TDA7272A datasheet(10/16 Pages) STMICROELECTRONICS

10 / 16 page

Inverting input of main amplifier. In this pin the

current reference programmed at pins 20, 17 is

compared with the current from the monostable

(stream of rectangular pulses).

In steady-state condition (constant motor speed)

the values are equal and the capacitor CF voltage

is constant.

This means for the speed n (min 1):

10.435

CT kRP

where ”k” is the number of collector segments.

(poles)

The non inverting input of the main amplifier is in-

ternally connected to a reference voltage (2.3 V).

Pin 15

Ground.

Pin 16

Ground.

Pin 17

Left speed adjustment. The voltage at this pin is

fixed to a reference value of 0.8 V. A resistor from

this pin and ground (fig. 14) fixes the reference

current which will be compared with the medium

output current of the monostable in order to fix the

speed of the motor at the programmed value. The

correct value of Rp would be :

10.435

CT kn

n = motor speed, (min -1)

k = poles number

The control of speed can be done in different

way:

- speed separately programmed in two

senses of rotation (fig. 14-15) ;

- only one speed for the two senses of rota-

tion (fig. 16) ;

- speeds of the two senses a bit different (i.e.

for compensating different pulley effects)

(fig. 17) ;

- speed programmed with a DC voltage (fig.

18) i.e. with DA converter ;

Figure 14.

Figure 15.

Figure 16.

Figure 17.

TDA7272A

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