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TPS54328

SLVSAN2D – NOVEMBER 2010 – REVISED AUGUST 2016

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Feature Description (continued)

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 returns to the regulated value. This protection is non-latching.

7.3.6 UVLO Protection

Undervoltage lock out protection (UVLO) monitors the voltage of the VREG5 pin. When the VREG5 voltage is

lower than UVLO threshold voltage, the TPS54328 is shut off. This protection is non-latching.

7.3.7 Thermal Shutdown

TPS54328 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.

7.4 Device Functional Modes

7.4.1 Normal Operation

When the input voltage is above the UVLO threshold and the EN voltage is above the enable threshold, the

TPS54328 can operate in the normal switching modes. Normal continuous conduction mode (CCM) occurs when

the minimum switch current is above 0 A. In CCM, the TPS54328 operates at a quasi-fixed frequency of

700 kHz.

7.4.2 Standby Operation

When the device is operating in either normal CCM or forced CCM, it may be placed in standby operation mode

by asserting the EN pin low.