DRV10975ZPWPR datasheet(40/65 Pages) TI1

40 / 65 page

DRV10975, DRV10975Z

SLVSCP2E – JANUARY 2015 – REVISED MAY 2018

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8.4.11.4 BEMF Constant Readback

For any given motor, the integrated value of BEMF during half of an electronic cycle will be constant, Ktc (see

Lock2: Abnormal Kt).

The integration of the motor BEMF is processed periodically (updated every electrical cycle) while the motor is

spinning. The result is stored in register MotorKt1 and MotorKt2.

The relationship is shown in Equation 11.

Ktc (V/Hz)= {MotorKt1:MotorKt2} / 2 /1442

(11)

8.4.11.5 Motor Estimated Position by IPD

After inductive sense is executed the rotor position is detected within 60 electrical degrees of resolution. The

position is stored in register IPDPosition.

The value stored in IPD Position corresponds to one of the six motor positions plus the IPD Advance Angle as

shown in Table 7. For more about information about IPD, see Initial Position Detect (IPD).

Table 7. IPD Position Readback

Rotor position (°)

120

180

240

300

Data1

128

171

213

IPD Advance

Angle

120

Data2

(Data1 + Data2) mod (256)

8.4.11.6 Supply Voltage Readback

The power supply is monitored periodically during motor operation. This information is available in register

SupplyVoltage. The power supply voltage is recorded as shown in Equation 12.

VPOWERSUPPLY (V) = Supply Voltage × 22.8 V / 256

(12)

8.4.11.7 Speed Command Readback

The DRV10975 converts the various types of speed command into a speed command value (SpeedCmd) as

shown in Figure 38. By reading SpeedCmd, the user can observe PWM input duty (PWM digital mode), analog

voltage (analog mode), or I2C data (I2C mode). This value is calculated as shown in Equation 13.

Equation 13 shows how the speed command as a percentage can be calculated and set in SpeedCmd.

DutySPEED (%) = SpeedCmd × 100% / 255

where

•

DutySPEED = Speed command as a percentage

•

SpeedCmd = Register value

(13)

8.4.11.8 Speed Command Buffer Readback

If acceleration current limit and AVS are enabled, the PWM duty cycle output (read back at spdCmdBuffer) may

not always match the input command (read back at SpeedCmd) shown in Figure 38. See AVS Function and

Current Limit.

By reading the value of spdCmdBuffer, the user can observe buffered speed command (output PWM duty cycle)

to the motor.

DRV10975ZPWPR Datasheet(PDF) 40 Page - Texas Instruments

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