BD95242MUV_10 Datasheet, PDF (18/21 Pages) Rohm – 2ch Switching Regulator for Desktop PC

Technical Note
●Operation Notes and Precautions
1. This integrated circuit is a monolithic IC, which (as shown in the figure below), has P isolation in the P substrate and
between the various pins. A P-N junction is formed from this P layer and N layer of each pin, with the type of junction
depending on the relation between each potential, as follows:
・When GND＞ element A＞ element B, the P-N junction is a diode.
・When element B＞GND element A, the P-N junction operates as a parasitic transistor.
Parasitic diodes inevitably occur in the structure of the IC. The operation of parasitic diodes can result in mutual
interference among circuits, as well as operating malfunctions and physical damage. Therefore, be careful to avoid
methods by which parasitic diodes operate, such as applying a voltage lower than the GND (P substrate) voltage to an
input pin.
Pin A
N
N ^P+
Parasitic element
Resistor
Pin A
P
P⁺ _N
P substrate
GND
Transistor (NPN)
Pin B _C B
Pin B
E
Parasitic
element
N _P+
Parasitic element
N
P
P⁺ _N
P substrate
GND
GND
B
C
E
Parasitic
element
GND
Other adjacent elements
2. In some modes of operation, power supply voltage and pin voltage are reversed, giving rise to possible internal circuit
damage. For example, when the external capacitor is charged, the electric charge can cause a VCC short circuit to the
GND. In order to avoid these problems, inserting a VCC series countercurrent prevention diode or bypass diode between
the various pins and the VCC is recommended.
Bypass diode
Countercurrent
VCC
Pin
3. Absolute maximum rating
Although the quality of this IC is rigorously controlled, the IC may be destroyed when applied voltage or operating
temperature exceeds its absolute maximum rating. Because short mode or open mode cannot be specified when the IC is
destroyed, it is important to take physical safety measures such as fusing if a special mode in excess of absolute rating
limits is to be implemented.
4.GND potential
Make sure the potential for the GND pin is always kept lower than the potentials of all other pins, regardless of the
operating mode.
5. Thermal design
In order to build sufficient margin into the thermal design, give proper consideration to the allowable loss (Power
Dissipation) in actual operation.
6. Short-circuits between pins and incorrect mounting position
When mounting the IC onto the circuit board, be extremely careful about the orientation and position of the IC. The IC may
be destroyed if it is incorrectly positioned for mounting. Do not short-circuit between any output pin and supply pin or
ground, or between the output pins themselves. Accidental attachment of small objects on these pins will cause shorts and
may damage the IC.
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18/20
2010.03 - Rev.C