stk672-640b-e Sanyo Semiconductor Corporation, stk672-640b-e Datasheet - Page 13

• Manufacturer Part Number: stk672-640b-e
• Description: 2-phase Stepping Motor Driver
• Manufacturer: Sanyo Semiconductor Corporation

<FAULT1, FAULT2 output>
2. STK672-632B-E/630B-E/642B-E/640B-E overcurrent detection, overheat detection, and motor terminal open
FAULT1 Output
FAULT2 output
detection functions
Each detection function operates using a latch system and turns output off. Because a RESET signal is required to
restore output operations, once the power supply, V DD , is turned off, you must either again apply power on reset
with V DD ON or apply a RESETB=High→Low→High signal.
[Motor terminal open detection]
This hybrid IC is equipped with a function for detecting open output terminals to prevent thermal destruction of the
MOSFET due to repeated avalanche operation that occurs when an output terminal connected to the motor is open.
The open condition is determined by checking the presence or absence of the flyback current that flows in the motor
inductance during the off period of the PWM cycle.
Detection is performed by using the fact that the flyback current does not flow when a motor terminal is open.
When the current level drops, the difference with the GND potential decreases, making detection difficult. The motor
current that can be detected by motor terminal open detection is 0.5A or more with the STK672-632B-E/630B-E and
0.8A or more with the STK672-642B-E/640B-E.
<Notes on the ENABLE high edge>
When ENABLE changes from low to high and the STK672-6XXB-E performs constant-current PWM operation that
flows a negative current during the 30μs period after the high edge, open detection may activate and stop the driver.
The motor current setting voltage Vref must be set so that PWM operation is not performed within a period of 30μs
after the high edge.
If the motor current setup voltage is set for the rated motor current, PWM operation is not performed during this 30μs
period after the high edge, so this is not a problem.
In addition, there is no problem with operation that lowers the current setting Vref after the motor rated current is
reached as shown in the diagram on the following page.
Whether constant-current PWM operation is performed during the 30μs period after the high edge can be judged by
substituting the motor L and R values into the formula on the following page.
Output is resistance divided (3 levels) and the type of abnormality detected is converted to the corresponding output
voltage.
Abnormality detection can be released by a RESETB operation or turning V DD voltage on/off.
FAULT1 is an open drain output. It outputs low level when any of motor terminal open, overcurrent, or overheat is
detected.
• Motor terminal open: 10mV (typ)
• Overcurrent: 2.5V (typ)
• Overheat: 3.3V (typ)
Current detection
resistor voltage
0V (GND potential)
MOSFET gate signal
PWM period
STK672-640B-E
Terminal open
Used to set the motor current
Used for open detection
(Negative current does not flow
when the terminal is open.)
No. A1739-13/24