BU45K232G-TL Datasheet, PDF (11/17 Pages) Rohm – Counter Timer Built-in CMOS Voltage Detector IC

BU45Kxxxx, BU46Kxxxx, BU45Lxxxx, BU46Lxxxx series
Datasheet
Examples of the power supply with resistor dividers.
In applications wherein the power supply voltage of an IC comes from a resistor divider circuit, an in-rush current will flow
into the circuit when the output level switches from “High” to “Low” or vice versa. In-rush current is a sudden surge of
current that flows from the power supply (VDD) to ground (GND) as the output logic changes its state. This current flow
may cause malfunction in the systems operation such as output oscillations, etc.
V1
R2
I1
VDD
R1
CIN
BU45xxxxx
BU46xxxxx
GND
VOUT
CL
Fig. 19
When an in-rush current (I1) flows into the circuit (Refer to Fig. 19) at the time when output switches from “Low” to “High”,
a voltage drop of I1×R2 (input resistor) will occur in the circuit causing the VDD supply voltage to decrease. When the VDD
voltage drops below the detection voltage, the output will switch from “High” to “Low”. While the output voltage is at “Low”
condition, in-rush current will stop flowing and the voltage drop will be reduced. As a result, the output voltage will switches
again from “Low” to “High” which causes an in-rush current and a voltage drop. This operation repeats and will result to
oscillation.
IDD
In-rush Current
0
VDET
VDD
Fig. 20 Current Consumption vs. Power Supply Voltage
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