TPA3116D2-Q1, TPA3118D2-Q1

SLOS862A – JULY 2015 – REVISED AUGUST 2015

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7.3.9 DC-Detect Protection

The TPA311xD2-Q1 family 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 also causes the amplifier to shut down by changing the

state of the outputs to Hi-Z.

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

pin. This allows the FAULT pin function to automatically drive the SD 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 ms at the same polarity. For several values of the supply voltage, Table 6 shows some examples of the

typical output offset voltages that trigger dc-detect protection. This 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 6 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 420 ms to trigger the dc detect.

Table 6. DC Detect Threshold

4.5

0.96

6

1.3

12

2.6

18

3.9

7.3.10 Short-Circuit Protection and Automatic Recovery Feature

The TPA311xD2-Q1 family has protection from overcurrent conditions caused by a short circuit on the output

stage. The short-circuit protection fault is reported on the FAULT 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 SD pin through the low state.

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

pin. This allows the FAULT pin function to automatically drive the SD pin low, which clears the short-circuit

protection latch.

In systems where a possibility of a permanent short from the output to PVDD or to a high-voltage battery like a

car battery can occur, pull the MUTE pin low with the FAULT signal and an inverting transistor to ensure a high-Z

restart, as shown in Figure 15.

14

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