Data Sheet

TB67S279FTG, TB67S289FTG, TB67S249FTG Application Note
2018-03-07
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Preliminary
(5) Carefully select external components (such as inputs and negative feedback capacitors) and load
components (such as speakers), for example, power amp and regulator.
If there is a large amount of leakage current such as from input or negative feedback condenser, the
IC output DC voltage will increase. If this output voltage is connected to a speaker with low input
withstand voltage, over current or IC failure may cause smoke or ignition. (The over current may
cause smoke or ignition from the IC itself.) In particular, please pay attention when using a Bridge
Tied Load (BTL) connection type IC that inputs output DC voltage to a speaker directly.
Points to remember on handling of ICs
(1) Over current protection Circuit
Over current protection circuits (referred to as current limiter circuits) do not necessarily protect
ICs under all circumstances. If the over current protection circuits operate against the over current,
clear the over current status immediately.
Depending on the method of use and usage conditions, exceeding absolute maximum ratings may
cause the over current protection circuit to operate improperly or IC breakdown may occur before
operation. In addition, depending on the method of use and usage conditions, if over current
continues to flow for a long time after operation, the IC may generate heat resulting in breakdown.
(2) Thermal Shutdown Circuit
Thermal shutdown circuits do not necessarily protect ICs under all circumstances. If the thermal
shutdown circuits operate against the over temperature, clear the heat generation status
immediately.
Depending on the method of use and usage conditions, exceeding absolute maximum ratings may
cause the thermal shutdown circuit to operate improperly or IC breakdown to occur before
operation.
(3) Heat Radiation Design
When using an IC with large current flow such as power amp, regulator or driver, design the
device so that heat is appropriately radiated, in order not to exceed the specified junction
temperature (Tj) at any time or under any condition. These ICs generate heat even during normal
use. An inadequate IC heat radiation design can lead to decrease in IC life, deterioration of IC
characteristics or IC breakdown. In addition, when designing the device, take into consideration
the effect of IC heat radiation with peripheral components.
(4) Back-EMF
When a motor rotates in the reverse direction, stops or slows abruptly, current flows back to the
motor’s power supply owing to the effect of back-EMF. If the current sink capability of the power
supply is small, the device’s motor power supply and output pins might be exposed to conditions
beyond the absolute maximum ratings. To avoid this problem, take the effect of back-EMF into
consideration in system design.