bd4729g ROHM Co. Ltd., bd4729g Datasheet - Page 4

• Manufacturer Part Number: bd4729g
• Description: Bipolar Voltage Detector Ic
• Manufacturer: ROHM Co. Ltd.

●Explanation of Operation
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Precautions
Please be aware that when there is resistance on the power supply line, the detection voltage varies with voltage drops caused by the IC
current consumption.
Please connect a capacitor between VCC and GND when the power supply line has high impedance.
When the power supply is turned on, the output is unsettled from after over the operating limit voltage (VOPL) until TPHL. There fore it is
possible that the reset signal is not outputted when the rise time of VDD is faster than TPHL.
When VDD is greater than VOPL but less than the reset release voltage (VS + ∆VS), the output voltages will switch to Low.
If VDD exceeds the reset release voltage (VS + ∆VS), then VOUT switches from L to H.
If VDD drops below the detection voltage (VS) when the power supply is powered down or when there is a power supply fluctuation,
VOUT switches to L (with a delay of TPHL).
The potential difference between the detection voltage and the release voltage is known as the hysteresis width (∆VS). The system is
designed such that the output does not flip-flop with power supply fluctuations within this hysteresis width, preventing malfunctions due to
noise.
BD47 □□ G series has the detection voltages and release voltages as threshold voltages and, as the voltages applied to the input reach
their respective threshold voltages, the output switches from “High” to “Low” and from “Low” to “High”. The release voltage has a
hysteresis that is the detection voltage +50mV (Typ.), preventing chattering in the output. When the input is greater than the release
voltage, the output is in a “High” state. When the input is lowered from that state, the output switches to “Low” on the detection voltage.
When the input is less than the detection voltage, the output is in a “Low” state. When the input is raised from that state, the output
switches to “High” with the release voltage. Additionally, at least 0.85V is required for the circuit to operate fully. When the input falls below
the operating limit voltage, the output becomes unsettled.
V
V
DD
OUT
0V
V
V
V
OH
OL
S
+ΔV
V
OPL
V
T
V
DD
PHL
S
S
Fig.11 Timing Waveform
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②
4/8
T
PLH
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T
PHL
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T
PLH
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