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TPA3126D2

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SLOS942 – APRIL 2018

Product Folder Links: TPA3126D2

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Copyright © 2018, Texas Instruments Incorporated

8.3.8 Device Protection System

The TPA3126D2 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 signals if an error is detected according to Table 4:

Table 4. Fault Reporting

FAULT

TRIGGERING CONDITION

(typical value)

FAULTZ

ACTION

LATCHED/SELF-

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

PVCC < 4.5V

–

Output high impedance

Self-clearing

Over Voltage on

PVCC

PVCC > 27V

–

Output high impedance

Self-clearing

8.3.9 DC Detect Protection

The TPA3126D2 has circuitry which protects 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 is reported on the

FAULT pin as a low state. The DC Detect fault causes 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. Connecting the FAULTZ and SDZ pins allows the FAULTZ pin 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 voltage of either channel exceeds DC protection

threshold level for more than 640 ms at the same polarity. Table 5 shows some examples of the typical DC

Detect Protection threshold for several values of the supply voltage. The Detect Protection Threshold feature

protects the speaker from large DC currents or AC currents less than 2 Hz. 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.

Table 5 lists the minimum output offset voltages required to trigger the DC detect. The outputs must remain at or

above the voltage listed in the table for more than 640 ms to trigger the DC detect.

Table 5. DC Detect Threshold

4.5

1.35

6

1.8

12

3.6

18

5.4

8.3.10 Short-Circuit Protection and Automatic Recovery Feature

The TPA3126D2 has protection from over current conditions caused by a short circuit on the output stage. The

short circuit protection fault is reported on the FAULTZ pin as a low state. The amplifier outputs are switched to a

high impedance state when the short circuit protection latch is engaged. The latch can be cleared by cycling the

SDZ pin through the low state.

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

SDZ pin. Connecting the FAULTZ and SDZ pins allows the FAULTZ pin function to automatically drive the SDZ

pin low which clears the short-circuit protection latch.