IRAUDAMP7D Datasheet, PDF (24/43 Pages) International Rectifier – 25W-500W Scalable Output Power Class D Audio Power Amplifier Reference Design Using the IRS2092 Protected Digital Audio Driver

Over-Current Protection (OCP)
Low-Side Current Sensing
The low-side current sensing feature protects the low side MOSFET from an overload condition in negative
load current by measuring drain-to-source voltage across R_DS(ON) during its on state. OCP shuts down the
switching operation if the drain-to-source voltage exceeds a preset trip level.
The voltage setting on the OCSET pin programs the threshold for low-side over-current sensing. When the
VS voltage during low-side conduction gets higher than the OCSET voltage, the IRS2092 turns off outputs
and pulls CSD down to -VSS.
High-Side Current Sensing
The high-side current sensing protects the high side MOSFET from an overload condition in
positive load current by measuring drain-to-source voltage across R_DS(ON) during its on state. OCP
shuts down the switching operation if the drain-to-source voltage exceeds a preset trip level.
High-side over-current sensing monitors drain-to-source voltage of the high-side MOSFET while it
is in the on state through the CSH and VS pins. The CSH pin detects the drain voltage with
reference to the VS pin, which is the source of the high-side MOSFET. In contrast to the low-side
current sensing, the threshold of CSH pin to trigger OC protection is internally fixed at 1.2V. An
external resistive divider R19, R18 and R17 are used to program a threshold as shown in Fig 26.
An external reverse blocking diode D4 is required to block high voltage feeding into the CSH pin
during low-side conduction. By subtracting a forward voltage drop of 0.6V at D4, the minimum
threshold which can be set for the high-side is 0.6V across the drain-to-source.
Table 2 Actual OCP table setting thresholds
Function
Device
OCSET
R12A
R12B
Tested OCP current 25^oC
CSH
R18A
R18B
Tested OCP current 25^oC
Peak load current
at rated power
Amp7-55
1.3K
0.0
6.0A
Amp7-100
3.9K
23A
4.7K
23A
8.7A
Amp7-150
7.5K
30A
9.6K
29A
12.2A
Amp7-200
5.2K
23A
8.2K
23A
8.9A
Over-Voltage Protection (OVP)
OVP is provided externally to the IRS2092. OVP shuts down the amplifier if the bus voltage
between GND and +B exceeds 75V. The threshold is determined by a Zener diode Z100. OVP
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IRAUDAMP7D REV 2.8
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