MC3479 View Datasheet(PDF) - ON Semiconductor

Part Name

Description

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MC3479

Stepper Motor Driver

ON Semiconductor 

MC3479

Full/Half Step

When this input is at a Logic “0” (<0.8 V), the outputs

change a full step with each clock cycle, with the sequence

direction depending on the CW/CCW input. There are four

steps (Phase A, B, C, D) for each complete cycle of the

sequencing logic. Current flows through both motor coils

during each step, as shown in Figure 7.

When taken to a Logic “1” (>2.0 V), the outputs change

a half step with each clock cycle, with the sequence direction

depending on the CW/CCW input. Eight steps (Phase A to

H) result for each complete cycle of the sequencing logic.

Phase A, C, E and G correspond (in polarity) to Phase A, B,

C, and D, respectively, of the full step sequence. Phase B, D,

F and H provide current to one motor coil, while

de–energizing the other coil. The condition of the outputs of

the de–energized coil depends on the OIC input, see Figure 7

timing diagram.

OIC

The output impedance control input determines the output

impedance to the de–energized coil when operating in the

half–step mode. When the outputs are in Phase B, D, F or H

(Figure 7) and this input is at a Logic “0” (<0.8 V), the two

outputs to the de–energized coil are in a high impedance

condition — QL and QH of both outputs (Figure 5) are off.

When this input is at a Logic “1” (>2.0 V), a low impedance

output is provided to the de–energized coil as both outputs

have QH on (QL off). To complete the low impedance path

requires connecting VD to VM as described elsewhere in this

data sheet.

Bias/Set

This pin can be used for three functions: a) determining

the maximum output sink current; b) setting the internal

logic to a known state; and c) reducing power consumption.

a) The maximum output sink current is determined by the

base drive current supplied to the lower transistors (QLs of

Figure 5) of each output, which in turn, is a function of IBS.

The appropriate value of IBS is determined by:

IBS = IOD x 0.86

where IBS is in microamps, and IOD is the motor current/coil

in milliamps.

Clk

Bias/Set

CW/CCW

Phase A B

L1

L2

L3

L4

Phase A

Output

CDA B

(a) Full Step Mode

CB ADCB

= High Impedance

F/HS

= Logic 0"

OIC

= Don′t Care

AB C D E F G H A B C D

L1

L2

L3

L4

(b) Half Step Mode

CW/CCW

F/HS

= High Impedance

= Logic 0"

= Logic 1", OIC = Logic 0"

L1

L2

L3

L4

Phase A

Output

AB C D E F G H A B C D

(c) Half Step Mode

Figure 7. Output Sequence

http://onsemi.com

6

CW/CCW = Logic 0"

F/HS = Logic 1"

OIC

= Logic 1"

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