MAX98500EWE+T Maxim Integrated Products, MAX98500EWE+T Datasheet - Page 10

• 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

Figure 2. The Relationship of R
Boosted 2.2W Class D Amplifier
with Automatic Level Control
The MAX98500 is a high-efficiency Class D audio ampli-
fier that features an integrated boost converter to deliver a
constant output power over a large range of battery supply
voltages. The boost converter operates at 2MHz, requiring
only a small (2.2FH) external inductor and output capaci-
tor. The amplifier has differential inputs and an internal fully
differential design with three gain settings (6dB, 15.5dB,
and 20dB) that are selectable with a logic input.
The MAX98500 also features automatic level control. The
automatic level control reduces the output swing when
the battery voltage decreases to prevent the collapse of
battery voltage.
Figure 1. Typical Tracking Function
10
_____________________________________________________________________________________
4.0
3.9
3.8
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3.0
2.9
6
5
4
3
2
1
0
10
0
PEAK AMPLIFIER OUTPUT VOLTAGE
20
1
SLOPE
Detailed Description
vs. BATTERY VOLTAGE
BATTERY VOLTAGE (V)
V
30
KNEE
2
KNEE
R
KNEE
vs. R
40
3
(kI)
and V
KNEE
KNEE VOLTAGE
50
4
KNEE
60
5
70
6
The MAX98500 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 I
current overhead.
Traditional Class D amplifiers require the use of external
LC filters, or shielding, to meet EN55022B electromag-
netic-interference (EMI) regulation standards. Maxim’s
active emissions limiting edge-rate control circuitry
reduces EMI emissions, while maintaining up to 92%
efficiency (speaker only). Above 10MHz, the wideband
spectrum looks like noise for EMI purposes.
The MAX98500 features an automatic level control circuit
that limits the maximum speaker output swing. This helps:
U Avoid clipping
U Save the battery from collapsing, which could cause
The limiter keeps the peak voltage below a value that is a
function of battery voltage, as shown in Figure 1.
The full output swing of 5.2V is maintained for battery
voltages down to the knee voltage, while for lower battery
voltages the maximum V
The knee voltage can be changed by applying different
resistors between RKNEE and AGND. The typical track-
ing function is shifted horizontally with different R
resistor values (Figure 2).
The preamplifier gain reduces as the automatic level
control activates. The maximum gain reduction is 8dB
with a resolution of 0.5dB steps.
The attack (gain reduction) happens immediately (20Fs/
dB), while the release is set to 1.6s/dB.
The MAX98500 features three internal gain settings that
are selectable with the GAIN input. Table 1 shows the
gain settings.
Table 1. Gain Settings
a reset of the system
2
R loss of the MOSFET on-resistance and quiescent
Unconnected
AGND
GAIN
V
BAT
Low-EMI Filterless Output Stage
Class D Speaker Amplifier
PEAK
Automatic Level Control
-swing is reduced by 3V/V.
AMPLIFIER GAIN (dB)
15.5
GAIN Select
20
6
KNEE