L6235QTR STMicroelectronics, L6235QTR Datasheet - Page 15

• Manufacturer Part Number: L6235QTR
• Description: Motor / Motion / Ignition Controllers & Drivers DMOS 3-Phase Brushless DC Motor
• Manufacturer: STMicroelectronics

Specifications of L6235QTR

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

L6235Q
4.4
4.5
Slow decay mode
Figure 13
time only two legs of the 3-phase bridge are active, therefore, only the two active legs of the
bridge are shown in the figure and the third leg is off. At the start of the OFF 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 reducing the impedance of the freewheeling diode and the related conducting losses.
When the monostable times out, the upper power MOSFET that was operating the
synchronous mode turns off and the lower power MOSFET is turned on again after some
delay set by the dead time to prevent cross conduction.
Figure 13. Slow decay mode output stage configurations
Decoding logic
The decoding logic section is a combinatory logic that provides the appropriate driving of the
3-phase bridge outputs according to the signals coming from the three Hall sensors that
detect rotor position in a 3-phase BLDC motor. This novel combinatory logic discriminates
between the actual sensor positions for sensors spaced at 60, 120, 240 and 300 electrical
degrees. This decoding method allows the implementation of a universal IC without
dedicating pins to select the sensor configuration.
There are eight possible input combinations for three sensor inputs. Six combinations are
valid for rotor positions with 120 electrical degrees sensor phasing (see
1, 2, 3a, 4, 5 and 6a) and six combinations are valid for rotor positions with 60 electrical
degrees phasing (see
common (1, 2, 4 and 5) whereas there are two combinations used only in 120 electrical
degrees sensor phasing (3a and 6a) and two combinations used only in 60 electrical
degrees sensor phasing (3b and 6b).
The decoder can drive motors with different sensor configurations simply by following
Table
(OUT
output configuration 6a is the same as 6b.
The sequence of the Hall codes for 300 electrical degrees phasing is the reverse of 60 and
the sequence of the Hall codes for 240 phasing is the reverse of 120. So, by decoding the 60
and the 120 codes it is possible to drive the motor with all four conventions by changing the
direction set.
1
2. For any input configuration (H1, H2 and H3) there is one output configuration
, OUT
) A
O
shows the operation of the bridge in slow decay mode during the OFF time. At any
N
I T
M
2
E
and OUT
D01IN1336
Figure
3
). The output configuration 3a is the same as 3b and analogously
) B
15, positions 1, 2, 3b, 4, 5 and 6b). Four of them are used in
Doc ID 018997 Rev 2
1
μs DEAD TIME
C) SYNCHRONOUS
RECTIFICATION
Figure
Circuit description
D) 1μs DEAD TIME
14, positions
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