LV8731V
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12
Position Detection Monitoring Function
The MONI position detection monitoring pin is of an open
drain type. When the excitation position is in the initial
position, the MONI output is placed in the ON state. (Refer
to “Examples of Current Waveforms in each Micro−step
Mode”)
Setting Constant−Current Control Reference Current
This IC is designed to automatically exercise PWM
constant−current chopping control for the motor current by
setting the output current. Based on the voltage input to the
VREF pin and the resistance connected between RF and
GND, the output current that is subject to the
constant−current control is set using the calculation formula
below :
I
OUT
+
ǒ
VREF
5
Ǔ
ń RF resistance
(eq. 1)
* The above setting is the output current at 100% of each
excitation mode.
The voltage input to the VREF pin can be switched to
four−step settings depending on the statuses of the two
inputs, ATT1 and ATT2. This is effective for reducing power
consumption when motor holding current is supplied.
ATTENUATION FUNCTION FOR VREF INPUT VOLTAGE
ATT1 ATT2 Current Setting Reference Voltage Attenuation Ratio
Low Low 100%
High Low 80%
Low High 50%
High High 20%
The formula used to calculate the output current when
using the function for attenuating the VREF input voltage is
given below.
I
OUT
+
ǒ
VREF
5
Ǔ
(attenuationration) ń RF resistance
(eq. 2)
Example: At VREF of 1.5 V, a reference voltage setting
of 100% [(ATT1, ATT2) = (L, L)] and an RF resistance of
0.3 Ω, the output current is set as shown below.
I
OUT
= 1.5 V / 5 × 100% / 0.3 = 1.0 A
If, in this state, (ATT1, ATT2) is set to (H, H), IOUT will
be as follows :
I
OUT
+ 1.0 A 20% + 200 mA
In this way, the output current is attenuated when the
motor holding current is supplied so that power can be
conserved.
Input Timing
Figure 6. Input Timing
TstepH TstepL
Tds
(md1→step)
Tdh
(step→md1)
Tdh
(step→md2)
Tds
(md2→step)
Tds
(fr→step)
Tdh
(step→fr)
STEP
MD1
MD2
FR
TstepH/TstepL: Clock H/L pulse width (min 500 ns)
Tds: Data set−up time (min 500 ns)
Tdh: Data hold time (min 500 ns)
