AN1625 STMicroelectronics, AN1625 Datasheet - Page 33

• Manufacturer Part Number: AN1625
• Description: L6235 THREE PHASE BRUSHLESS DC MOTOR DRIVER
• Manufacturer: STMicroelectronics

Motor Data
Winding Resistance (2 phases):
Winding Inductance (2 phases):
Supply Voltage:
Polar Couples:
Referring to approximated formulae in Figure 24, it's possible to calculate the Duty Cycle (D), the Switching Fre-
quency (f
The on-time is t
The bulk capacitor needs to withstand at least 24 V + 5% + 25% 32 V. A 50 V capacitor will be used. Allowing
a voltage ripple of 200 mV, the capacitor ESR should be lower than 200 mV / 1A = 200 m ; the AC current
capability should be about 1.5 A (worst case).
Providing a reference voltage of 0.5 V, 0.33
PR
uses recommended components (1N4148 diodes, ceramic capacitors and a 100
R = 24 k , C = 470 pF are connected to the RC pins, obtaining t
placed, and the pin is driven by the
With these values, in case of short circuit between two OUT pins or an OUT pin and GND, the PowerDMOS
turns off after about 1 s, and t
Figure 36. Application Example.
Referring to Figure 23, Figure 24, Figure 25, the dissipating power is about 2.37 W. If the ambient temperature
is lower than 50 °C, with 5 cm
estimated junction temperature is about 97 °C.
Logic Supply
Irms
18 k
+
2 k 0.25 W
-
5 V
1%
1%
0.25 W
SW
2
· R
), the Current Ripple ( I). With a 8 µs off-time, we will have:
SENSE
Custom Logic
ON
V
= D / f
µC
or
ref
= 0.5 V
· D
SW
Ceramic
5.6 nF
0.37 W. Three 1
100 k
12.5 µs, which is far from the minimum allowed (1.5 µs).
DISABLE
2
of copper area on the PCB, a ground layer and a PowerSO36 package, the
1
2
24 V +/- 5%
800 H
D
H1
H2
H3
CW/CCW
BRAKE
EN
DIAG
V
C through a 100 k
OUT
ref
Ceramic
47nF
1
61%, f
OUT
240 s.
2
OUT
3
RC
sensing resistor are needed. The resistors power rating is about
SW
/ 0.25 W - 1% resistors in parallel are used. The charge pump
PULSE
Brushless DC Motor
TACHO
L6235
24 k
49 kHz, I
3-Phase
V
1%
BOOT
1N4148
0.25W
100
RC
resistor.
OFF
CP
Ceramic
470 pF
10nF 50V
Ceramic
1N4148
GND
OFF
GND
320 mA.
V
SA
GND
SENSE
SENSE
V
7.8 s. On the EN pin a 5.6 nF has been
SB
GND
A
B
220nF 35V
AN1625 APPLICATION NOTE
Ceramic
1
, 0.25 W, 1%
3 X
resistor to reduce EMI).
ESR<200m
100µF 50V
100nF 50V
Ceramic
V
S
+
= 24 V
-
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