Data Sheet

16/19
TSZ02201-0M3M0F616080-1-2
© 2014 ROHM Co., Ltd. All rights reserved.
23.May.2016 Rev.002
www.rohm.com
TSZ22111・15・001
BH1745NUC
Operational Notes – continued
11. Unused Input Terminals
Input terminals of an IC are often connected to the gate of a MOS transistor. The gate has extremely high impedance
and extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it. The small
charge acquired in this way is enough to produce a significant effect on the conduction through the transistor and
cause unexpected operation of the IC. So unless otherwise specified, unused input terminals should be connected to
the power supply or ground line.
12. 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 xx. Example of monolithic IC structure
13. Ceramic Capacitor
When using a ceramic capacitor, determine the dielectric constant considering the change of capacitance with
temperature and the decrease in nominal capacitance due to DC bias and others.
14. Area of Safe Operation (ASO)
Operate the IC such that the output voltage, output current, and power dissipation are all within the Area of Safe
Operation (ASO).
N
N
P
+
P
N
N
P
+
P Substrate
GND
N
P
+
N
N
P
+
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