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Page 13 of 50
IRAUDAMP5 REV 3.1
Internal Faults
OCP and OTP are considered internal faults, which 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,
Fig 14
)
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 the
CSD pin low 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, which is
limited by the PCB material and not by the operating range of the MOSFET.
R31
100K
Rp1
100C
-B
C28
47nF
R48
1K
R47
100K
Q7
OTP CH1
-B
OTP1
Rp1 is thermally connected with Q3
3
2
1
2
3
Q3
IRF6645
Fig 14
Over-Current Protection (OCP)
The OCP internal to the IRS2092S 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 IRS2092S
datasheet. Here is a brief description:
Low-Side Current Sensing
Fig 15 shows the low side MOSFET as is protected from an overload condition by measuring the
low side MOSFET drain-to-source voltage during the low side MOSFET on state, and will shut
down the switching operation if the load current exceeds a preset trip level. The voltage setting on
the OCSET pin programs the threshold for low-side over-current sensing. Thus, if the VS voltage
during low-side conduction is higher than the OCSET voltage, the IRS2092S will trip and CSD
goes down. It is recommended to use VREF to supply a reference voltage to a resistive divider
(R19 and R18 for CH1) to generate a voltage to OCSET; this gives better variability against VCC
fluctuations. For IRAUDAMP5, the low-side over-current trip level is set to 0.65V. For IRF6645
DirectFET MOSFETs with a nominal R
DS-ON
of 28mOhms at 25
°
C, this results in a ~23A
maximum trip level. Since the R
DS-ON
is a function of temperature, the trip level is reduced to
~15A at 100
°
C.
Summary of Contents for IRAUDAMP5
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