LB1841 datasheet(4/7 Pages) SANYO

4 / 7 page

LB1841V

No. 4384-4/7

Sample Application Timing Chart

• Sample Application timing chart

1 Connect DC motor (RL = RΩ) between OUT1 and OUT2, and input forward signal (IN1 = High, IN2 = Low)

with RD pin in pull-up state.

Because output is saturated during startup, set DEL input to Low.

2 DC motor starts and startup current (IST = VM/R) flows through motor.

3 DC motor rotates in normal condition. At this point, set DEL input to High.

4 When DC motor locks up, motor current IM increases. When it reaches Ilimit (=VLIR/(10 Rf)), output current

limiting circuit operates. At the same time, the set current detection circuit sets RD output to Low.

• Reference voltage Vref

The Vref output is linked to the input. When IN1 or IN2 is High, the reference voltage is output.

• Output current limiter circuitry

The circuit configuration is as shown in the separate diagram.

The output set current is determined by the reference voltage VLIR applied to the LIR pin. When VLIR is

applied, 1/10 of the voltage occurs across RS in the diagram. This voltage is input to the + side of the voltage

setting amplifier.

The motor current IM generates a voltage (IM × Rf) across the external resistor Rf. This voltage is input to

the – side of the amplifier. The differential amplifier operates so as to make the two inputs equal, then the

output transistor is driven.

The set current is determined by the following equation:

Ilimit = VLIR/(10Rf) [A]

V(V)

IN1

IN2

DEL

OUT1

OUT2

t (s)

VLIR

10Rf

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