DRV10983ZPWPR datasheet(37/58 Pages) TI1

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MotorSpeed[15:8]

Motor Speed Read Back

Read

MotorSpeed[7:0]

Read

MotorSpeed[15:8]

I C send out motor speed.

MotorSpeed[7:0]

MotorSpeed

Buffer[7:0]

DRV10983

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SLVSCP6C – JULY 2014 – REVISED MAY 2016

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9.4.11.2.1

Two-Byte Register Read Back

Several of the registers such as MotorSpeed report data that is contained in two registers.

To make sure that the data does not change between the reading of the first and second register reads, the

DRV10983 implements a special scheme to synchronize the reading of MSB and LSB data. To ensure valid data

is read when reading a two register value, use the following sequence.

1. Read the MSB.

2. Read the LSB.

Figure 38 shows the two-register readback circuit. When the MSB is read, the controller takes a snapshot of the

LSB. The LSB data is stored in one extra register byte, which is shown as MotorSpeedBuffer[7:0]. When the LSB

is read, the value of MotorSpeedBuffer[7:0] is sent.

Figure 38. Two-Byte Register Read Back

9.4.11.3 Motor Electrical Period Read Back

The motor operation electrical period is automatically updated in register MotorPeriod1 and MotorPeriod2 while

the motor is spinning. MotorPeriod1 is the MSB and MotorPeriod2 is the LSB. The electrical period is measured

as the time between calculated BEMF zero crossings for phase U. The electrical period of the motor is denoted

as d as ‘tELE_PERIOD (µs)’ and is calculated as shown in Equation 8.

tELE_PERIOD (µs) = {MotorPeriod1:MotorPeriod2} × 10

(8)

As an example consider the following:

MotorPeriod1 = 0x01;

MotorPeriod2 = 0xFF;

tELE_PERIOD = 512 (0x01FF) × 10 = 5120 µs

The motor electrical period and motor speed satisfies the condition of Equation 9.

tELE_PERIOD (s) × Velocity (Hz) = 1

(9)

9.4.11.4 Motor Velocity Constant Read Back

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

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 10.

Ktc (V/Hz)= {MotorKt1:MotorKt2} / 2 /1090

(10)

9.4.11.5 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.

DRV10983ZPWPR Datasheet(PDF) 37 Page - Texas Instruments

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