BD9845FV Datasheet, PDF (14/16 Pages) Rohm – Single/Dual-output High-frequency Step-down Switching Regulator(Controller type)

BD9845FV
Technical Note
●Notes for use
1) About maximum absolute rating
When the maximum absolute rating of application voltage or operation voltage range is exceeded, it may lead to
deterioration or rupture. It is impossible to forecast rupture in short mode or open mode. When a special mode is expected
exceeding the maximum absolute rating, try to take a physical safety measure such as a fuse.
2) GND potential
Ensure that the potential of GND terminal is the minimum in any operation condition. Also ensure that no terminal except
GND terminal has a voltage below GND voltage including actual transient phenomenon.
3) Thermal design
Allow a sufficient margin in thermal design in consideration of permissible loss (Pd) in actual use condition.
4) Shorting between terminals and wrong attachment
When attaching an IC to a set board, pay full attention to the direction of IC and dislocation. Wrong attachment may cause
rupture of IC. In addition, when shorting is caused by foreign substance placed between outputs or between output and
power supply-GND, rupture is also possible.
5) Operation in intense magnetic field
Use in intense magnetic field may result in malfunction. Be careful.
6) Inspection on set board
In inspection on set board, when a capacitor is connected to a terminal with low impedance, stress may be applied to IC,
therefore be sure to discharge electricity in each process. Apply grounding to assembling process for a measure against
static electricity, and take enough care in transport and storage. When connecting a jig in inspection process, be sure to
turn off power before detaching IC.
7) About IC terminal input
This IC is a monolithic IC, and contains P⁺ isolation and P board for separating elements between each element. This
P-layer and N-layer of each element form P-N junction, and many kinds of parasitic elements are constituted. (See Fig 43.)
For example, when resistor and transistor are connected with a terminal as shown below.
○P-N junction operates as a parasitic diode when
GND>(Terminal A) for resistor, and when GND>(Terminal B) for transistor (NPN).
○In addition, when GND>(Terminal B) for transistor (NPN),
parasitic NPN transistor is operated by N-layer of some other elements in the vicinity of parasitic diode mentioned above.
Parasitic element is inevitably generated by potential because of IC structure. Operation of parasitic element causes
interference with circuit operation, and may lead to malfunction, and also may cause rupture. Therefore when applying a
voltage lower than GND (P board) to I/O terminal, pay full attention to usage so that parasitic elements do not operate.
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14/15
2009.05 - Rev.A