l297.pdf

L297/A/D

STEPPER MOTOR CONTROLLERS

NORMAL/WAWE DRIVE

HALF/FULL STEP MODES

CLOCKWISE/ANTICLOCKWISE DIRECTION

SWITCHMODE LOAD CURRENT REGULA-

TION

PROGRAMMABLE LOAD CURRENT

FEW EXTERNAL COMPONENTS

RESET INPUT & HOME OUTPUT

ENABLE INPUT

STEP-PULSE DOUBLER (L297A only)

DIP20

SO20

ORDERING NUMBERS : L297 - L297A (DIP20)

L297D (SO20)

DESCRIPTION

The L297/A/D Stepper Motor Controller IC gener-

ates four phase drive signals for two phase bipolar

and four phase unipolar step motors in microcom-

puter-controlled applications. The motor can be

driven in half step, normal and wawe drive modes

and on-chip PWM chopper circuits permit switch-

mode control of the current in the windings. A

feature of this device is that it requires only clock,

direction and mode input signals. Since the phase

are generated internally the burden on the micro-

processor, and the programmer, is greatly reduced.

Mounted in DIP20 and SO20 packages, the L297

can be used with monolithic bridge drives such as

the L298N or L293E, or with discrete transistors

ABSOLUTE MAXIMUM RATINGS

Symbol

Parameter

Value

Unit

V s

Supply voltage

V i

Input signals

P tot

Total power dissipation (T amb = 70

T stg , T j Storage and junction temperature

-40 to + 150

TWO PHASE BIPOLAR STEPPER MOTOR CONTROL CIRCUIT

October 1995

1/12

L297-L297A-L297D

PIN CONNECTION (L297)

L297

L297D

BLOCK DIAGRAM (L297/L297D)

2/12

L297-L297A-L297D

PIN CONNECTION (L297A)

BLOCK DIAGRAM (L297A)

THERMAL DATA

Symbol

Parameter

DIP20

SO20

Unit

R th-j-amb

Thermal resistance junction-ambient

max

100

C/W

3/12

L297-L297A-L297D

PIN FUNCTIONS - L297/L297D

NAME

FUNCTION

SYNC

Output of the on-chip chopper oscillator.

The SYNC connections The SYNC connections of all L297s to be

synchronized are connected together and the oscillator

components are omitted on all but one. If an external clock

source is used it is injected at this terminal.

GND

Ground connection.

HOME

Open collector output that indicates when the L297 is in its initial

state (ABCD = 0101).

The transistor is open when this signal is active.

Motor phase A drive signal for power stage.

INH1

Active low inhibit control for driver stage of A and B phases.

When a bipolar bridge is used this signal can be used to ensure

fast decay of load current when a winding is de-energized. Also

used by chopper to regulate load current if CONTROL input is low.

Motor phase B drive signal for power stage.

Motor phase C drive signal for power stage.

INH2

Active low inhibit control for drive stages of C and D phases.

Same functions as INH1.

Motor phase D drive signal for power stage.

ENABLE

Chip enable input. When low (inactive) INH1, INH2, A, B, C and D

are brought low.

CONTROL

Control input that defines action of chopper.

When low chopper acts on INH1 and INH2; when high chopper

acts on phase lines ABCD.

V s

5V supply input.

SENS 2

Input for load current sense voltage from power stages of phases

C and D.

SENS 1

Input for load current sense voltage from power stages of phases

A and B.

V ref

Reference voltage for chopper circuit. A voltage applied to this pin

determines the peak load current.

OSC

An RC network (R to V CC , C to ground) connected to this terminal

determines the chopper rate. This terminal is connected to

ground on all but one device in synchronized multi - L297

configurations. f

1/0.69 RC

CW/CCW

Clockwise/counterclockwise direction control input.

Physical direction of motor rotation also depends on connection

of windings.

Synchronized internally therefore direction can be changed at any

time.

CLOCK

Step clock. An active low pulse on this input advances the motor

one increment. The step occurs on the rising edge of this signal.

4/12

L297-L297A-L297D

PIN FUNCTIONS - L297/L297D (continued)

NAME

FUNCTION

HALF/FULL

Half/full step select input. When high selects half step operation,

when low selects full step operation. One-phase-on full step

mode is obtained by selecting FULL when the L297’s translator is

at an even-numbered state.

Two-phase-on full step mode is set by selecting FULL when the

translator is at an odd numbered position. (The home position is

designate state 1).

RESET

Reset input. An active low pulse on this input restores the

translator to the home position (state 1, ABCD = 0101).

PIN FUNCTIONS - L297A

Pin function of the L297A are identical to those of the L297/L297D except for pins 1 and 11.

NAME

FUNCTION

DOUBLER

An RC network connected to this pin determines the delay

between an input clock pulse and the corresponding ghost pulse.

DIR-MEM

Direction Memory. Inverted output of the direction flip flop. Open

collector output.

CIRCUIT OPERATION

The L297(A) is intended for use with a dual bridge

driver, quad darlington array or discrete power de-

vices in step motor driving applications. It receives

step clock, direction and mode signals from the

systems controller (usually a microcomputer chip)

and generates control signals for the power stage.

The principal functions are a translator, which gen-

erates the motor phase sequences, and a dual

PW/M chopper circuit which regulates the current

in the motor windings. The translator generates

three different sequences, selected by the

HALF/FULL input. These are normal (two phases

energised), wave drive (one phase energised) and

half-step (alternately one phase energised/two

phases energised). Two inhibit signals are also

generated by the L297 in half step and wave drive

modes. These signals, which connect directly to the

L298’s enable inputs, are intended to speed current

decay when a winding is de-energised. When the

L297 is used to drive a unipolar motor the chopper

acts on these lines.

An input called CONTROL determines whether the

chopper will act on the phase lines ABCD or the

inhibit lines INH1 and INH2. When the phase lines

are chopped the non-active phase line of each pair

(AB or CD) is activated (rather than interrupting the

line then active). In L297 + L298 configurations this

technique reduces dissipation in the load current

sense resistors.

A common on-chip oscillator drives the dual chop-

per. It supplies pulses at the chopper rate which set

the two flip-flops FF1 and FF2. When the current in

a winding reaches the programmed peak value the

voltage across the sense resistor (connected to one

of the sense inputs SENS 1 or SENS 2 ) equals V ref

and the corresponding comparator resets its flip

flop, interrupting the drive current until the next

oscillator pulse arrives. The peak current for both

windings is programmed by a voltage divider on the

V ref input.

Ground noise problems in multiple configurations

can be avoided by synchronising the chopper oscil-

lators. This is done by connecting all the SYNC pins

together, mounting the oscillator RC network on

one device only and grounding the OSC pin on all

other devices.

The L297A includes a pulse doubler on the step

clock line which is intended to simplify the imple-

mentation of multiple stepping. A ghost pulse is

generated automatically after each input pulse, de-

layed by the time 0.75 R d C d .

The RC network should be dimensioned to place

the ghost pulse roughly halfway between clock

pulses. If pin 1 (DOUBLER) is grounded the doubler

function is disabled.

5/12

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