E-TEA3717DP View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

E-TEA3717DP

STEPPER MOTOR DRIVER

STMicroelectronics 

TEA3717

FUNCTIONAL DESCRIPTION

The circuit is intented to drive a bipolar constant cur-

rent through one motor winding. The constant cur-

rent is generated through switch mode regulation.

There is a choice of three different current levels with

the two logic inputs l0 and l1. The current can also

be switched off completely.

other comparator input, the comparator output goes

high, which triggers the pulse generator and its out-

put goes high during a fixed pulse time (toff), thus

switching off the power feed to the motor winding,

and causing the motor current to decrease during

toff.

SINGLE-PULSE GENERATOR

INPUT LOGIC

The pulse generator is a monostable triggered on

the positive going edge of the comparator output.

If any of the logic inputs is left open, the circuit will The monostable output is high during the pulse time,

treat it as a high level input.

toff, which is determined by the timing components

I0

I1

Current Level

H

H No Current

L

H Low Current

H

L Medium Current

Rt and Ct.

toff = 0.69 ⋅R t Ct

The single pulse switches off the power feed to the

motor winding, causing the winding current to de-

L

L Maximum Current

) PHASE − This input determines the direction of cur-

t(s rent flow in the winding, depending on the motor

c connections. The signal is fed through a Schmidt-

u trigger for noise immunity, and through a time delay

d in order to guarantee that no short-circuit occurs in

ro the output stage during phase-shift. High level on

the PHASE-input causes the motor current flow

P from MA through the winding to MB.

te l0 and l1 − The current level in the motor winding is

le selected with these inputs. The values of the differ-

o ent current levels are determined by the reference

s voltage VR together with the value of the sensing re-

b sistor RS.

) - O CURRENT SENSOR

t(s This part contains a current sensing resistor (RS), a

c low pass filter (RC, CC) and three comparators. Only

u one comparator is active at a time. It is activated by

d the input logic according to the current level chosen

ro with signals l0 and l1. The motor current flows

P through the sensing resistor RS. When the current

te has increased so that the voltage across RS be-

comes higher than the reference voltage on the

ole Note : RS = 1 Ω, inductance free

sRC = 1 kΩ

b CC = 820 pF, ceramic

O Rt = 56 kΩ

crease during toff.

If a new trigger signal should occur during toff, it is

ignored.

OUTPUT STAGE

The output stage contains four Darlington transis-

tors and four diodes, connected in an H-bridge. The

two sinking transistors are used to switch the pow-

ersupplied to the motor winding, thus driving a con-

stant current through the winding.

It should be noted however, that it is not permitted

to short circuit the outputs.

VCC, Vmm, VR

The circuit will stand any order of turn-on or turn-off

of the supply voltages VSS and VS. Normal dV/dt

values are then assumed.

Preferably, VR should be tracking VCC during power-

on and power-off.

ANALOG CONTROL

The current levels can be varied continuously either

if VR is varied or with a circuit varying the voltage fed

into the comparator terminal (see fig.1).

4/8

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