LM49101TM/NOPB National Semiconductor, LM49101TM/NOPB Datasheet - Page 24

• Manufacturer Part Number: LM49101TM/NOPB
• Description: IC AUDIO SUBSYSTM 1.3W AB 25USMD
• Manufacturer: National Semiconductor
• Series: Boomer®, PowerWise®r
• Type: Class ABr

Specifications of LM49101TM/NOPB

• Output Type: 1-Channel (Mono) with Stereo Headphones
• Max Output Power X Channels @ Load: 1.3W x 1 @ 8 Ohm; 45mW x 2 @ 32 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: Depop, Differential Inputs, I²C, Shutdown, Thermal Protection, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 25-MicroSMD
• Operational Class: Class-AB
• Audio Amplifier Output Configuration: 1-Channel Mono/2-Channel Stereo
• Audio Amplifier Function: Headphone/Speaker
• Single Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (typ): 3/5V
• Power Supply Requirement: Triple
• Rail/rail I/o Type: No
• Power Supply Rejection Ratio: 90dB
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Dual Supply Voltage (min): 1.7/1.8/2.7V
• Dual Supply Voltage (max): 2.9/5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 25
• Package Type: uSMD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM49101TMTR

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Capacitors with a tolerance of 10% or better are recommend-
ed for impedance matching and improved CMRR and PSRR.
CHARGE PUMP FLYING CAPACITOR (C
The flying capacitor (C
lation and output impedance of the charge pump. A C
that is too low results in a loss of current drive, leading to a
loss of amplifier headroom. A higher valued C
regulation and lowers charge pump output impedance to an
extent. Above 2.2μF, the R
and the ESR of C
A lower value capacitor can be used in systems with low max-
imum output power requirements.
CHARGE PUMP HOLD CAPACITOR (C
The value and ESR of the hold capacitor C
the ripple on V
put ripple. Decreasing the ESR of C
ripple and charge pump output impedance. A lower value ca-
pacitor can be used in systems with low maximum output
power requirements.
SELECTION OF INPUT RESISTORS
The Bypass_In inputs connect to the loudspeaker output
through an FET switch when EP Bypass is active (see Figure
5). Because THD through this path is mainly dominated by
the switch impedance variation, adding input resistors (R
R
improved THD. For example, a change in the switch
impedance from 2Ω to 3Ω is a 67% change in impedance. If
10Ω input resistors are used then the impedance change is
from 12Ω to 13Ω, only 7.7% impedance variation. The analog
switch impedance is typically 2Ω to 3.4Ω. The switch
impedance change is a result of heating and the increase in
R
The value of the input resistors must be balanced against the
amount of output current and the load impedance on the loud-
speaker outputs. A higher value input resistor reduces the
effects of switch impedance variation but also causes voltage
4
DS(ON)
in Figure 5) will help reduce impedance effects resulting in
of the FETs.
SS
CP. Increasing the value of C
1
and C
1
), see Figure 1, affects the load regu-
s3
DS(ON)
dominate the output impedance.
of the charge pump switches
s3
reduces both output
S3
1
)
s3
)
1
s3
directly affects
improves load
reduces out-
1
value
3
and
24
drop and reduced power to the load on the loudspeaker out-
puts.
The current through the FET switch should not exceed 500mA
or die heating may cause thermal shut down activation and
potential IC damage.
MINIMUM POWER OPERATION
The LM49101 has several options to reduce power consump-
tion and is designed to conserve power when possible. When
a speaker only mode is selected the headphone sections are
shutdown and the current drawn from the V
power supply will be zero. When a headphone mode is se-
lected the current drawn from the V
duced by shutting down unused circuitry. See the various
Supply Current vs Supply Voltage graphs in the Typical Per-
formance Characteristics section.
To reduce power consumption further, the additional control
bits GAMP_SD, LS (EP Mode), and HPR_SD are provided.
When low power consumption is more important than the
THD performance of the loudspeaker the LS (EP_mode) bit
should be set to '1' saving approximately 0.5mA from the
V
approximately 0.4mA for each input shut down. For modes
where only the mono input is used, up to 0.8mA can be saved
from the V
shut down the right headphone channel reducing power con-
sumption when only one amplifier headphone output is need-
ed.
Additionally, the supply voltages for the different V
(V
needed values to obtain the output power levels required by
the design. By reducing the supply voltage the total power
consumption will be reduced.
For best system efficiency, a DC-DC converter (buck) can be
used to power the V
V
achieve much higher efficiency (> 90%) than even a low
dropout regulator (LDO).
DD
DD
DD
LS supply. The GAMP_SD bit should be set on to save
LS supply instead of a linear regulator. DC-DC converters
LS, V
DD
DD
LS supply. Also, the HPR_SD bit can be used to
HP, and V
DD
DD
HP and V
CP) can be set to the minimum
DD
DD
CP voltages from the
LS supply is also re-
DD
HP/V
DD
DD
pins
CP