stk672-442b-e Sanyo Semiconductor Corporation, stk672-442b-e Datasheet - Page 13

• Manufacturer Part Number: stk672-442b-e
• Description: 2-phase Stepping Motor Driver
• Manufacturer: Sanyo Semiconductor Corporation

2. STK672-422B-E/432B-E/442B-E/440B-E motor terminal open detection, overcurrent detection, and overheat
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.
[Overcurrent detection]
This hybrid IC is equipped with a function for detecting overcurrent that arises when the motor burns out or when there
is a short between the motor terminals.
Overcurrent detection occurs at 2.3A typ with the STK672-422B-E, 3.4A typ with the STK672-432B-E, and 5.0A typ
with the STK672-442B-E.
Overcurrent detection begins after an interval of no detection (a dead time of 1.25μs typ) during the initial ringing part
during PWM operations. The no detection interval is a period of time where overcurrent is not detected even if the
current exceeds I OH .
[Overheat detection]
Rather than directly detecting the temperature of the semiconductor device, overheat detection detects the temperature
of the aluminum substrate (144°C typ).
Within the allowed operating range recommended in the specification manual, if a heat sink attached for the purpose of
reducing the operating substrate temperature, Tc, comes loose, the semiconductor can operate without breaking.
However, we cannot guarantee operations without breaking in the case of operations other than those recommended,
such as operations at a current exceeding I OH max that occurs before overcurrent detection is activated.
detection functions
[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 voltage difference with the GND potential becomes smaller, making detection
difficult. The motor currents that can be detected by motor terminal open detection are 0.6A or more with the
STK672-422B-E, 0.9A or more with the STK672-432B-E, and 1.1A or more with the STK672-442B-E/440B-E.
Set motor
current,
I OH
Current detection
resistor voltage
0V (GND potential)
MOSFET gate signal
Normal operation
Current when motor terminals are shorted
No detection interval
(1.25 μ s typ)
PWM period
PWM period
STK672-442B-E
Operation when motor pins are shorted
MOSFET all OFF
1.25 μ s typ
Terminal open
Used to set the motor current
Used for open detection
(Negative current does not flow
when the terminal is open.)
Overcurrent detection
I OH max
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