ST L297 User Manual

STEPPER MOT OR CONTROLLERS

NORMAL/WAVE DRIVE HALF/FULL STEP MODES CLOCKWISE/ANTICLOCKWISE DIRECTION SWITCHMODE LOAD CURRENT REGULA-

TION PROGRAMMA BLE LO A D CURRE NT FEW EXTERNAL COMPONENTS RESET INPUT & HOME OUTPUT ENABLE INPUT

DIP20 SO20

ORDERING NUMBERS

L297D (SO20)

: L297/1 (DIP20)

L297

DESCRIPTION

The L297 Stepper Motor Controller I C generates four phase drive signals for two phase bipolar and four phase unipolar step motors in m icrocomputercontrolled applications. The motor can be driven in half step, normal and wawe drive modes and onchip 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 microprocessor, 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 and darlingtons.

ABSOL UT E MAXIMUM R ATINGS

Symbol Parameter Value Unit

stg

Supply voltage 10 V

Input signals 7V

Total power dissipation (T

tot

, TjStorage and junction temperature -40 to + 150

amb

= 70°C)

TWO PHASE BIPOLAR STEP PE R MOTOR CONTROL CIRCUIT

December 2001

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L297

PIN CONNECTION

BLOCK DIA GRAM

(Top view)

L297/1 L297D

(L297/1 - L297D)

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PIN FUNCTIONS - L297/1 - L297D

L297

NAME FUNCTION

1 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. 2 GND Ground connection. 3 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. 4 A Motor phase A drive signal for power stage. 5

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. 6 B Motor phase B drive signal for power stage. 7 C Motor phase C drive signal for power stage. 8

INH2 Active low inhibit control for drive stages of C and D phases.

Same functions as INH1. 9 D Motor phase D drive signal for power stage.

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

are brought low.

11 CONTROL Control input that defines action of chopper.

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

acts on phase lines ABCD.

12 V

13 SENS

5V supply input.

Input for load current sense voltage from power stages of phases

C and D.

14 SENS

Input for load current sense voltage from power stages of phases

A and B.

15 V

ref

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

determines the peak load current.

16 OSC

An RC network (R to V

determines the chopper rate. This terminal is connected to ground

, C to ground) connected to this terminal

on all but one device in synchronized multi - L297 configurations. f

1/0.69 RC

≅

17 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.

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L297

PIN FUNCTIONS - L297/1 - L297D

19 HALF/

NAME FUNCTION

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

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

(continued)

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).

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

THERMAL DATA

Symbol Parameter DIP20 SO20 Unit

th-j-amb

CIRCUIT OPERATION

The L297 is intended for use with a dual brid ge driver, quad darlington array or discrete power devices in step motor driving applications. It re-

Thermal resistance junction-ambient max 80 100

are chopped the non-active phase line of eac h 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.

ceives step cloc k , direction and m ode signals from the systems controller (usually a microcomputer chip) and generates control signals for the power stage.

The principal functions are a translator, whic h generates the motor phase sequences, and a dual PWM chopper circuit which regulates the current in the motor windings. The t ranslator 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 wa ve drive modes. These signals, which connect directly to the L298’s enable inputs, are intended to speed c ur rent dec ay 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 CONTR OL determines whether the

A common on-chip oscillator drives the dual chopper. It supplies pulses at the chopper rate which set the two flip-flops FF1 and FF2. When the current in a winding reaches the pr ogrammed peak v alue the voltage across the sense resistor (connected to one of the sense inputs SENS

and the corresponding comparator resets its

ref

or SENS2) equals

flip flop, interrupting the drive current until the next oscillator pulse arrives. The peak current for both windings is programmed by a v oltage divider on the

input.

ref

Ground noise problems in multiple configurations can be avoided by synchronising the chopper oscillators. 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. chopper will act on the phase lines ABCD or the inhibit lines INH1 and INH2. When the phase lines

C/W

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