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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.
V
OUT
R2
V
DD
BD48
□□□
BD49
□□□
GND
R1
I1
V1
CIN
I
DD
V
DD
V
DET
0
Through Current
Fig.19 Current Consumption vs. Power Supply Voltage
