PBL 3776/1

8

Figure 10. Stepping modes.

Information given in this data sheet is believed to be

accurate and reliable. However no responsibility is

assumed for the consequences of its use nor for any

infringement of patents or other rights of third parties

which may result from its use. No license is granted

by implication or otherwise under any patent or patent

rights of Ericsson Components. These products are

sold only according to Ericsson Components' general

conditions of sale, unless otherwise confirmed in

writing.

Specifications subject to change without

notice.

1522-PBL 3776/1 Uen Rev. D

© Ericsson Components AB 1999

Ericsson Components AB

SE-164 81 Kista-Stockholm, Sweden

Telephone: +46 8 757 50 00

V

R1

Dis

1

Phase

1

Phase

2

Dis

2

I

MA1

I

MA2

100%

–100%

–100%

100%

Full step mode

Half step mode

Modified half step mode

V

R2

140%

100%

140%

100%

140%

–140%

140%

–140%

is made. The motor will then have taken

two half steps equalling one full step in

rotary movement. The cycle is repeated,

but on the other phase. A total of eight

states are sequenced until the initial state

is reached again.

Half-step mode can overcome poten-

tial resonance problems. Resonances

appear as a sudden loss of torque at one

or more distinct stepping rates and must

be avoided so as not to loose control of

the motor´s shaft position.

One disadvantage with the half-step

mode is the reduced torque in the half

step positions, in which current flows

through one winding only. The torque in

this position is approximately 70 % of the

full step position torque.

Modified half-step mode.The torque

variations in half step mode will be elimi-

nated if the current is increased about

1.4 times in the halfstep position. A

constant torque will further reduce

resonances and mechanical noise,

resulting in better performance, life

expectancy and reliability of the mechani-

cal system.

Modifying the current levels must be

done by bringing the reference voltage

up (or down) from its nominal value

correspondingly. This can be done by

using DACs or simple resistor divider

networks.

See SMD and application handbook

for more information on implementing modified half step.

Ordering Information

Package

Part No.

Plastic DIP Tube

PBL 3776/1NS