LB1843V データシートの表示（PDF） - ON Semiconductor
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LB1843V
ON Semiconductor
LB1843V Datasheet PDF : 10 Pages
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LB1843V
Reference voltage (Vref)
The Vref output is linked to the input; if either IN1 or IN2 is high, the reference voltage is output.
Output current limiter
The schematic for the output current limiter is shown below.
The output set current is set according to the reference voltage VLIR applied to the LIR pin. When VLIR is applied, 1/10
of that voltage is generated at both ends of RS in the diagram; this voltage is input on the positive (+) side of the current
setting amplifier.
The motor current IM generates voltage equal to (IM ´ Rf) at both ends of the external resistor Rf. This voltage is input to
the negative (–) side of the same amplifier, and the differential amplifier functions and the output transistors are driven so
that these inputs become equal.
The set current value in this instance is determined by the following equation:
Ilimit = VLIR/(10Rf) [A]
Set current detector
(1) When DEL = high
If the motor current IM has not reached the set current Ilimit, the input voltage on the negative (–) side of the
amplifier is greater than the input voltage on the positive (+) side. As a result, the drive current increases and the
output PNP transistors reach the saturation state. If this state is detected, the detection signal is sent to the set current
detector, and the RD output goes high.
If the motor current IM reaches the set current Ilimit, the output PNP transistor enters the controlled state, and the RD
output goes low.
(2) When DEL = low
Because the operation of the current setting amplifier is cancelled when a low signal is input to the DEL pin, the
output PNP transistors reach the saturation state and the RD output goes high, just as in the case described above.
The following table summarizes the states described above.
DEL
OUT output
RD
Limit
L
H
Non-limit
Off
L
Saturated
Off
Output Current Limiter and Set Current Detector Block Diagram
No.4385-8/10
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