TPA3131D2, TPA3132D2

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SLOS841B – SEPTEMBER 2013 – REVISED JANUARY 2015

7.3.6 BSPx and BSNx 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 220 nF ceramic capacitor of quality X5R or better, rated for at

least 16 V, must be connected from each output to its corresponding bootstrap input. (See the application circuit

diagram in Figure 29.) 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.

7.3.7 Differential Inputs

The differential input stage of the amplifier cancels any noise that appears on both input lines of the channel. To

use the TPA313xD2 with a differential source, connect the positive lead of the audio source to the RINP or LINP

input and the negative lead from the audio source to the RINN or LINN input. To use the TPA313xD2 with a

single-ended source, ac ground the negative input through a capacitor equal in value to the input capacitor on

positive 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 10 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.

7.3.8 Device Protection System

The TPA313xD2 contains a complete set of protection circuits carefully designed to make system design efficient

as well as to protect the device against any kind of permanent failures due to short circuits, overload, over

temperature, and under-voltage. The FAULTZ pin will signal if an error is detected according to the fault table

below:

Table 4. Fault Reporting

TRIGGERING CONDITION

LATCHED/SELF-

FAULT

FAULTZ

ACTION

(typical value)

CLEARING

Over Current

Output short or short to PVCC or GND

Low

Output high impedance

Latched

Over Temperature

Low

Output high impedance

Latched

Too High DC Offset

DC output voltage

Low

Output high impedance

Latched

Under Voltage on

PVCC < 4.5V

–

Output high impedance

Self-clearing

PVCC

Over Voltage on

PVCC > 27V

–

Output high impedance

Self-clearing

PVCC

7.3.9 DC Detect Protection

The TPA313xD2 has circuitry which will protect the speakers from DC current which might occur due to defective

capacitors on the input or shorts on the printed circuit board at the inputs. A DC detect fault will be reported on

the FAULT pin as a low state. The DC Detect fault will also cause the amplifier to shutdown by changing the

state of the outputs to Hi-Z.

If automatic recovery from the short circuit protection latch is desired, connect the FAULTZ pin directly to the

SDZ pin. This allows the DC Protection function to automatically drive the SDZ pin low which clears the DC

Detect protection latch.

A DC Detect Fault is issued when the output differential duty-cycle of either channel exceeds 60% for more than

420 msec at the same polarity. Table x below shows some examples of the typical DC Detect Protection

threshold for several values of the supply voltage. This feature protects the speaker from large DC currents or

AC currents less than 2Hz. To avoid nuisance faults due to the DC detect circuit, hold the SD pin low at power-

up until the signals at the inputs are stable. Also, take care to match the impedance seen at the positive and

negative inputs to avoid nuisance DC detect faults.

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