BD8649EFV Datasheet, PDF (12/14 Pages) Rohm – Flexible Step-down Switching Regulator with Built-in Power MOSFET

BD8649EFV
Technical Note
●Note for use
1. About the absolute maximum rating
Attention is brushed off enough to the quality control, it is likely to destroy when the absolute maximum rating such as
impressed voltages (VCC_IN,DCIN) and ranges (Topr) of the operating temperature as it is exceeded, the mode of
breakings of the short or the opening, etc. cannot be specified, and examine it in this IC to give physical measures for
safety such as fuses when a special mode that exceeds the absolute maximum rating is assumed.
2. GND pin voltage
GND terminal should be connected the lowest voltage, under all conditions. And all terminals except SW should be under
GND terminal voltage under all conditions including transient situations. If a terminal exists under GND,it should be
inserting a bypass route.
3. Power dissipation
If IC is used on condition that the power loss is over the power dissipation, the reliability will become worse by heat up, such
as reduced output current capability. Also, be sure to use this IC within a power dissipation range allowing enough of margin.
4. Input supply voltage
Input supply pattern layout should be as short as possible.
5. About the short and the miss-installation between terminals
Note the direction and the miss-registration of IC enough when you install it in the set substrate. IC might destroy it as
well as reversely connecting the power supply connector when installing it by mistake. Moreover, there is fear of destruction
when the foreign body enters between terminals, the terminal, the power supply, and grandeur and it is short-circuited.
6. About operation in strong electromagnetic field
In use in strong electromagnetic field, note that there is a possibility of malfunctioning.
7. About the inspection by the set substrate
It is likely to suffer stress to IC and discharge electricity every one process when you connect the capacitor with the pin
with low impedance when inspecting it in the set substrate. Moreover, detach it after connecting after the power supply is
turned off without fail when detaching it to G in the inspection process, inspecting, and turning off the power supply.
In addition, be give the earth to the assembly process as a static electricity measures, and careful enough when it
transports and you preserve it.
8. About each input terminal
This IC is a monolithic IC which has a P⁺ isolations and P substrate to isolate elements each other.
This P layer and an N layer in each element form a PN junction to construct various parasitic elements.
For instance, the potential difference operates in resistance as shown in the figure below when resistance and the
transistor connect it with the terminal and the playground (GND) >(terminal B) joint of PN operates as a parasitic diode in
playground (GND) >(terminal A) transistor (NPN). In addition, the NPN transistor of parasitism works with N layer of the
element of the above-mentioned parasitic diode and the neighborhood and others in transistor (NPN). A parasitic element
in IC composition is inevitably formed because of the potential relation.
A parasitic element can operate, the interference with the circuit operation be caused, it malfunction, and, consequently, it
cause destruction. Therefore, do not do the usage that a parasitic element operates as a voltage that is lower than the
playground (GND; P substrate) is impressed to the input terminal enough. Moreover, do not impress the voltage to the input
terminal when you do not impress the power-supply voltage to IC. Give each input terminal to me the voltage below the
power-supply voltage or in the guarantee value of an electric characteristic when you similarly impress the power-supply
voltage.
Terminal A
Resistance
Termin
al
A
Terminal B
C
Transistor ( NPN)
B
E
TerminalB
BC
E
P⁺
P P⁺
Parasitic
element
P⁺
P
P⁺
Terminal of
neighborhood and
Parasitic
P Substrate
P Substrate
others
element
GND
Parasitic
element
GND
Parasitic
element
GND
GND
Example of IC of simple structure
9. Earth wiring pattern
If small signal GND and large current GND exist, disperse their pattern. In addition, for voltage change by pattern wiring
impedance and large current not to change voltage of small signal GND, each ground terminal of IC must be connected
at the one point on the set circuit board. As for GND of external parts, it is similar to the above-mentioned.
10. About each output terminal
We recommend to put Diode for protection purpose in case of output pin connected with large load of impedance or
reserve current occurred at initial and output off.
11. Thermal Shut Down Circuit
A temperature control is built in the IC to prevent the damage due to overheat. Therefore, the outputs are turned off when
the thermal circuit works.
12. Over Output Current Protection
SW Output terminal has over current protection circuit of 5A, with prevents IC from being damage by short circuit at over
current. However, It is recommend not to use that continuously operates the protection circuit (For instance, always the
load that greatly exceeds the output current ability is connected or the output is short-circuited, etc.) in these protection
circuits by an effective one to the destruction prevention due to broken accident.
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12/13
2010.09 - Rev.A