DocID010708 Rev 6

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STA518

Technical information

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temperature exceeds 130 °C, in advance of the thermal shutdown protection. When a fault

condition is detected, an internal fault signal acts to immediately disable the output power

MOSFETs, placing both H-Bridges in high impedance state. At the same time an open-drain

MOSFET connected to the FAULT pin (pin 27) is switched on.

There are two possible modes subsequent to activating a fault:

1.

SHUTDOWN mode: with FAULT (pull-up resistor) and TRI-STATE pins independent,

an activated fault will disable the device, signaling low at the FAULT output.

The device may subsequently be reset to normal operation by toggling the TRI-STATE

pin from high to low to high using an external logic signal.

2.

AUTOMATIC recovery mode: This is shown in the audio application circuit of quad

single-ended. The FAULT and TRI-STATE pins are shorted together and connected to

a time constant circuit comprising R59 and C58.

An activated FAULT will force a reset on the TRI-STATE pin causing normal operation

to resume following a delay determined by the time constant of the circuit.

If the fault condition is still present, the circuit operation will continue repeating until the

fault condition is removed.

An increase in the time constant of the circuit will produce a longer recovery interval.

Care must be taken in the overall system design as not to exceed the protection

thresholds under normal operation.

4.2

Power outputs

The STA518 power and output pins are duplicated to provide a low impedance path for the

device's bridged outputs. All duplicate power, ground and output pins must be connected for

proper operation.

The PWRDN or TRI-STATE pins should be used to set all MOSFETS to the Hi-Z state

during power-up until the logic power supply, VL, is settled.

4.3

Parallel output / high current operation

When using DDX mode output, the STA518 outputs can be connected in parallel in order to

increase the output current capability to a load. In this configuration the STA518 can provide

70 W into 8 ohm.

This mode of operation is enabled with the CONFIG pin (pin 24) connected to VREG1 and

the inputs combined INLA=INLB, INRA=INRB and the outputs combined OUTLA=OTLB,

OUTRA=OUTRB.

4.4

Additional information

Output Filter: A passive 2nd order passive filter is used on the STA518 power outputs to

reconstruct an analog audio signal. System performance can be significantly affected by the

output filter design and choice of passive components. A filter design for 6 ohm / 8 ohm

loads is shown in the typical application circuit of Figure 9.

Quad single-ended circuit (Figure 1) shows a filter for half-bridge mode, 4 ohm loads.