AMIS-30521 AMI Semiconductor, Inc., AMIS-30521 Datasheet - Page 13

• Manufacturer Part Number: AMIS-30521
• Description: Micro-stepping Motor Driver
• Manufacturer: AMI Semiconductor, Inc.

AMIS-30521 Micro-stepping Motor Driver
Symbol
V
V
R
C
G
8.4 Programmable Peak-Current
The amplitude of the current waveform in the motor coils (coil peak current = Imax) is adjusted by means of an SPI parameter
"CUR[4:0]"
the next PWM period. More information can be found in
8.5 Speed and Load Angle Output
The SLA-pin provides an output voltage that indicates the level of the Back-e.m.f. voltage of the motor. This Back-e.m.f. voltage is
sampled during every so-called "coil current zero crossings". Per coil, two zero-current positions exist per electrical period, yielding in
total four zero-current observation points per electrical period.
Because of the relatively high recirculation currents in the coil during current decay, the coil voltage V
As this transient is not always desired in application software, two operating modes can be selected by means of the bit <SLAT> (see
"SLA-transparency" in
behavior. This allows a sanity-check of the speed-setting versus motor operation and characteristics and supply voltage levels. If the bit
“SLAT” is cleared, then only the voltage samples at the end of each coil current zero crossing are visible on the SLA-pin. Because the
transient behavior of the coil voltage is not visible anymore, this mode generates smoother Back e.m.f. input for post-processing, e.g.
by software.
In order to bring the sampled Back e.m.f. to a descent output level (0 to 5V), the sampled coil voltage V
divider is set through an SPI bit <SLAG>.
Table 12: Parameter Table SLA Pin
out
off
out
load
sla
AMI Semiconductor – June 2007, M-20683-001
www.amis.com
(Table 13: SPI Control Register
Pin(s)
SLA
Parameter
Output voltage range
Output offset the SLA pin
Output resistance SLA pin
Load capacitance SLA pin
Gain of SLA pin = V
Table 15: SPI Control Register
V
I
COIL
COIL
V
BB
Micro-step
Previous
BEMF
(Table 15: SPI Control Register
/ V
0). Whenever this parameter is changed, the coil-currents will be updated immediately at
COIL
I
COIL
Figure 12: Principle of Bemf Measurement
Coil Current Zero Crossing
Current Decay
2). The SLA pin shows in "transparent mode" full visibility of the voltage transient
Table 24: SPI Control Parameter Overview
Remark/Test Conditions
0.2V < Vsla < Vdd - 0,2V
SLAG=0
SLAG=1
ZOOM
Voltage Transient
Zero Current
13
V
BEMF
2)
Micro-step
V
BEMF
Next
t
t
t
Min.
-20
0.5
PC20070604.7
CUR[4:0].
COIL
COIL
Typ.
0,25
shows a transient behavior.
is divided by 2 or by 4. This
0,5
Data Sheet
Max.
4.5
20
50
1
Unit
mV
kΩ
pF
V