TPA2011D1_15 Datasheet, PDF (13/30 Pages) Texas Instruments – Mono Filter-Free Class-D Audio Power Amplifier

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9 Detailed Description
TPA2011D1
SLOS626B – DECEMBER 2009 – REVISED NOVEMBER 2015
9.1 Overview
The TPA2011D1 is a high-efficiency filter-free Class-D audio amplifier capable of delivering up to 3.2W into 4-Ω
load with 5-V power supply. The fully-differential design of this amplifier avoids the usage of bypass capacitors
and the improved CMRR eliminates the usage of input-coupling capacitors. This makes the device size a perfect
choice for small, portable applications as only three external components are required. The advanced modulation
used in the TPA2011D1 PWM output stage eliminates the need for an output filter.
9.2 Functional Block Diagram
Input
EN
Buffer
SC
300 KΩ
9.3 Feature Description
9.3.1 Fully Differential Amplifier
The TPA2011D1 is a fully differential amplifier with differential inputs and outputs. The fully differential amplifier
consists of a differential amplifier and a common-mode amplifier. The differential amplifier ensures that the
amplifier outputs a differential voltage on the output that is equal to the differential input times the gain. The
common-mode feedback ensures that the common-mode voltage at the output is biased around VDD/2
regardless of the common-mode voltage at the input. The fully differential TPA2011D1 can still be used with a
single-ended input; however, the TPA2011D1 should be used with differential inputs when in a noisy
environment, like a wireless handset, to ensure maximum noise rejection.
9.3.1.1 Advantages of Fully Differential Amplifiers
• Input-coupling Capacitors Not Required
– The fully differential amplifier allows the inputs to be biased at voltage other than mid-supply. For example,
if a codec has a midsupply lower than the midsupply of the TPA2011D1, the common-mode feedback
circuit will adjust, and the TPA2011D1 outputs will still be biased at midsupply of the TPA2011D1. The
inputs of the TPA2011D1 can be biased from 0.5 V to VDD –0.8 V. If the inputs are biased outside of that
range, input-coupling capacitors are required.
• Midsupply Bypass Capacitor, C(BYPASS), Not Required
– The fully differential amplifier does not require a bypass capacitor. This is because any shift in the
midsupply affects both positive and negative channels equally and cancels at the differential output.
• Better RF-Immunity
– GSM handsets save power by turning on and shutting off the RF transmitter at a rate of 217 Hz. The
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