International Rectifier IRAUDAMP4, Manual

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RD-0617
Protection
The IRAUDAMP4 has a number of protection circuits to safeguard the system and
speaker during operation, which fall into one of two categories, internal faults and
external faults, and distinguished by the manner in which a fault condition is treated.
Internal faults are only relevant to the particular channel, while external faults affect the
whole board. For internal faults, only the offending channel is stopped. The channel will
hiccup until the fault is cleared. For external faults, the whole board is stopped using the
shutdown sequencing described earlier. Here, the system will also hiccup until the fault
is cleared at which time it will restart according to the startup sequencing described
earlier.
20955 PWM
OCP
OVP/
UVP
DCP
Red
LED
-B
+B
Trip
-B
VCC
OTP
Green
LED
To other Channel
CSD
Figure 13. Functional Block Diagram of Protection Circuit Implementation
Internal Faults
OCP and OTP are considered internal faults. These internal faults will only shutdown the
particular channel by pulling low the relevant CSD pin. The channel will shutdown for
about one-half a second and will hiccup until the fault is cleared.
Over-Temperature Protection (OTP)
A separate PTC resistor is placed in close proximity to the high-side IRF6645 DirectFET
MOSFET for each of the amplifier channels. If the resistor temperature rises above
100
°
C, the OTP is activated. The OTP protection will only shutdown the relevant
channel by pulling low the CSD pin and will recover once the temperature at the PTC
has dropped sufficiently. This temperature protection limit yields a PCB temperature at
the MOSFET of about 100
°
C. This setting is limited by the PCB material and not by the
operating range of the MOSFET.
Over-Current Protection (OCP)
The OCP internal to the IRS20955 shuts down the IC if an OCP is sensed in either of the
output MOSFETs. For a complete description of the OCP circuitry, please refer to the
IRS20955 datasheet. Here is a brief description: