TPA3113D2_15 Datasheet, PDF (24/34 Pages) Texas Instruments – 6-W FILTER-FREE STEREO CLASS-D AUDIO POWER AMPLIFIER WITH SPEAKERGUARD

TPA3113D2
SLOS650E – AUGUST 2009 – REVISED JULY 2012
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Power Supply Decoupling, C_S
The TPA3113D2 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling
to ensure that the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also
prevents oscillations for long lead lengths between the amplifier and the speaker. Optimum decoupling is
achieved by using a network of capacitors of different types that target specific types of noise on the power
supply leads. For higher frequency transients due to parasitic circuit elements such as bond wire and copper
trace inductances as well as lead frame capacitance, a good quality low equivalent-series-resistance (ESR)
ceramic capacitor of value between 220 pF and 1000 pF works well. This capacitor should be placed as close to
the device PVCC pins and system ground (either PGND pins or PowerPad) as possible. For mid-frequency noise
due to filter resonances or PWM switching transients as well as digital hash on the line, another good quality
capacitor typically 0.1 μF to 1 µF placed as close as possible to the device PVCC leads works best For filtering
lower frequency noise signals, a larger aluminum electrolytic capacitor of 220 μF or greater placed near the
audio power amplifier is recommended. The 220 μF capacitor also serves as a local storage capacitor for
supplying current during large signal transients on the amplifier outputs. The PVCC terminals provide the power
to the output transistors, so a 220 µF or larger capacitor should be placed on each PVCC terminal. A 10 µF
capacitor on the AVCC terminal is adequate. Also, a small decoupling resistor between AVCC and PVCC can be
used to keep high frequency class D noise from entering the linear input amplifiers.
BSN and BSP Capacitors
The full H-bridge output stages use only NMOS transistors. Therefore, they require bootstrap capacitors for the
high side of each output to turn on correctly. A 0.22 μF ceramic capacitor, rated for at least 25 V, must be
connected from each output to its corresponding bootstrap input. Specifically, one 0.22 μF capacitor must be
connected from OUTPx to BSPx, and one 0.22 μF capacitor must be connected from OUTNx to BSNx. (See the
application circuit diagram in Figure 1.)
The bootstrap capacitors connected between the BSxx pins and corresponding output function as a floating
power supply for the high-side N-channel power MOSFET gate drive circuitry. During each high-side switching
cycle, the bootstrap capacitors hold the gate-to-source voltage high enough to keep the high-side MOSFETs
turned on.
Differential Inputs
The differential input stage of the amplifier cancels any noise that appears on both input lines of the channel. To
use the TPA3113D2 with a differential source, connect the positive lead of the audio source to the INP input and
the negative lead from the audio source to the INN input. To use the TPA3113D2 with a single-ended source, ac
ground the INP or INN input through a capacitor equal in value to the input capacitor on INN or INP and apply
the audio source to either input. In a single-ended input application, the unused input should be ac grounded at
the audio source instead of at the device input for best noise performance. For good transient performance, the
impedance seen at each of the two differential inputs should be the same.
The impedance seen at the inputs should be limited to an RC time constant of 1 ms or less if possible. This is to
allow the input dc blocking capacitors to become completely charged during the 14 ms power-up time. If the input
capacitors are not allowed to completely charge, there will be some additional sensitivity to component matching
which can result in pop if the input components are not well matched.
Using LOW-ESR Capacitors
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal) capacitor
can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this resistor
minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this resistance,
the more the real capacitor behaves like an ideal capacitor.
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