Datasheet

Pin 9
Output motor left. The four power transistors are
realized as darlington structures. The arrange-
ment is controlled by the logic status at pins 18
and 19.
As before explained (see block description), in the
normal left or right mode one of the lower dar-
lington becomes saturated whereas the other re-
mains open. The upper half of the bridge oper-
ates in the linear mode.
In stop condition both upper bridge darlingtons
are off and both lower are on. In the high output
impedance state the bridge is switched com-
pletely off.
Connecting the motor between pins 9 and 12
both left or right rotation can be obtained. If only
one rotation sense is used the motor can be con-
nected at only one output, by using only the upper
bridge half. Two motors can be connected each
at the each output : in such case they will work al-
ternatively(see application section).
The internal diodes, together with the collector
substrate diodes, protect the output from induc-
tive vol-tage spikes during the transition phase
(fig. 10)
Pin 10
Common sense output. From this pin the output
current of the bridge configuration (motor current)
is fed into R
S
external resistor in order to gener-
ate a proper voltage drop.
The drop is supplied into pin 1 for tachometric
control and into pin 8 for V/I control (see pin 1 and
pin 8 sections).
Pin 11
Supply voltage.
Pin 12
Output motor right. (see pin 9 section)
Pin 13
Output main amplifier. The voltage on this pin re-
sults from the tachometric speed control and
feeds the output stage.
The value of the capacitor C
F
(fig. 11), connected
from pins 13 and 14, must be chosen low enough
in order to obtain a short reaction time of the
tachometric loop, and high enough in order to re-
duce the output ripple.
A compromise is reached when the ripple voltage
(peak-to-peak)V
ROP
is equal to 0.1 V
MOTOR
:
C
F
= 2.3
C
T
V
RIP
( 1 −
R
T
R
P
)
with V
RIP
=
V
FEM
+ I
MOT
⋅ R
MOT
10
and with duty cy-
cle = 50 %. (see pin 2-3 section)
Figure 8.
Figure 9.
Figure 10.
TDA7272A
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