LB1836M

No.3947-4/6

Design Notes

If large current flows on the power supply (VS) line and the GND line, then in some applications and layouts,

misoperation due to line oscillation may result.

The modes during which large current flows are as follows :

• Motor surge current when the DC motor starts up or when it shifts rotation directions (forward ↔ reverse).

• Passthrough current generated within the IC when shifting rotation directions (forward ↔ reverse) or when shifting

from forward/reverse rotation to braking, or vice versa.

The following points should be kept in mind regarding the pattern layout :

• Keep the wiring lines thick and short in order to reduce wiring inductance between the power supply (VS) and GND.

• Insert a passthrough capacitor near the IC. (Maximum effect is obtained by inserting the passthrough capacitor

between VS and the pin 7 GND at the closest distance possible.

• If the CPU and the LB1836M are mounted on separate boards and the difference between the ground potential of each

board is large, install resistors of about 10k

Ω in series between the CPU and the LB1836M inputs.

Vcont pin

ID =

VZ

r

(= constant)

As shown in the above diagram, the Vcont pin outputs the voltage of the band gap Zener VZ + VF (=1.93V).

In normal use, this pin is left open.

The drive current ID is varied by the Vcont voltage. However, because the band gap Zener is shared, it functions as a

bridge.

M

OUT

OUT

ID

IN

VCC

Vcont

VZ

VS