NCV70522MN(2012) 데이터 시트보기 (PDF) - ON Semiconductor

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NCV70522MN
(Rev.:2012)

Micro-Stepping Motor Driver

ON Semiconductor 

NCV70522MN

exist per electrical period, yielding in total 4 zero−current

observation points per electrical period.

ICOIL

VBEMF

t

Previous

Micro−Step

ICOIL

ZOOM

Coil Current Zero Crossing

Current Decay

Zero Current

Next

Micro−Step

t

VCOIL

VBB

Voltage Transient

|VBEMF|

t

Figure 13. Principle of Bemf Measurement

Because of the relatively high re−circulation currents in

the coil during current decay, the coil voltage VCOIL shows

a transient behavior. As this transient is not always desired

in application software, two operating modes can be selected

by means of the bit <SLAT> (see “SLA−transparency” in

Table 12). The SLA pin shows in “transparent mode” full

visibility of the voltage transient behavior. This allows a

sanity−check of the speed−setting versus motor operation

and characteristics and supply voltage levels. If the bit

“SLAT” is cleared, then only the voltage samples at the end

of each coil current zero crossing are visible on the

SLA−pin. Because the transient behavior of the coil voltage

is not visible anymore, this mode generates smoother Back

e.m.f. input for post−processing, e.g. by software.

In order to bring the sampled Back e.m.f. to a descent

output level (0 V to 5 V), the sampled coil voltage VCOIL is

divided by 2 or by 4. This divider is set through a SPI bit

<SLAG>. (See Table 12)

The following drawing illustrates the operation of the

SLA−pin and the transparency−bit. “PWMsh” and

“Icoil=0” are internal signals that define together with SLAT

the sampling and hold moments of the coil voltage.

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