Block Diagram and Application Circuit

Truth Table

(

): LB1860M, 1861M

IN

+

IN

–

Ct

Rt1

Rt2

CR

OUT1

OUT2

RD

Mode

H

L

H

L

—

L

H

L

L

Full speed

L

H

H

L

—

L

L

H

L

Full speed

(H)

(L)

—

—

(H)

(L)

(H)

(L)

(L)

(Full speed)

(L)

(H)

—

—

(H)

(L)

(L)

(H)

(L)

(Full speed)

—

—

L

H

L

L

H

H

L

Low speed

—————

HHHH

Lock protection

Designer’s Notes

(1) Variable-speed circuit (Rt and Ct pins) — Refer to the application circuit diagram

.

The time constant gained by external components C2 and R2 is used to set the length of an ‘off’ operation time period after

phase switching. This means that the variable-speed operations can be performed by changing the ‘on’ operation time of each

phase through the duty control.

.

The sawtooth waveform signals are generated by the C2-R2 time constant. The voltage of this signal (Ct pin voltage) increases

output circuit is turned off.

.

.

↑↑

Fixed

Rotation speed

constant

proportional constant

Constant

current

circuit

Output timing control

Unit (resistance:

Ω, capacitance: F)

Figure 1

(

): MFP14S

0.47 to 10 µ

LB1860,1860M,1861,1861M

No.3519-3/6