STK672-640C-E View Datasheet(PDF) - ON Semiconductor

Part Name

Description

Manufacturer

STK672-640C-E

2-phase Stepping Motor Driver

ON Semiconductor 

STK672-640C-E

ENABLE

Vref

Output current

Constant-current PWM operation must not be performed for 30 µs or less.

<Connection of capacitors between output pins and GND prohibited>

Capacitors must not be connected between the phase A (pin 4), phase AB (pin 5), phase B (pin 3) and phase BB

(pin 1) outputs and GND. What happens if capacitors are connected is that open-circuit detection may be triggered

by the discharge current of the capacitors when the internal MOSFET is set ON. This current is not an inductance

current generated by the motor winding but a capacitor current so a negative current will not flow to the other phase

in each pair of phases, possibly causing the driver to shut down.

<Excessive external noise>

If, when the motor current rises prior to the PWM operation, a spike-shaped current exceeding the Vref-setting

current is generated by excessive external noise, for instance, before the current level (0.7A for the STK672-632C-E

and 630C-E, 1.1A for the STK672-642C-E and 640C-E motor drivers) at which motor pin open-circuiting can be

detected is reached, the internal MOSFET is set OFF.

Since the MOSFET has been set OFF before the actual motor current reaches 0.5A (or 0.8A), the level of the

negative current subsequently flowing to the other phase in each pair of phases is low, and it may be judged that no

negative current is flowing, possibly causing open-circuit detection to be triggered. During normal constant-current

PWM operation, the duration of 5.5μs, which is equivalent to 25% of the initial operation in the PWM period,

corresponds to the section where the current is not detected, and this ensures that no current is detected for the

linking part of the current that is generated in this section. The no-current detection section is not synchronized at

the current rise prior to the PWM operation so when a spike-shaped current exceeding the Vref-setting current is

generated, the MOSFET is set OFF at the stage where the level of the actual motor current is low. As a result, the

level of the negative current subsequently flowing to the other phase in each pair of phases is low, and it may be

judged that no negative current is flowing, possibly causing open-circuit detection to be triggered.

Motor

current

Spike-shaped current

Vref setting

current (IOH)

Current level at

which open-

circuiting is

detected

No-current detection time (5.5μs typ)

PWM period

No. A2116-16/27

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