The MAX98304 mono 3.2W Class D amplifier provides
Class AB audio performance with Class D efficiency.
This device offers five selectable gain settings (0dB,
3dB, 6dB, 9dB, and 12dB) set by a single gain-select
input (GAIN).
Active emissions-limiting, edge-rate, and overshoot control circuitry greatly reduces EMI. A filterless spreadspectrum modulation scheme eliminates the need for
output filtering found in traditional Class D devices. These
features reduce application component count.
The IC's 0.95mA at 3.7V (1.2mA at 5V) quiescent current
extends battery life in portable applications.
The IC is available in a 9-bump (1.0mm x 1.0mm) WLP
with 0.3mm pitch that is specified over the extended
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.
Page 2
Mono 3.2W Class D Amplifier
ABSOLUTE MAXIMUM RATINGS
PVDD, IN+, IN-, SHDN, GAIN to PGND ..................-0.3V to +6V
All Other Pins to PGND .........................-0.3V to (V
Continuous Current Into/Out of PVDD, PGND, OUT_ ... Q750mA
Continuous Input Current (all other pins) ........................ Q20mA
Duration of Short Circuit Between
OUT_ and PVDD, PGND .......................................Continuous
OUT+ and OUT- ....................................................Continuous
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
MAX98304
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.
PVDD
+ 0.3V)
ELECTRICAL CHARACTERISTICS
(V
bandwidth 20Hz to 22kHz, TA = T
= V
PVDD
Supply Voltage RangePVDDInferred from PSRR test2.55.5V
Undervoltage LockoutUVLOPVDD falling1.51.82.2V
Note 1: This device is 100% production tested at +25NC. All temperature limits are guaranteed by design.
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL = 4I,
Note 3: Amplifier inputs AC-coupled to ground.
Note 4: Mode transitions controlled by SHDN.
PVDD
= V
SHDN
= 5.0V, V
= 0V, AV = 12dB (GAIN = PGND), RL = J, RL connected between OUT+ to OUT-, AC measurement
PGND
MIN
to T
, unless otherwise noted. Typical values are at TA = +25NC.) (Notes 1, 2)
= 0V, AV = 6dB, RL = J, RL connected between OUT+ to OUT-, AC measurement bandwidth 20Hz
PGND
MAX98304
20
WIDEBAND vs. FREQUENCY
0
-20
-40
-60
OUTPUT MAGNITUDE (dBV)
-80
-100
FREQUENCY (MHz)
RBW = 100Hz
1010.1100
MAX98304 toc26
0
-20
-40
-60
-80
-100
OUTPUT MAGNITUDE (dBV)
-120
-140
IN-BAND vs. FREQUENCY
f = 1kHz
V
= -60dBV
OUT
10100k
FREQUENCY (Hz)
10k1k100
MAX98304 toc27
Bump Configuration
TOP VIEW
BUMP SIDE DOWN
A
B
+
MAX98304
123
OUT-
PGND
N.C.
PVDDOUT+
GAIN
C
SHDN
(1mm x 1mm x 0.64mm
IN-IN+
WLP
0.3mm PITCH)
Bump Description
BUMPNAMEFUNCTION
A1OUT-Negative Speaker Output
A2OUT+Positive Speaker Output
A3PVDD
B1PGNDGround
B2N.C.No Connection. Can be left unconnected, or connected to PGND.
B3GAINGain Select. See Table 1 for GAIN settings.
C1
SHDNActive-Low Shutdown Input. Drive SHDN low to place the device in shutdown.
Power Supply. Bypass PVDD to PGND with 0.1FF || 10FF.
Page 8
Mono 3.2W Class D Amplifier
Detailed Description
The MAX98304 features low quiescent current, a lowpower shutdown mode, comprehensive click-and-pop
suppression, and excellent RF immunity.
The device offers Class AB audio performance with
Class D efficiency in a minimal board-space solution.
The Class D amplifier features spread-spectrum modulation, edge-rate, and overshoot control circuitry that offers
MAX98304
significant improvements to switch-mode amplifier radiated emissions.
The amplifier features click-and-pop suppression that
reduces audible transients on startup and shutdown.
The amplifier includes thermal overload and short-circuit
protection.
Class D Speaker Amplifier
The filterless Class D amplifier offers much higher efficiency than Class AB amplifiers. The high efficiency of
a Class D amplifier is due to the switching operation of
the output stage transistors. Any power loss associated
with the Class D output stage is mostly due to the I2R
loss of the MOSFET on-resistance and quiescent current
overhead.
Ultra-Low EMI Filterless Output Stage
Traditional Class D amplifiers require the use of external
LC filters, or shielding, to meet EN55022B electromagnetic-interference (EMI) regulation standards. Maxim’s
patented active emissions-limiting edge-rate control
circuitry and spread-spectrum modulation reduces EMI
emissions, while maintaining up to 93% efficiency.
Maxim’s patented spread-spectrum modulation mode
flattens wideband spectral components, while proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio
reproduction or efficiency. The IC’s spread-spectrum
modulator randomly varies the switching frequency by
Q12.5kHz around the center frequency (300kHz). Above
10MHz, the wideband spectrum looks like noise for EMI
purposes (Figure 1).
Speaker Current Limit
If the output current of the speaker amplifier exceeds the
current limit (2.8A typ), the IC disables the outputs for
approximately 100Fs. At the end of 100Fs, the outputs
are reenabled. If the fault condition still exists, the IC
continues to disable and reenable the outputs until the
fault condition is removed.
Selectable Gain
The IC offers five programmable gain selections through
a single gain input (GAIN).
Table 1. Gain Control Configuration
GAIN PINMAXIMUM GAIN (dB)
Connect to PGND12
Connect to PGND through
100kW±5% resistor
Connect to PVDD6
Connect to PVDD through
100kW±5% resistor
Unconnected0
9
3
90
70
50
EN55022B LIMIT
30
EMISSIONS LEVEL (dBµV/m)
10
-10
Figure 1. EMI with 60cm of Speaker Cable and No Output Filtering
The IC features a low-power shutdown mode, drawing
less than 0.1FA (typ) of supply current. Drive SHDN low
to put the IC into shutdown.
Click-and-Pop Suppression
The IC speaker amplifier features Maxim’s comprehensive click-and-pop suppression. During startup, the
click-and-pop suppression circuitry reduces any audible
transient sources internal to the device. When entering
shutdown, the differential speaker outputs ramp down to
PGND quickly and simultaneously.
Applications Information
Filterless Class D Operation
Traditional Class D amplifiers require an output filter.
The filter adds cost, size, and decreases efficiency
and THD+N performance. The IC’s filterless modulation
scheme does not require an output filter.
Because the switching frequency of the IC is well
beyond the bandwidth of most speakers, voice coil
movement due to the switching frequency is very small.
Use a speaker with a series inductance > 10FH. Typical
8I speakers exhibit series inductances in the 20FH to
100FH range.
Component Selection
Power-Supply Input (PVDD)
PVDD powers the speaker amplifier. PVDD ranges
from 2.5V to 5.5V. Bypass PVDD with a 0.1FF and 10FF
capacitor to PGND. Apply additional bulk capacitance
at the device if long input traces between PVDD and the
power source are used.
Input Filtering
The input-coupling capacitor (CIN), in conjunction with the
amplifier’s internal input resistance (RIN), forms a highpass filter that removes the DC bias from the incoming
signal. These capacitors allow the amplifier to bias the
signal to an optimum DC level.
Assuming zero source impedance CIN is:
Layout and Grounding
MAX98304
Proper layout and grounding are essential for optimum
performance. Good grounding improves audio performance and prevents switching noise from coupling into
the audio signal.
Use wide, low-resistance output traces. As the load
impedance decreases, the current drawn from the
device increases. At higher current, the resistance of the
output traces decreases the power delivered to the load.
For example, if 2W is delivered from the device output
to a 4I load through 100mI of total speaker trace,
1.904W is being delivered to the speaker. If power is
delivered through 10mI of total speaker trace, 1.99W
is being delivered to the speaker. Wide output, supply,
and ground traces also improve the power dissipation of
the device.
The IC is inherently designed for excellent RF immunity.
For best performance, add ground fills around all signal
traces on top or bottom PCB planes.
WLP Applications Information
For the latest application details on WLP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability
testing results, refer to Application Note 1891: Wafer-level packaging (WLP) and its applications. Figure 2
shows the dimensions of the WLP balls used on the IC.
0.18mm
2R
π ×
C[ F]
=F
IN
where f
input resistance shown in the Electrical Characteristics
table. Use capacitors with adequately low voltage-coefficient for best low-frequency THD performance.
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.
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.
12 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600