PBL 3775/1
Half-step mode. In the half-step mode,
the current in one winding is brought to
zero before a complete current reversal
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.
Thermal resistance [°C/W]
80
70
60
50
40
30
20
16-pin
DIP
20-pin
SO
Half-step mode can overcome
potential resonance problems. Resonan-
ces 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
5
10
15
20
25
30
35
PCB copper foil area [cm2]
PLCC package
DIP package
28-pin
PLCC
Figure 14. Typical thermal resistance vs. PC Board copper area and suggested layout. mode is the reduced torque in the half
step positions, in which current flows
through one winding only. The torque in
Phase1
this position is approximately 70 % of the
full step position torque.
Dis 1
Modified half-step mode.The torque
variations in half step mode will be elimi-
Phase2
nated if the current is increased about
1.4 times in the halfstep position. A
Dis 2
constant torque will further reduce
VR1
resonances and mechanical noise,
140%
100%
resulting in better performance, life
expectancy and reliability of the mecha-
nical system.
VR2
140%
100%
Modifying the current levels must be
done by bringing the reference voltage
IMA1
140%
100%
up (or down) from its nominal value
correspondingly. This can be done by
using DACs or simple resistor divider
–100%
–140%
networks. The PBL 3775/1 is designed
IMA2
140%
to handle about 1.4 times higher current
100%
in one channel on mode, for example 2
x 500 mA in the full-step position, and 1
x 700 mA in the half-step position.
–100%
–140%
Full step mode
Half step mode
Modified half step mode
Figure 15. Stepping modes.
Ordering Information
Package
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.
Part No.
DIP Tube
PLCC Tube
PLCC Tape & Reel
SO Tube
SO Tape & Reel
PBL 3775/1NS
PBL 3775/1QNS
PBL 3775/1QNT
PBL 3775/1SOS
PBL 3775/1SOT
Specifications subject to change without notice.
1522-PBL 3775/1 Uen Rev. F
© Ericsson Components AB 1999
Ericsson Components AB
SE-164 81 Kista-Stockholm, Sweden
Telephone: +46 8 757 50 00
8
ERICSSON [ ERICSSON ]
