lv8735v ON Semiconductor, lv8735v Datasheet - Page 11

• Manufacturer Part Number: lv8735v
• Description: Bi-cmos Lsi Pwm Constant-current Control Stepping Motor Driver
• Manufacturer: ON Semiconductor

(4) Setting constant-current control reference current
(5) Input timing
(6) Blanking period
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 :
* 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
The formula used to calculate the output current when using the function for attenuating the VREF input voltage is
given below.
Example : At VREF of 1.5V, a reference voltage setting of 100% [(ATT1, ATT2) = (L, L)] and an RF resistance of
If, when exercising PWM constant-current chopping control over the motor current, the mode is switched from decay
to charge, the recovery current of the parasitic diode may flow to the current sensing resistance, causing noise to be
carried on the current sensing resistance pin, and this may result in erroneous detection. To prevent this erroneous
detection, a blanking period is provided to prevent the noise occurring during mode switching from being received.
During this period, the mode is not switched from charge to decay even if noise is carried on the current sensing
resistance pin.
In the stepping motor driver mode (DM = Low or Open) of this IC, the blanking time is fixed at approximately 1μs.
In the DC motor driver mode (DM = High), the blanking time can be switched to one of two levels using the
RST/BLK pin. (Refer to "Blanking time switching function.")
STEP
MD1
MD2
FR
ATT1
High
High
Low
Low
I OUT = (VREF/5)/RF resistance
0.5Ω, the output current is set as shown below.
If, in this state, (ATT1, ATT2) is set to (H, H), IOUT will be as follows :
In this way, the output current is attenuated when the motor holding current is supplied so that power can
be conserved.
I OUT = (VREF/5) × (attenuation ratio)/RF resistance
I OUT = 1.5V/5 × 100%/0.5Ω = 0.6A
I OUT = 0.6A × 20% = 120mA
ATT2
High
High
Low
Low
TstepH TstepL
Current setting reference voltage attenuation ratio
(md1 step)
Tds
TstepH/TstepL : Clock H/L pulse width (min 500ns)
LV8735V
(step md1)
100%
80%
50%
20%
Tdh
Tds : Data set-up time (min 500ns)
Tdh : Data hold time (min 500ns)
(md2 step)
Tds
(step md2)
Tdh
(fr step)
Tds
(step fr)
Tdh
No.A1848-11/26