TPS54427

SLVSB43

– NOVEMBER 2011

www.ti.com

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 VREG5 pin. When the VREG5 voltage is

lower than UVLO threshold voltage, the TPS54427 is shut off. This protection is non-latching.

Thermal Shutdown

TPS54427 monitors the temperature of itself. If the temperature exceeds the threshold value (typically 170

°C),

the device is shut off. This is non-latch protection.

TYPICAL CHARACTERISTICS

Figure 1. VIN CURRENT vs JUNCTION TEMPERATURE

Figure 2. VIN SHUTDOWN CURRENT vs JUNCTION

TEMPERATURE

Figure 3. EN CURRENT vs EN VOLTAGE

Figure 4. 1.05V OUTPUT VOLTAGE vs OUTPUT CURRENT

8

Submit Documentation Feedback

Copyright

© 2011, Texas Instruments Incorporated

Product Folder Link(s) :TPS54427