33977 View Datasheet(PDF) - Freescale Semiconductor

Part Name

Description

Manufacturer

33977

Single Gauge Driver

Freescale Semiconductor 

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

STATE MACHINE OPERATION

The 33977 is ideal for use in instrumentation systems

requiring distributed and flexible stepper motor gauge driving.

The device also eases the transition to stepper motors from

air core motors by emulating the air core pointer movement

with little additional processor bandwidth utilization. The two-

phase stepper motor has maximum allowable velocities and

acceleration and deceleration. The purpose of the stepper

motor state machine is to drive the motor with the maximum

performance while remaining within the motor’s voltage,

velocity, and acceleration constraints.

A requirement of the state machine is to ensure the

deceleration phase begins at the correct time and pointer

position. When commanded, the motor [will deleted PV]

accelerates constantly to the maximum velocity, and then it

moves toward the commanded position at the maximum

velocity. Eventually, the pointer reaches the calculated

location where the movement has to decelerate, safely

slowing to a stop at the desired position. During the

deceleration phase, the motor does [will deleted PV] not

exceed the maximum deceleration.

During normal operation, both stepper motor rotors are

microstepped at 24 steps per electrical revolution, illustrated

in Figure 7. A complete electrical revolution results in two

degrees of pointer movement. There is a second smaller

[parentheses removed-unnecessary] state machine in the IC

controlling these microsteps. The smaller state machine

receives clockwise or counter-clockwise index commands at

timed intervals, thereby stepping the motor in the appropriate

direction by adjusting the current in each coil. Normalized

values are provided in Table 5.

Figure 7. Clockwise Microsteps

Table 5. Coil Step Value

Step

Angle

SINE

(Angle)*

0 0.0

0.0

1 15 0.259

2 30

0.5

3 45 0.707

4 60 0.866

5 75 0.966

6 90

1.0

7 105 0.966

8 120 0.866

9 135 0.707

10 150

0.5

COS (Angle -30)*

PE6=0

1.0

0.965

0.866

0.707

0.5

0.259

0.0

-0.259

-0.5

-0.707

-0.866

COS (Angle -30)*

PE6=1

0.866

0.966

1.0

0.966

0.866

0.707

0.500

0.259

0.0

-0.259

-0.500

33977

12

Analog Integrated Circuit Device Data

Freescale Semiconductor

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