1 Features
1• Stereo DirectPath™ Headphone Amplifier
– 40 mW Into 32 Ω With 3.3-V Supply
• Low THD+N < 0.01% at 10 mW Into 32 Ω
• High SNR, >90 dB
• Differential Input and Single-Ended Output
• Adjustable Gain by External Gain-Setting
Resistors
• Configurable as a Second-Order Low-Pass Filter
– Ideal for PWM Audio Sources
• Low DC Offset, <1 mV
• Ground-Referenced Outputs Eliminate DC-
Blocking Capacitors
– Reduce Board Area
– Reduce Component Cost
– Improve THD+N Performance
– No Degradation of Low-Frequency Response
Due to Output Capacitors pop•
Short-Circuit Protection
• Click- and Pop-Reduction Circuitry
• External Undervoltage Mute
• Active Mute Control for Pop-Free Audio On/Off
Control
• Space-Saving TSSOP Package

2 Applications
• LCD and PDP TV
• Blu-ray Disc™, DVD Players
• Set-Top Boxes
• Mini/Micro Combo Systems
• Sound Cards
• Laptops

3 Description
The TPA6138A2 is a pop-free stereo headphone
amplifier designed to allow the removal of the output dc-blocking capacitors for reduced component count
and cost. The device is ideal for single-supply
electronics where size and cost are critical design
parameters.
Designed using TI’s patented DirectPath™
technology, The TPA6138A2 is capable of driving 25
mW into a 32-Ω load with 3.3-V supply voltage. The device has differential inputs and uses external gain-
setting resistors that supports a gain range of ±1 V/V
to ±10 V/V. Gain can be configured individually for
each channel. The device can also be configured as
a second-order low-pass filter and is ideal for interfacing with PWM audio sources. Audio output
compiles with ±8-kV IEC ESD protection, requiring
just a simple resistor-capacitor ESD protection circuit.
The TPA6138A2 has built-in active-mute control for pop-free audio on/off control. The TPA6138A2 has an
external undervoltage detector that mutes the output
when the power supply is removed, ensuring a pop•
free shutdown.
Using the TPA6138A2 in audio products can reduce
component count considerably compared to
traditional headphone amplifiers. The TPA6138A2 does not require a split-rail power supply or a dc
blocking capacitor. The TPA6138A2 integrates its
own charge pump to generate a negative supply rail
that provides a clean, pop-free ground-biased audio
signal.
The TPA6138A2 is available in a 14-pin TSSOP.