L6229 STMicroelectronics, L6229 Datasheet - Page 12

• Manufacturer Part Number: L6229
• Description: DMOS DRIVER FOR THREE-PHASE BRUSHLESS DC MOTOR
• Manufacturer: STMicroelectronics

L6229
Figure 13. Area where t
can vary maintaining the PWM regulation.
ON
100
10
1.5µs (typ. value)
1
0.1
1
10
100
Coff [nF]
3.4 SLOW DECAY MODE
Figure 14 shows the operation of the bridge in the Slow Decay mode during the Off Time. At any time only two
legs of the three-phase bridge are active, therefore only the two active legs of the bridge are shown in the figure
and the third leg will be off. At the start of the Off Time, the lower power MOS is switched off and the current
recirculates around the upper half of the bridge. Since the voltage across the coil is low, the current decays slow-
ly. After the Dead Time the upper power MOS is operated in the synchronous rectification mode reducing the
impendence of the freewheeling diode and the related conducting losses. When the monostable times out, up-
per MOS that was operating the synchronous mode turns off and the lower power MOS is turned on again after
some delay set by the Dead Time to prevent cross conduction.
Figure 14. Slow Decay Mode Output Stage Configurations
A) ON TIME
B) 1µs DEAD TIME
C) SYNCHRONOUS
D) 1µs DEAD TIME
RECTIFICATION
D01IN1336
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