MAX98500EWE+T Maxim Integrated Products, MAX98500EWE+T Datasheet - Page 11

• Manufacturer Part Number: MAX98500EWE+T
• Description: IC AMP BOOST CLASS D 2.2W 16WLP
• Manufacturer: Maxim Integrated Products
• Type: Class Dr

Specifications of MAX98500EWE+T

• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 2.2W x 1 @ 8 Ohm
• Voltage - Supply: 2.5 V ~ 5.5 V
• Features: Depop, Differential Inputs, Short-Circuit and Thermal Protection, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 16-WLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 2. Shutdown Configurations
The MAX98500 features two active-low shutdown inputs
(SDSPK and SDBST). Table 2 shows the different shut-
down configurations.
The MAX98500 speaker amplifier features Maxim’s com-
prehensive 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 SPKPGND quickly and simultaneously.
The IC features overcurrent and thermal protection.
The IC shuts down when the V
to about 80% of the expected output. The IC also
enters into shutdown when the die temperature exceeds
+165NC. The device remains in shutdown until power
is reset or SDBST is toggled low and back high after
the fault condition has been removed. The IC speaker
amplifier also features a 2A (typ) short-circuit protection
scheme.
The MAX98500 features a two-stage, soft-start, power-
up sequence. When SDBST is taken high and V
above UVLO the soft-start first ramps V
to V
Once the V
switching turns on and ramps the V
(typ), see the Soft-Start graph in the Typical Operating
Characteristics. The maximum load current is available
after the soft-start is completed.
The undervoltage lockout (UVLO) circuit compares the
voltage at V
ensure that the input voltage is high enough for reliable
operation. Once the V
SDBST
BAT
High
High
Low
Low
Current-Limit and Thermal Protection
voltage with a battery current of 300mA (typ).
CCOUT
BAT
with the UVLO threshold (2.2V typ) to
______________________________________________________________________________________
SDSPK
reaches the V
High
High
Low
Low
Click-and-Pop Suppression
BAT
Undervoltage Lockout (UVLO)
voltage exceeds the UVLO
CCOUT
STATUS
BOOST
BAT
Off
Off
On
On
CCOUT
Boost Converter
voltage, the internal
output decreases
Boosted 2.2W Class D Amplifier
CCOUT
to 5.5V in 5ms
Shutdown
SPEAKER
with Automatic Level Control
STATUS
Soft-Start
Off
Off
Off
On
quickly
BAT
is
threshold, the soft-start begins. When the input voltage
falls below the UVLO threshold, the boost converter and
speaker amplifier turn off.
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filter adds cost, increases the solution size of the ampli-
fier, and can decrease efficiency and THD+N perfor-
mance. The traditional PWM scheme uses large differen-
tial output swings (2 x supply voltage peak-to-peak) and
causes large ripple currents. Any parasitic resistance in
the filter components results in a loss of power and low-
ers the efficiency.
The MAX98500 does not require an output filter. The
device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and
the human ear to recover the audio component of the
square-wave output. Eliminating the output filter results
in a smaller, less costly, and more efficient solution.
Because the frequency of the MAX98500 output is well
beyond the bandwidth of most speakers, voice coil
movement due to the square-wave frequency is very
small. Although this movement is small, a speaker not
designed to handle the additional power can be dam-
aged. For optimum results, use a speaker with a series
inductance > 10FH. Typical 8I speakers exhibit series
inductances in the 20FH to 100FH range.
GSM radios transmit using time-division multiple access
(TDMA) with 217Hz intervals. The result is an RF signal
with strong amplitude modulation at 217Hz and its har-
monics that is easily demodulated by audio amplifiers.
The MAX98500 is designed specifically to reject RF
signals; however, PCB layout has a large impact on the
susceptibility of the end product.
In RF applications, improvements to both layout and
component selection decrease the MAX98500’s suscep-
tibility to RF noise and prevent RF signals from being
demodulated into audible noise. Trace lengths should be
kept below 1/4 of the wavelength of the RF frequency of
interest. Minimizing the trace lengths prevents them from
functioning as antennas and coupling RF signals into the
MAX98500. The wavelength (l) in meters is given by:
l = c/f where c = 3 x 10
of interest.
Applications Information
Filterless Class D Operation
8
m/s, and f = the RF frequency
RF Susceptibility
11