AN1625 STMicroelectronics, AN1625 Datasheet - Page 9

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

D1, D2
R4
C5
C8
Due to the high charge pump frequency, fast diodes are required. Connecting the cold side of the bulk capacitor
(C8) to V
= 100
in all conditions. 1N4148 diodes withstand about 200 mA DC (1 A peak), and the maximum reverse voltage is 75
V, so they should fit for the majority of applications.
2.7 Sharing the Charge Pump Circuitry
If more than one device is used in the application, it's possible to use the charge pump from one L6235 to supply
the V
Figure 8. A 100 nF capacitor (C8) should be connected to the V
Supply voltage pins (V
The higher the number of devices sharing the same charge pump, the lower will be the differential voltage avail-
able for gate drive (V
In this case it's recommended to omit the resistor on the CP pin, obtaining a higher current capability of the
charge pump circuitry.
Better performance can also be obtained using a 33 nF capacitor for C5 and using schottky diodes (for example
BAT47).
Sharing the same charge pump circuitry for more than 3÷4 devices is not recommended, since it will reduce the
V
Figure 8. Sharing the charge pump circuitry.
BOOT
BOOT
To other Devices
voltage increasing the high-side MOS on-resistance and thus power dissipation.
); at startup (when V
S
instead of GND the average current in the external diodes during operation is less than 10 mA (with R4
pins of several ICs. The unused CP pins on the slaved devices are left unconnected, as shown in
: 1N4148
: 100
: 10 nF 100V ceramic
: 220 nF 35V ceramic
BOOT
To High-Side
Gate Drivers
(1/8 W)
S
) of the devices sharing the charge pump must be connected together.
V
BOOT
- V
S
S
is provided to the IC) is less than 200 mA while the reverse voltage is about 10 V
), causing a higher R
CP
V
SA
L6235
V
SB
C18 = 100 nF
DS(ON)
for the high side DMOS, so higher dissipating power.
V
BOOT
BOOT
To High-Side
Gate Drivers
D1 = BAT47
pin of each device.
C5 = 33nF
AN1625 APPLICATION NOTE
CP
D2 = BAT47
V
SA
L6235
V
SB
C8 = 100nF
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