BD9853AFV Datasheet, PDF (15/17 Pages) Rohm – Single/Dual-output High-frequency Step-down Switching Regulato (Controller type)

BD9853AFV
Technical Note
12) IC pin input
This monolithic IC contains P+ isolation and PCB layers between adjacent elements in order to keep them isolated.
P/N junctions are formed at the intersection of these P layers with the N layers of other elements to create a variety of
parasitic elements. For example, when a resistor and transistor are connected to pins as shown in following chart,
 the P/N junction functions as a parasitic diode
when GND > (Pin A) for the resistor or GND > (Pin B) for the transistor (NPN).
 Similarly, when GND > (Pin B) for the transistor (NPN),
the parasitic diode described above combines with the N layer of other adjacent elements to operate as a parasitic
NPN transistor.
The formation of parasitic elements as a result of the relationships of the potentials of different pins is an inevitable result
of the IC's architecture. The operation of parasitic elements can cause interference with circuit operation as well as IC
malfunction and damage. For these reasons, it is necessary to use caution so that the IC is not used in a way that will
trigger the operation of parasitic elements, such as by the application of voltages lower than the GND (PCB) voltage to
input and output pins.
(PinA)
Resistance
Ｐ^＋
ï¼®
ï¼°
Ｐ^＋
ï¼®
ï¼®
P substrate
ＧＮＤ
Parasitic diode
Transistor (NPN)
(PinB)
ï¼¢
ï¼£
ï¼¥
(PinA)
Parasitic diode
ï¼®
ＧＮＤ
Ｐ^＋
ï¼°
Ｐ^＋
ＧＮＤ
(PinB)
ï¼®
ï¼®
ï¼®
P substrate
ＢＣ
ＧＮＤ
ï¼¥
Parasitic elementals
Other adiacent components ^{ＧＮＤ} _{Parasitic diode}
●Power Dissipation Reduction
1000
800
※IC mounted on a ROHM standard board
(70mm X 70mm X 1.6mm, glass epoxy)
600
400
200
0
0
25
50
75
100
125
150
175
AMBIENT TEMPERATURE：Ta(℃)
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15/16
2009.05 - Rev.A