Datasheet

LM48100Q
www.ti.com SNAS470D –OCTOBER 2008–REVISED MARCH 2013
Table 7. Volume Control (continued)
Volume Step VOL4 VOL3 VOL2 VOL1 VOL0 Gain (dB)
32 1 1 1 1 1 18
SHUTDOWN FUNCTION
The LM48100Q features an I
2
C selectable low power shutdown mode that disables the device, reducing
quiescent current consumption to 0.01μA. Set bit B4 (POWER_ON) in the Mode Control Register to 0 to disable
the device. Set B0 to 1 to enable the device.
POWER DISSIPATION
The increase in power delivered by a BTL amplifier leads to a direct increase in internal power dissipation. The
maximum power dissipation for a BTL amplifier for a given supply voltage and load is given by Equation 2:
P
DMAX
= 4 x V
DD
2
/ 2π
2
R
L
(Watts) (2)
The maximum power dissipation of the HTSSOP package is calculated by Equation 3:
P
DMAX (PKG)
= T
JMAX
— T
A
/ θ
JA
(Watts) (3)
where T
JMAX
is 150°C, T
A
is the ambient temperature and θ
JA
is the thermal resistance specified in the Absolute
Maximum Ratings.
If the power dissipation for a given operating condition exceeds the package maximum, either decrease the
ambient temperature, increase air flow, add heat sinking to the device, or increase the load impedance and/or
supply voltage. The LM48100Q HTSSOP package features an exposed die attach pad (DAP) that can be used
to increase the maximum power dissipation of the package, see Exposed DAP Mounting Considerations.
The LM48100Q features thermal overload protection that disables the amplifier output stage when the die
temperature exceeds +170°C. See the Thermal Overload Detection section.
PROPER SELECTION OF EXTERNAL COMPONENTS
Power Supply Bypassing/Filtering
Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass
capacitors as close to the device as possible. Place a 1µF ceramic capacitor from V
DD
to GND. Additional bulk
capacitance may be added as required.
Input Capacitor Selection
Input capacitors may be required for some applications, or when the audio source is single-ended. Input
capacitors block the DC component of the audio signal, eliminating any conflict between the DC component of
the audio source and the bias voltage of the LM48100Q. The input capacitors create a high-pass filter with the
input resistors R
IN
. The -3dB point of the high-pass filter is found using Equation 4 below.
f = 1 / 2πR
IN
C
IN
(Hz) (4)
Where the value of R
IN
is given in the Electrical Characteristics Table.
High pass filtering the audio signal helps protect the speakers. When the LM48100Q is using a single-ended
source, power supply noise on the ground is seen as an input signal. Setting the high-pass filter point above the
power supply noise frequencies, filters out the noise such that it is not amplified and heard on the output.
Capacitors with a tolerance of 10% or better are recommended for impedance matching and improved PSRR.
Bias Capacitor Selection
The LM48100Q internally generates a V
DD
/2 common-mode bias voltage. The BIAS capacitor C
BIAS
, improves
PSRR and THD+N by reducing noise at the BIAS node. Use a 2.2µF ceramic placed as close to the device as
possible.
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