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© 2020 ROHM Co., Ltd. All rights reserved.

BD18326NUF-M

28.Sep.2020 Rev.001

www.rohm.com

TSZ22111 • 15 • 001

TSZ02201-0T1T0B300340-1-2

Operational Notes – continued

10. Regarding the Input Pin of the IC

This monolithic IC contains P+ isolation and P substrate layers between adjacent elements in order to keep them

isolated. P-N junctions are formed at the intersection of the P layers with the N layers of other elements, creating a

parasitic diode or transistor. For example (refer to figure below):

When GND > Pin A and GND > Pin B, the P-N junction operates as a parasitic diode.

When GND > Pin B, 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, operational faults, or physical damage. Therefore, conditions that cause these diodes to

operate, such as applying a voltage lower than the GND voltage to an input pin (and thus to the P substrate) should be

avoided.

Figure 12. Example of Monolithic IC Structure

11. Ceramic Capacitor

When using a ceramic capacitor, determine a capacitance value considering the change of capacitance with

temperature and the decrease in nominal capacitance due to DC bias and others.

12. Thermal Shutdown Circuit (TSD)

This IC has a built-in thermal shutdown circuit that prevents heat damage to the IC. Normal operation should always

be within the IC’s maximum junction temperature rating. If however the rating is exceeded for a continued period, the

junction temperature (Tj) will rise which will activate the TSD circuit that will turn OFF power output pins. When the Tj

falls below the TSD threshold, the circuits are automatically restored to normal operation.

Note that the TSD circuit operates in a situation that exceeds the absolute maximum ratings and therefore, under no

circumstances, should the TSD circuit be used in a set design or for any purpose other than protecting the IC from

heat damage.

13. Functional Safety

“ISO 26262 Process Compliant to Support ASIL-*”

A product that has been developed based on an ISO 26262 design process compliant to the ASIL level described in

the datasheet.

“Safety Mechanism is Implemented to Support Functional Safety (ASIL-*)”

A product that has implemented safety mechanism to meet ASIL level requirements described in the datasheet.

“Functional Safety Supportive Automotive Products”

A product that has been developed for automotive use and is capable of supporting safety analysis with regard to

the functional safety.

Note: “ASIL-*” is stands for the ratings of “ASIL-A”, “-B”, “-C” or “-D” specified by each product's datasheet.

N

N

P

N

N

P Substrate

GND

N P

+

N

N

N P

P Substrate

GND

GND

Parasitic

Elements

Pin A

Pin A

Pin B

Pin B

B

C

E

Parasitic

Elements

GND

Parasitic

Elements

C

B

E

Transistor (NPN)

Resistor

N Region

close-by

Parasitic

Elements