BD4940G-TR Datasheet, PDF (14/18 Pages) Rohm – Standard CMOS Voltage Detector IC

BD48xxx series BD49xxx series
Datasheet
3) 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
BD48xxx
BD49xxx
GND
VOUT
CL
Fig.18
When an in-rush current (I1) flows into the circuit (Refer to Fig. 18) 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
Through Current
0
VDET
VDD
Fig.19 Current Consumption vs. Power Supply Voltage
www.rohm.com
© 2013 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
14/15
TSZ02201-0R7R0G300030-1-2
22.May.2013.Rev.008