BH6578FVM,BD7931F

Technical Note

7/8

www.rohm.com

2011.05 - Rev.B

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(12) IC terminal input

The present IC is a monolithic IC and has P

With this P layer and N layer of each element, PN junction is formed, and various parasitic elements are formed.

For example, when resistors and transistors are connected to terminals as is the case of Fig.20, where in the case of

resistor, the potential difference satisfies the relation of ground (GND)>(terminal A), and in the case of transistor (NPN),

the potential difference satisfies the relation of ground (GND)>(terminal B), PN junction works as a diode.

Furthermore, in the case of transistor (NPN), a parasitic NPN transistor operates by the N-layer of other elements

adjacent to the parasitic diode.

The parasitic element is inevitably formed because of the IC construction.

The operation of the parasitic element gives rise to mutual interference between circuits and results in malfunction, and

eventually, breakdown. Consequently, take utmost care not to use the IC to operate the parasitic element such as

applying voltage lower than GND (P substrate) to the input terminal.

In addition, when the power supply voltage is not applied to IC, do not apply voltage to the input terminal, either.

Similarly, when the power supply voltage is applied, each input terminals shall be the voltage below the power supply

voltage or within the guaranteed values of electrical properties.

(13) GND wiring pattern

If there are a small signal GND and a high current GND, it is recommended to separate the patterns for the high current

GND and the small signal GND and provide a proper grounding to the reference point of the set not to affect the voltage

at the small signal GND with the change in voltage due to resistance component of pattern wiring and high current. Also for

GND wiring pattern of the component externally connected, pay special attention not to cause undesirable change to it.

Resistor

Transistor(NPN)

N

N

N

P

+

P

+

P

P-sub

GND

Terminal A

N

N

P

+

P

+

P

GND

C

B

E

N

GND

E

B

C

GND

Parasitic element

Fig.20 Example of the basic structure of a bipolar IC

Terminal A

Terminal B

Terminal B

Parasitic element

Parasitic element

Parasitic

element

P-sub