STK672-010 Просмотр технического описания (PDF) - SANYO -> Panasonic

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STK672-010

Unipolar Fixed-Current Chopper (separate excitation) Type 1.7 A Output Current Stepping Motor Driver with Built-in 4-Phase Distribution Controller

SANYO -> Panasonic 

STK672-010

<Output Current Setting>

Figure 8 shows the motor output current waveform.

The output current IOH is set by the STK672-010 pin 4 (5) voltage.

The formulas for these calculations are as follows.

Vref =

RO2

RO1 + RO2

× VCC2 .................................................. (2)

IOH = K ×

Vref

RS

.................................................................... (3)

RS: The hybrid IC internal current detection resistor

(0.33 ± 3%)

K: 1.1 to 1.2 (correction coefficient for differences

between settings and measurements)

Fig. 8 Motor Output Current Waveform

K is a proportionality constant that corrects for discrepancies between

measurements and settings. Since the value of K is the set value in one

condition, the value must be reset for each condition examined.

Sources of error include motor supply voltage and the motor electrical

characteristics.

Fig. 9: Vref Peripheral Circuit

The output current range is from 0.1 A of the current caused by the tOFF time in oscillator to 1.7 A of the allowable

maximum current.

<Notes on W1-2 Phase Excitation Current Switching>

The STK672-010 provides the control logic circuit to allow the current to be switched over up to four levels by the C1,

C2, and C3. A low saturation transistor must be used on the Vref voltage switching device in the W1-2 phase excitation

circuit.

The reason for this is that when the W1-2 phase excitation current is switched over up to four levels, for switching IO at

small settings the IO waveform will be displaced from the desired value due to variations in the VCE (sat) voltage drop of

the external Vref switching device. This can result in increased motor vibrations. Therefore we recommend selecting a

device with a VCE (sat) of about 10 mV at IC = 100 µA for this transistor at the operating conditions used for this circuit.

Note that although we proposed using the LB1212 or LB1214, this does not necessarily apply to designs that take mass

production into consideration.

The output current setting ratios for W1-2 phase excitation are 100%, 92%, 70%, and 38% for four-level switching and

100% and 70% for two-level switching. These are target values and precise adjustment should be made in the actual

circuit.

A description of the W1-2 phase excitation follows.

No. 4927-9/17

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