TB7101AF Datasheet, PDF (12/22 Pages) Toshiba Semiconductor – Buck DC-DC Converter IC

TB7101AF(T5L1.2,F)/(T5L1.5,F)/(T5L1.8,F)/(T5L2.5,F)/(T5L3.3,F)
Thermal Shutdown (TSD)
The TB7101AF provides thermal shutdown. When the junction temperature continues to rise and reaches T_SD
(160°C typ.), the TB7101AF goes into thermal shutdown and shuts off the power supply. TSD has a hysteresis of
about 20°C. The device is enabled again when the junction temperature has dropped by approximately 20°C from
the TSD trip point. The device resumes the power supply when the soft-start circuit is used upon recovery from
the TSD state.
Thermal shutdown is intended to protect the device against abnormal system conditions. It should be ensured
that the TSD circuit will not be activated during normal operation of the system.
TSD Detection threshold: T_SD
T_j
0
V_OUT
GND
Switching operation stops
Recovery from TSD
Hysteresis: ΔT_SD
Switching operation starts
Soft start
Figure 5 Thermal Shutdown Operation
Usage Precautions
• The input voltage, output voltage, output current and temperature conditions should be considered when
selecting capacitors and inductors. These components should be evaluated on an actual system prototype for best
selection.
• External components such as capacitors and inductor should be placed as close to the TB7101AF as possible.
• The TB7101AF has an ESD diode between the EN and V_IN pins. The voltage between these pins should satisfy
V_EN − V_IN < 0.3 V.
• Operation might become unstable due to board layout. In that case, add a decoupling capacitor (C_C) of 0.1 μF to
1μF between the SGND and V_IN pins.
• The overcurrent protection circuits in the Product are designed to temporarily protect Product from minor
overcurrent of brief duration. When the overcurrent protective function in the Product activates, immediately
cease application of overcurrent to Product. Improper usage of Product, such as application of current to Product
exceeding the absolute maximum ratings, could cause the overcurrent protection circuit not to operate properly
and/or damage Product permanently even before the protection circuit starts to operate.
• The thermal shutdown circuits in the Product are designed to temporarily protect Product from minor
overheating of brief duration. When the overheating protective function in the Product activates, immediately
correct the overheating situation. Improper usage of Product, such as the application of heat to Product
exceeding the absolute maximum ratings, could cause the overheating protection circuit not to operate properly
and/or damage Product permanently even before the protection circuit starts to operate.
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2008-05-22