STA515W

Applications information

Doc ID 11079 Rev 2

9/14

Protection circuits

The STA515W includes protection circuitry for overcurrent and thermal overload conditions.

A thermal warning pin (THWARN) is activated low (open-drain MOSFET) when the IC

temperature exceeds 130 °C, which is 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 the high-impedance state. At the same time an

open-drain MOSFET connected to pin FAULT is switched on.

There are two possible modes subsequent to activating a fault:

Shutdown mode:

with pins FAULT (with pull-up resistor) and TRISTATE independent, an activated fault

disables the device, signalling low at pin FAULT.

The device may subsequently be reset to normal operation by toggling pin TRISTATE

from high to low and back to high using an external logic signal.

Automatic recovery mode:

This is shown in the applications circuit in Figure 7 and Figure 7 on page 10.

Pins FAULT and TRISTATE are shorted together and connected to a time constant

circuit comprising R59 and C58.

An activated fault forces a reset on pin TRISTATE 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 continues, repeating until the

fault condition is removed.

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

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

thresholds under normal operation.

Power outputs

The STA515W power and output pins are duplicated to provide a low-impedance path for

the device bridged outputs. All duplicated power, ground and output pins must be connected

for proper operation.

Pins PWRDN or TRISTATE should be used to set all MOSFETS to the high-impedance

state during power-up and until the logic power supply, VL, has settled.

Parallel-output and high-current operation

When using DDX mode, the STA515W outputs can be connected in parallel to increase the

output current capability. In this configuration the device can provide 40 W into 8

Ω.

This mode of operation is enabled with pin CONFIG connected to VDD. The inputs must be

combined to give INLA = INLB and INRA = INRB, then the corresponding outputs can be

shorted together to give OUTLA = OUTLB and OUTRA = OUTRB.

Output filter

A passive 2nd-order filter is used on the STA515W power outputs to reconstruct an analog

audio signal. The system performance can be significantly affected by the output filter

design and choice of passive components.

Filter designs for 4-

Ω and 8-Ω loads are shown in the applications circuits of Figure 1 on

page 2 for the half-bridge mode, and Figure 7 and Figure 8 on page 10 for the full bridge.