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TPA2039D1

www.ti.com

SLOS652A – DECEMBER 2009 – REVISED JUNE 2010

APPLICATION INFORMATION

SHORT CIRCUIT AUTO-RECOVERY

When a short-circuit event occurs, the TPA2039D1 goes to shutdown mode and activates the integrated

auto-recovery process whose aim is to return the device to normal operation once the short-circuit is removed.

This process repeatedly examines (once every 100ms) whether the short-circuit condition persists, and returns

the device to normal operation immediately after the short-circuit condition is removed. This feature helps protect

the device from large currents and maintain a good long-term reliability.

INTEGRATED IMAGE REJECT FILTER FOR DAC NOISE REJECTION

In applications which use a DAC to drive Class-D amplifiers, out-of-band noise energy present at the DAC's

image frequencies fold back into the audio-band at the output of the Class-D amplifier. An external low-pass filter

is often placed between the DAC and the Class-D amplifier in order to attenuate this noise.

The TPA2039D1 has an integrated Image Reject Filter with a low-pass cutoff frequency of 130 kHz, which

significantly attenuates this noise. Depending on the system noise specification, the integrated Image Reject

Filter may help eliminate external filtering, thereby saving board space and component cost.

COMPONENT SELECTION

Figure 28 shows the TPA2039D1 typical schematic with differential inputs, while Figure 29 shows the

TPA2039D1 with differential inputs and input capacitors. Figure 30 shows the TPA2039D1 with a single-ended

input.

The TPA2039D1 is a high-performance class-D audio amplifier that requires adequate power supply decoupling

to ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients,

for the efficiency of the class-D amplifier, because any resistance or inductance in the trace between the device

and the capacitor can cause a loss in efficiency. For filtering lower-frequency noise signals, a 10 mF or greater

because of the high PSRR of this device. Typically, the smaller the capacitor's case size, the lower the

inductance and the closer it can be placed to the TPA2039D1. X5R and X7R dielectric capacitors are

The TPA2039D1 does not require input coupling capacitors if the design uses a differential source that is biased

within the common-mode input voltage range. That voltage range is listed in the Recommended Operating

Conditions table. If the input signal is not biased within the recommended common-mode input range, such as in

needing to use the input as a high pass filter, shown in Figure 29, or if using a single-ended source, shown in

Figure 30, input coupling capacitors are required. The same value capacitors should be used on both IN+ and

(1)

The value of the input capacitor is important to consider as it directly affects the bass (low frequency)

performance of the circuit. Speaker response may also be taken into consideration when setting the corner

frequency using input capacitors. Solving for the input coupling capacitance, we get:

(2)

If the corner frequency is within the audio band, the capacitors should have a tolerance of ±10% or better,

because any mismatch in capacitance causes an impedance mismatch at the corner frequency and below.

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