
headphone amplifier.
Maxim’s second-generation DirectDrive architecture
uses a charge pump to create an internal negative supply voltage. This allows the headphone outputs of the
MAX97200 to be biased at GND while operating from a
single supply (Figure 1). Without a DC component, there
is no need for the large DC-blocking capacitors. Instead
of two large (220FF typ) capacitors, the MAX97200
charge pump requires 3 small ceramic capacitors, conserving board space, reducing cost, and improving the
frequency response of the headphone amplifier.
VOUT
VDD
VDD / 2
VDD
GND
CONVENTIONAL DRIVER BIASING SCHEME
VOUT
+VDD
GND
2VDD
-VDD
DirectDrive BIASING SCHEME
Figure 1. Traditional Amplifier vs. MAX97200 DirectDrive
Output
8 _______________________________________________________________________________________
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
High-power mode is similar to Maxim’s traditional
DirectDrive architecture and is best suited for loads
that require high voltage swing. High-efficiency mode
improves power consumption by reducing the powersupply voltage across the amplifier’s output stage by
half. The reduced power-supply voltage is good for idle
conditions or low-signal level conditions into a headphone.
Class H Operation
The MAX97200’s internal Class H amplifier uses a class
AB output stage with multiple, discrete power supplies.
This result’s in two power-supply differentials of 1.8V and
3.6V generated from a single 1.8V external supply. The
PVIN/2 power-supply differential is used when the output
voltage requirements are low, and the output is below
VTH2 as seen in Figure 2. The higher supply differential
is used when the output voltage exceeds the high
threshold VTH2, maximizing output power and voltage
swing. The transition time from high-efficiency mode to
high-power mode occurs when the threshold is crossed.
VPVDD
IN_
VPVSS
10ms/div
Figure 2. Inverting and Split Mode Transitions
The switch from high-power mode to high-efficiency
mode occurs 32ms (typ) after the threshold is crossed.
Built-in hysteresis keeps the charge pump from erratic
mode switching when the output voltage is near the high
and low thresholds.
Click-and-Pop Suppression
In conventional single-supply audio amplifiers, the output-coupling capacitor contributes significantly to 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 discharged. This results in a DC shift across the capacitor,
which appears as an audible transient at the speaker.
Since the MAX97200 does not require output coupling
capacitors, this problem does not arise. Additionally,
the MAX97200 features extensive click-and-pop suppression that eliminates any audible transient sources
internal to the device.
Typically, the output of the device driving the MAX97200
has a DC bias of half the supply voltage. At startup, the
input-coupling capacitor, CIN, is charged to the preamplifier’s DC bias voltage through the MAX97200 input
resistor, RIN. This DC shift across the capacitor results
in an audible click-and-pop. The MAX97200 precharges
the input capacitors when power is applied to ensure
that no audible clicks or pops are heard when SHDN is
pulled high.
Shutdown
The MAX97200 features a 1FA, low-power shutdown
mode that reduces quiescent current consumption and
extends battery life. Shutdown is controlled by the SHDN
input. Driving the SHDN input low disables the drive
amplifiers and charge pump and sets the headphone
amplifier output resistance to 100I.
Applications Information
Component Selection
Input-Coupling Capacitor
The input capacitor (CIN), in conjunction with the amplifier input resistance (RIN_), forms a highpass filter that
removes the DC bias from the incoming signal. The
AC-coupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero source impedance, the -3dB point of the highpass filter is given by:
f- 3dB =
1
2πRINCIN
_______________________________________________________________________________________ 9
MAX97200
Dual Mode Charge Pump
The MAX97200’s Dual Mode, charge pump outputs
either QPVIN/2 in high-efficiency mode or QPVIN in highpower mode, resulting in a power-supply differential of
1.8V or 3.6V. The charge-pump mode changes based
on the level of the output signal needed. When the
output voltage is small, the voltage rails are reduced to
minimize power consumption. When the output voltage
is large, the voltage rails are increased to accommodate
the larger output need.
RIN is the amplifier’s input resistance value. Choose CIN
such that f-3dB is well below the lowest frequency of
interest. Setting f-3dB too high affects the amplifier’s low
frequency. Capacitors with higher voltage coefficients,
such as ceramics, result in increased distortion at low
frequencies.
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 100mI for optimum performance. Low ESR ceramic capacitors minimize the output resistance of the charge pump. For best
performance over the extended temperature range,
select capacitors with an X7R dielectric.
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, which leads to a loss
of output voltage. Connect a 1FF capacitor between C1P
and C1N.
Output Capacitors (C2, C3)
The output capacitor value and ESR directly affect the
ripple at PVSS. Increasing the value of C2 and C3 reduces output ripple. Likewise, decreasing the ESR of C2 and
C3 reduces both ripple and output resistance. Lower
capacitance values can be used in systems with low
maximum output power levels. Connect a 1FF capacitor between PVDD and PGND. Connect a 1FF capacitor
between PVSS and PGND.
RF Susceptibility
Improvements to both layout and component selection can decrease the MAX97200 susceptibility to RF
noise and prevent RF signals from being demodulated
into audible noise. Trace lengths should be kept below
¼ of the wavelength of the RF frequency of interest.
Minimizing the trace lengths prevents the traces from
functioning as antennas and coupling RF signals into the
MAX97200. The wavelength (λ) in meters is given by:
λ = c/f
where c = 3 x
interest.
108
m/s, and f is the RF frequency of
Route audio signals to the middle layers of the PCB to
allow the ground planes above and below to shield them
from RF interference. Ideally, the top and bottom layers
of the PCB should primarily be ground planes to create
effective shielding.
Additional RF immunity can also be obtained from relying on the self-resonant frequency of capacitors as
it exhibits the frequency response similar to a notch
filter. Depending on the manufacturer, 10pF to 20pF
capacitors typically exhibit self resonance at RF frequencies. These capacitors when placed at the input pins
can effectively shunt the RF noise at the inputs of the
MAX97200. For these capacitors to be effective, provide
a low-impedance, low-inductance path from the capacitors to the ground plane. Do not use microvias to connect to the ground plane as these vias do not conduct
well at RF frequencies. Figure 3 shows headphone RF
immunity with a well laid out PCB.
HEADPHONE RF IMMUNITY
vs. FREQUENCY
0
-10
-20
OUTPUT NOISE (dBV)
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
-30
-40
-50
-60
RIGHT CHANNEL
-70
LEFT CHANNEL
-80
-90
-100
1000
1500
2000
2500
3000
FREQUENCY (MHz)
Figure 3. Headphone RF Immunity
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance, as well as route heat away
from the device. Good grounding improves audio performance, minimizes crosstalk between channels, and
prevents switching noise from coupling into the audio
signal. Connect PGND and GND together at a single
point on the PCB. Route PGND and all traces that carry
switching transients away from GND, and the traces and
components in the audio signal path.
Connect C2 to the PGND plane. Place the charge-pump
capacitors (C1, C2) as close as possible to the device.
Bypass PVDD with a 1FF capacitor to PGND. Place the
bypass capacitors as close as possible to the device.
10 �������������������������������������������������������������������������������������
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
Chip Information
PROCESS: BiCMOS
1.8V
C4
10µF
PVIN
C4
MAX97200
RFB
PVDD
INL C1
B1 OUTL
RIN
INR C2
A1 OUTR
RIN
SHDN
GND
PVSS
B2
RFB
A2 PVSS
CHARGE
PUMP
B3
B4
PGND
C3
A3
PVDD
C1N
C3
1µF
A4
C2
1µF
C1P
C1
1µF
______________________________________________________________________________________ 11
MAX97200
Simplified Functional Diagram
MAX97200
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
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.
12 WLP
W121A1+1
21-0449
Refer to Application Note 1891
12 �������������������������������������������������������������������������������������
Low-Power, Low-Offset, Dual Mode, Class H
DirectDrive Headphone Amplifier
REVISION
NUMBER
REVISION
DATE
0
1/10
Initial release
—
1
3/10
Removed shutdown current max value
2
2
3/11
Corrected crosstalk data in TOC 14
5
DESCRIPTION
PAGES
CHANGED
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
©
2011 Maxim Integrated Products
13
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX97200
Revision History
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