L292(1993) Ver la hoja de datos (PDF) - STMicroelectronics

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L292
(Rev.:1993)

SWITCH-MODE DRIVER FOR DC MOTORS

STMicroelectronics 

L292

It is possible to verify that the L292 works in "closed-

loop" conditions during the entire motor current

rise-time: the voltage at pin 7 inverting input of the

error amplifier) is locked to the reference voltage

VR, present at the non-inverting input of the same

amplifier.

The previous linear analysis is correct for this ex-

ample.

Descresing the ξ value, the rise-time of the current

decreases. But for a good stability, from relationship

(6), the maximum value of ξ is:

ξmin

=

1

2 4√

2

(phase margin = 45°)

b) Large signal reponse

The large step signal response is limited by slew-

rate and inductive load.

In this case, during the rise-time of the motor

current, The L292 works is open-loop condition.

CLOSED LOOP SYSTEM BANDWIDTH.

A good choice for x is the value 1 / √2. In this case :

IM

VI

(s)

=

0.044

Rs

1 + s RF CF

1 + 2s RF CF + 2s 2 RF 2 CF 2

(8)

The module of the transfer function is :

|

IM

VI

|

=

0.044

Rs

2

√1+ω2RF2CF2

√[ ( 1+2ωRFCF)2+1]•[(1−2ωRFCF)2+1 ]

(9)

The cutoff frequency is derived by the expression (9) by putting

which :

|

IM

VI

|

=

0.707

•

0.044

Rs

(−3 dB),

from

ωT

=

0.9

RF CF

fT

=

0.9

2π RF CF

9/12

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