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MSTR/SLV and SYNC operation

USING LOW-ESR CAPACITORS

SHORT-CIRCUIT PROTECTION AND AUTOMATIC RECOVERY FEATURE

THERMAL PROTECTION

TPA3107D2

SLOS509A – OCTOBER 2006 – REVISED NOVEMBER 2006

The MSTR/SLV and SYNC terminals can be used to synchronize the frequency of the class-D output switching.

When the MSTR/SLV terminal is high, the output switching frequency is determined by the selection of the

resistor connected to the ROSC terminal (see ROSC Resistor Selection). The SYNC terminal becomes an

output in this mode, and the frequency of this output is also determined by the selection of the ROSC resistor.

This TTL compatible, push-pull output can be connected to another TPA3107D2, configured in the slave mode.

The output switching is synchronized to avoid any beat frequencies that could occur in the audio band when two

class-D amplifiers in the same system are switching at slightly different frequencies.

When the MSTR/SLV terminal is low, the output switching frequency is determined by the incoming square wave

on the SYNC input. The SYNC terminal becomes an input in this mode and accepts a TTL compatible square

wave from another TPA3107D2 configured in the master mode or from an external GPIO. If connecting to an

external GPIO, recommended frequencies are 200 kHz to 300 kHz for proper device operation, and the

maximum amplitude is 4 V.

Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal)

capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this

resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this

resistance, the more the real capacitor behaves like an ideal capacitor.

The TPA3107D2 has short-circuit protection circuitry on the outputs that prevents damage to the device during

outputs, the part immediately disables the output drive. This is a latched fault and must be reset by cycling the

voltage on the SHUTDOWN pin or MUTE pin. This clears the short-circuit flag and allows for normal operation if

the short was removed. If the short was not removed, the protection circuitry again activates.

The FAULT terminal can be used for automatic recovery from a short-circuit event, or used to monitor the status

with an external GPIO. For automatic recovery from a short-circuit event, connect the FAULT terminal directly to

the MUTE terminal. When a short-circuit event occurs, the FAULT terminal transitions high indicating a

short-circuit has been detected. When directly connected to MUTE, the MUTE terminal transitions high, and

clears the internal fault flag. This causes the FAULT terminal to cycle low, and normal device operation resumes

if the short-circuit is removed from the output. If a short remains at the output, the cycle continues until the short

is removed. If external MUTE control is desired, and automatic recovery from a short-circuit event is also

desired, an OR gate can be used to combine the functionality of the FAULT output and external MUTE control,

see Figure 27.

Thermal protection on the TPA3107D2 prevents damage to the device when the internal die temperature

exceeds 150

°C. There is a ±15°C tolerance on this trip point from device to device. Once the die temperature

exceeds the thermal set point, the device enters into the shutdown state and the outputs are disabled. This is

not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 30

°C. The device

begins normal operation at this point with no external system interaction.

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