High-Power Stereo Class-D Audio Power Amplifier
SGM4703 with Adjustable Power Limit and Automatic Level Control
24
DECEMBER 2022
SG Micro Corp
www.sg-micro.com
APPLICATION INFORMATION (continued)
Protection Modes
For safe operation, the SGM4703 incorporates
comprehensive protection circuits against various
operating faults including Under-Voltage, Over-Voltage,
Over-Current, Over-Temperature, and DC-Detect, as
described in Table 7. In the shutdown mode, all the
analog circuitry is de-biased with differential outputs to
be shorted to ground. In the mute mode, all the analog
circuitry is enabled with differential outputs to be
shorted to ground.
Under-Voltage Lockout (UVLO)
The SGM4703 incorporates circuitry to detect a low
supply voltage for safe and reliable operation. When
the supply voltage is first applied, the SGM4703 will
remain inactive until the supply voltage exceeds 4.6V
(V
UVLOUP
). When the supply voltage is removed and
drops below 4.3V (V
UVLODN
), the SGM4703 enters into
mute mode, where the differential audio outputs
VOPL/R and VONL/R are pulled to ground through
on-chip resistors (5kΩ) individually.
Over-Voltage Protection (OVP)
The SGM4703 features over-voltage protection. When
the supply voltage exceeds 28V (V
OVPUP
), the device
enters into mute mode, where the differential audio
outputs VOPL/R and VONL/R are pulled to ground
through on-chip resistors (5kΩ) individually. The device
will resume normal operation once the supply voltage
returns to a value lower than 26.5V (V
OVPDN
).
Over-Temperature Shutdown (OTSD)
When the die temperature exceeds +160℃, the device
enters into mute mode, where the differential audio
outputs VOPL/R and VONL/R are pulled to ground
through on-chip resistors (5kΩ) individually. The device
will resume normal operation once the die temperature
returns to a lower temperature, which is about 20℃
lower than the threshold.
DC-Detect Protection (DCP)
The SGM4703 features DCP circuit to protect the
speakers from large DC current. A DC-detect fault is
issued when the duty cycle of differential outputs of
either channel exceeds 20% for more than 720ms at
the same polarity. The device enters into mute mode,
where the differential audio outputs VOPL/R and
VONL/R are pulled to ground through on-chip resistors
(5kΩ) individually. Note that the DCP threshold is a
function of the supply voltage, as shown in Table 8. To
avoid nuisance faults due to the DCP circuit, it is
recommended to hold the EN pin low during startup
until the audio signals at the inputs are stable. Also,
take care to closely match the impedance seen at two
differential inputs.
A DC-detect fault is latched and reported on the
FAULTB pin as a low state. Also, the SGM4703 enters
into mute mode and remains in mute mode. The latch
can be cleared by cycling the EN pin through the low
state.
Over-Current Protection (OCP)
In operation, the outputs of Class-D amplifiers are
constantly monitors for any over-current and/or
short-circuit conditions. When a short-circuit condition
between two differential outputs, differential outputs to
PVDD or ground is detected, the device enters into
mute mode, where the differential audio outputs
VOPL/R and VONL/R are pulled to ground through
on-chip resistors (5kΩ) individually. If the fault persists
over a prescribed period, the fault condition is latched
and reported on the FAULTB pin as a low state. Also,
the SGM4703 enters into mute mode and remains in
mute mode. The latch can be cleared by cycling the EN
pin through the low state.
If automatic recovery from the OCP fault is desired,
connect the FAULTZ pin directly to the EN pin, as shown
in Figure 13. It allows the FAULTZ pin to automatically
drive the EN pin low, which clears the OCP latch.
Table 7. Protection Modes of Various Operating faults
Fault Detection Condition FAULTB Audio Outputs Mode
Over-Current
Audio outputs shorted to PVDD or
GND or each other
Low 5kΩ to GND Mute Latched
DC-Detect See Table 8 Low 5kΩ to GND Mute Latched
Over-Temperature
T
J
> 160℃
- 5kΩ to GND Mute Self-Recovery
Under-Voltage PVDD < 4.3V - 5kΩ to GND Mute Self-Recovery
Over-Voltage PVDD > 28V - 5kΩ to GND Mute Self-Recovery
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