EVAL6229PD STMicroelectronics, EVAL6229PD Datasheet - Page 16

• Manufacturer Part Number: EVAL6229PD
• Description: EVAL BOARD FOR L6229PD SOIC
• Manufacturer: STMicroelectronics

Specifications of EVAL6229PD

• Mfg Application Notes: L6235, AN1625 App Note
• Main Purpose: Power Management, Motor Control
• Embedded: No
• Utilized Ic / Part: L6229PD SOIC
• Primary Attributes: 3-Ph BLDC, 8 ~ 52V Output, PWM Current Control, Brake Function
• Secondary Attributes: Over Current, Cross Conduction & Temperature Protection
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5491

AN1451 APPLICATION NOTE
2.11.2 Decay Modes
The CONTROL input is used to select the behavior of the bridge during the off time. When the CONTROL pin
is low, the Fast Decay mode is selected and both transistors in the bridge are switched off during the off time.
When the CONTROL pin is high, the Slow Decay mode is selected and only the low side transistor of the bridge
is switched off during the off time.
Figure 15 shows the operation of the bridge in the Fast Decay mode. At the start of the off time, both of the power
MOS are switched off and the current recirculates through the two opposite free wheeling diodes. The current
decays with a high di/dt since the voltage across the coil is essentially the power supply voltage. After the dead
time, the lower power MOS in parallel with the conducting diode is turned on in synchronous rectification mode.
In applications where the motor current is low it is possible that the current can decay completely to zero during
the off time. At this point if both of the power MOS were operating in the synchronous rectification mode it would
then be possible for the current to build in the opposite direction. To prevent this only the lower power MOS is
operated in synchronous rectification mode. This operation is called Quasi-Synchronous Rectification Mode.
When the monostable times out, the power MOS are turned on again after some delay set by the dead time to
prevent cross conduction.
Figure 16 shows the operation of the bridge in the Slow Decay mode. 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 slowly. After the dead time the upper power MOS is operated in the synchro-
nous rectification mode. When the monostable times out, the lower power MOS is turned on again after some
delay set by the dead time to prevent cross conduction.
Figure 15. Fast Decay Mode Output Stage Configurations
A) ON TIME
B) 1 s DEAD TIME
C) QUASI-SYNCHRONOUS
D) 1 s SLOW DECAY
RECTIFICATION
D01IN1335
Figure 16. Slow Decay Mode Output Stage Configurations
A) ON TIME
B) 1 s DEAD TIME
C) SYNCHRONOUS
D) 1 s DEAD TIME
RECTIFICATION
D01IN1336
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