BDJ0901HFV-TR Datasheet, PDF (10/17 Pages) Rohm – Temperature Sensor ICs Low current Thermostat Output

BDJxxx1HFV Series
Operational Notes – continued
11. Unused Input Pins
Input pins 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 pins 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.
Resistor
Transistor (NPN)
Pin A
Pin A
Pin B
C
B
E
Pin B
P⁺
N
N
Parasitic
Elements
P
P⁺
N
N
P Substrate
GND
Parasitic
Elements
N ^P+
N _{P N P}⁺ _N
P Substrate
Parasitic
GND GND
Elements
Figure 6. Example of monolithic IC structure
B
N Region
close-by
C
E
Parasitic
Elements
GND
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TSZ22111・15・001
10/13
TSZ02201-0M2M0F515120-1-2
06.Nov.2015 Rev.001