tda5240t NXP Semiconductors, tda5240t Datasheet - Page 13

• Manufacturer Part Number: tda5240t
• Description: Brushless Dc Motor Drive Circuit
• Manufacturer: NXP Semiconductors

.
Philips
then a start frequency
THE ADAPTIVE COMMUTATION DELAY (CAP-CDM
during the diode pulse. During the next commutation
current. The charging current is 8.1 J.lA and the discharging
voltage must stay within this range at the lowest commutation
Example: J = 72 x 10---6 kg/m2, K = 25 x 10-3 N.m/A, p = 6 and I = 0.5 A; this gives f osc = 5 Hz. If the damping
In this circuit capacitor CAP-CDM
If the frequency
2.2 to 0.9 Vat 16.2I1A.
The other capacitor, CAP-CDS, is used to repeat the same delay by charging and discharging with 20 ~.
The same value can be chosen as for CAP-CDM. Figure 7 illustrates typical voltage waveforms
Example: nominal commutation frequency = 900 Hz and the lowest usable frequency = 400 Hz, so:
THE TIMING CAPACITOR (CAP- TI)
Capacitor
internal delays.
November
Brushless
Semiconductors
CAP- TI is used for timing the successive
96
is lower, then a constant commutation
DC motor drive circuit
Fig.7
of 2 Hz can be chosen or t = 500 ms, thus C = 0.5/2 = 0.25 ~F, (choose 220 nF).
voltoge l\
on CAP-DC I ~
CAP-CDM
is charged during one commutation
(ZCR=ZERO-CROSSING
maximum delay = (0.076 x C) ms (witch C in nF)
ZCR
ICOM
I
CAP-CDM = ~=
and CAP-CDS
I
I
p = number of magnetic pole-pairs
c=
ZCR
Kt = torque constant (N.m/A)
I
! COM
AND CAP-CDS)
iXT:3
rT\
J = inertia J (kg/m2)
8.1
I
period this capacitor (CAP-CDM)
steps within one commutation
I = current (A)
ZCR
voltage
ICOM
delay after the zero-crossing
I ~
I
I
-5
where:
13/19
-~
-fC1
I
current 16.2 J.lA ; the voltage range is from 0.9 to 2.2 V. The
15.6 (choose 18 nF)
; COM=COMMUTATION)
ZCR
frequency
waveforms
I
I rr\
I
COM COM I COM
(C in nF)
period, with an interruption
ZCR
I ~
I
of interest, fc1 :
in normal
I
i
ZCR
1
I I
period; these steps include some
is generated
running
t~
is discharged
mode.
of the charging current
by the discharge
Product specification
at twice the charging
TDA5240T
is high
from