SLVSAZ6A – SEPTEMBER 2011 – REVISED MARCH 2012
cycle begins. In subsequent switching cycles, the on-time is set to a fixed value and the current is monitored in
the same manner. If the over current condition exists for 7 consecutive switching cycles, the internal OCL
threshold is set to a lower level, reducing the available output current. When a switching cycle occurs where the
switch current is not above the lower OCL threshold, the counter is reset and the OCL limit is returned to the
higher value.
There are some important considerations for this type of over-current protection. The load current one half of the
peak-to-peak inductor current higher than the over-current threshold. Also when the current is being limited, the
output voltage tends to fall as the demanded load current may be higher than the current available from the
converter. This may cause the output voltage to fall. When the over current condition is removed, the output
voltage will return to the regulated value. This protection is non-latching.
UVLO Protection
Undervoltage lock out protection (UVLO) monitors the voltage of the V
REG5
pin. When the V
REG5
voltage is lower
than UVLO threshold voltage, the TPS54329 is shut off. This is protection is non-latching.
Thermal Shutdown
TPS54329 monitors the temperature of itself. If the temperature exceeds the threshold value (typically 165°C),
the device is shut off. This is non-latch protection.
8
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