DRV10983-Q1 Datasheet, PDF (28/72 Pages) Texas Instruments – Automotive, Three-Phase, Sensorless BLDC Motor Driver

DRV10983-Q1
SLVSD14 – JUNE 2017
www.ti.com
Table 5. Configuration Options for Controlling Open-Loop Motor Start
DESCRIPTION
Open- to closed-loop threshold
Align time
First-order accelerate
Second-order accelerate
Open-loop current setting
Align current setting
Open-loop current ramping
REG. NAME
CONFIG4
CONFIG4
CONFIG4
CONFIG4
CONFIG3
CONFIG3
CONFIGURATION
BITS
Op2ClsThr[4:0]
AlignTime[2:0]
StAccel[2:0]
StAccel2[2:0]
OpenLCurr[1:0]
OpLCurrRt[2:0]
MIN. VALUE
0.8 Hz
40 ms
0.019 Hz/s
0.0026 Hz/s²
200 mA
150 mA
0.023 V_CC/s
MAX. VALUE
204.8 Hz
5.3 s
76 Hz/s
57 Hz/s²
1.6 A
1.2 A
6 V_CC/s
8.4.3.6 Start-Up Timing
Start-up timing is determined by the align and accelerate time. The align time can be set by AlignTime[2:0]. The
accelerate time is defined by the open-to-closed loop threshold Op2ClsThr[4:0] along with the first-order
StAccel[2:0](A1) and second-order StAccel2[2:0](A2) accelerate rates. Figure 21 shows the motor start-up
process.
Speed
Speed =
A1 ´ t + 0.5 A2 ´ t²
Close loop
Op2ClsThr
AlignTime
Accelerate Time
Time
Accelerate Time is determined by
Op2ClsThr and A1, A2.
Figure 21. Motor Start-Up Process
Select the first-order and second-order accelerate rates to allow the motor to reliably accelerate from zero
velocity up to the closed-loop threshold in the shortest time possible. Using a slow accelerate rate during the first
order accelerate stage can help improve reliability in applications where it is difficult to accurately initialize the
motor with either align or IPD.
Select the open-to-closed loop threshold to allow the motor to accelerate to a speed that generates sufficient
BEMF for closed-loop control. This is determined by the velocity constant of the motor based on the relationship
described in Equation 2.
BEMF = Kt_PH × speed (Hz)
(2)
8.4.4 Align Current
During the align state, the measured align current is dependent on actual motor resistance and r_DS(on) of the
internal FETs. The relationship between measured align current and configured align current is derived from
actual motor resistance, configured motor resistance and r_DS(on).
AlignCurrent
_
Measured
=
AlignCurrent
_
Configured
´
é
ê
R_m
êë^Rmotor ^{+ r}DS(on)
ù
ú
úû
where
• AlignCurrent_Measured is the actual align current measured during the align state
• AlignCurrent_Configured is the align current configured by OpenLCurr[1:0]
• R_motor is the actual motor resistance
• r_DS(on) is the resistance between the drain and source of the FETs during the on-state
• R_m is configured by Rm[6:0]
(3)
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