THM3561 Datasheet, PDF (12/21 Pages) THine Electronics, Inc. – Stepping Motor Driver with LVDS Interface

THM3561_Rev1.01_E
Functional Description
High-side clamp diode
This device contains clamp diode with high-side of each output driver.
Connect the DIOA pin and DIOB pin (cathode side of clamp diode) to the power supply of the motor in order to
protect the output driver from reverse electricity by the driving of the inductor.
It is also recommended that the condenser of 1uF standard be connected to the VM line near the DIOA/DIOB pin
of the driver, in order to prevent a rise in the clamp voltage due to fluctuations in the power supply of the motor (VM)
due to power supply impedance.
As a configuration of clamp circuit, zener diode or a resistor may also be inserted between the DIOA pin, DIOB
pin and power supply of the motor. In the case of using zener diode, take care that the sum of the motor V_z (zener
voltage) and V_f of clamp diode (forward voltage) does not exceed the recommended operation range of the driver
output pins (OUTA0 to OUTB1 pins) of this product. In the case of using the resistor, V_r that is determined by the
product of motor current and resistance value is added to V_f and the motor voltage, instead of V_z. Take care that this
value does not exceed the recommended operation range of the driver output pins (OUTA0 to OUTB1 pins) of this
product.
Figure 10. Example of High-side Clamp Circuit
[Calculation example] Condition: Motor voltage 12V / motor current 700mA
Vf = 2.5V (typ.)@700mA Hence, 45V (recommended operating voltage) > 12V + 2.5V + Vz.
Therefore, Vz< 30.5 V.
(The zener voltage is sometimes higher than the increase in the current in 2-phase excitation etc.
Depending upon the configuration of the system side circuit. Keep adequate margins at the time of
designing.)
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