Technical Note

7/9

BD48

□□G, BD48□□FVE, BD49□□G, BD49□□FVE series

www.rohm.com

2009.04 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

Examples of the power supply with resistor dividers

In applications where the power supply input terminal (VDD) of an IC with resistor dividers, it is possible that a through

current will momentarily flow into the circuit when the output logic switches, resulting in malfunctions (such as output

oscillatory state).

(Through-current is a current that momentarily flows from the power supply (VDD) to ground (GND) when the output level

switches from “High” to “Low” or vice versa.)

Fig.18

A voltage drop of [the through-current (I1)] × [input resistor (R2)] is caused by the through current, and the input voltage to

descends, when the output switches from “Low” to “High”. When the input voltage decreases and falls below the detection

voltage, the output voltage switches from “High” to “Low”. At this time, the through-current stops flowing through output

“Low”, and the voltage drop is eliminated. As a result, the output switches from “Low” to “High”, which again causes the

through current to flow and the voltage drop. This process is repeated, resulting in oscillation.

R2

BD48□□□

BD49□□□

GND

R1

I1

V1

CIN

0

Through Current

Fig.19 Current Consumption vs. Power Supply Voltage