AN4158 datasheet(7/34 Pages) STMICROELECTRONICS

Part #	AN4158

Description	Peak current control with automatic decay adjustment

PDF	34 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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DocID023635 Rev 2

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AN4158

Stepper motor basics

1.1

Full step and half step

The driving sequence described in the previous section is called full step one phase on (or

wave driving) because the rotor is moved by one step at a time feeding only one of the two

phases of the motor at a time.

It is also possible to drive both the phases in order to generate a magnetic field positioned

halfway between the two phases (1a, 2a, 3a and 4a positions in Figure 3). This driving

mode is called full step two-phase on (or normal driving). In this case, at the same phase

current, the magnetic field is higher by a factor of

2 and the corresponding motor torque is

multiplied by the same factor.

Figure 2. Torque during a step change

Stat

HOLD

Rotor

Mot

Load

MAX

At the step change the displacement

angle is about 90° and the maximum

torque is applied

The rotor approaches

the target step position

and stops when Tmot

is equal to TLoad

AM15104v1

AN4158 Datasheet(PDF) 7 Page - STMicroelectronics