tda5144t NXP Semiconductors, tda5144t Datasheet - Page 11

• Manufacturer Part Number: tda5144t
• Description: Brushless Dc Motor Drive Circuit
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The oscillation of the motor is given by:
where:
Example: J = 72
and I = 0.5 A; this gives f
then a start frequency of 2 Hz can be chosen or
t = 500 ms, thus C = 0.5/2 = 0.25 F (choose 220 nF).
T
CAP-DC)
In this circuit capacitor CAP-CD is charged during one
commutation period, with an interruption of the charging
current during the diode pulse. During the next
commutation period this capacitor (CAP-CD) is discharged
at twice the charging current. The charging current is
8.1 A and the discharging current 16.2 A; the voltage
range is from 0.9 to 2.2 V. The voltage must stay within
this range at the lowest commutation frequency of
interest, f
If the frequency is lower, then a constant commutation
delay after the zero-crossing is generated by the discharge
from 2.2 to 0.9 V at 16.2 A;
maximum delay = (0.076
Example: nominal commutation frequency = 900 Hz and
the lowest usable frequency = 400 Hz; so:
The other capacitor, CAP-DC, is used to repeat the same
delay by charging and discharging with 15.5 A. The same
value can be chosen as for CAP-CD. Figure 9 illustrates
typical voltage waveforms.
June 1994
f
CAP-CD
C
osc
HE ADAPTIVE COMMUTATION DELAY
K
I = current (A)
p = number of magnetic pole-pairs
J = inertia J (kg.m
Brushless DC motor drive circuit
=
t
= torque constant (N.m/A)
=
8.1 10
------------------------- -
f 1.3
---------------------------------- -
2
C1
=
:
K
---------------------- -
6231
------------ -
400
1
t
–
6
J
I p
=
10
=
6231
------------ -
2
f
C1
)
15.6
6
kg.m
osc
(C in nF)
(choose 18 nF)
C) ms (with C in nF).
= 5 Hz. If the damping is high
2
, K = 25
(CAP-CD
10
3
N.m/A, p = 6
AND
11
Product specification
TDA5144