L6208QTR STMicroelectronics, L6208QTR Datasheet - Page 16

• Manufacturer Part Number: L6208QTR
• Description: Motor / Motion / Ignition Controllers & Drivers DMOS Dual Full Bridge Driver 5.6A
• Manufacturer: STMicroelectronics

Specifications of L6208QTR

• Product Category: Motor / Motion / Ignition Controllers & Drivers
• Rohs: yes

Circuit description
4.4
16/33
Decay mode
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.
OFF time, both of the power MOSFETs are switched off and the current recirculates through
the two opposite freewheeling 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
MOSFET 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 may
decay completely to zero during the OFF time. At this point, if both of the power MOSFETs
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 MOSFET is
operated in synchronous rectification mode. This operation is called Quasi-Synchronous
Rectification Mode. When the monostable times out, the power MOSFETs are turned on
again after some delay set by the dead time to prevent cross conduction.
Figure 17
time, the lower power MOSFET 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 MOSFET is operated in the synchronous rectification mode.
When the monostable times out, the lower power MOSFET is turned on again after some
delay set by the dead time to prevent cross conduction.
Figure 16. Fast decay mode output stage configurations
Figure 17. Slow decay mode output stage configurations
) A
) A
O
O
N
N
shows the operation of the bridge in slow decay mode. At the start of the OFF
Figure 16
I T
I T
M
M
E
E
D01IN1335
D01IN1336
shows the operation of the bridge in fast decay mode. At the start of the
) B
) B
Doc ID 018710 Rev 2
1
1
μs DEAD TIME
μs DEAD TIME
C) QUASI-SYNCHRONOUS
C) SYNCHRONOUS
RECTIFICATION
RECTIFICATION
D) 1μs SLOW DECAY
D) 1μs DEAD TIME
L6208Q