MCT8317A datasheet(35/161 Pages) TI1

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can be disabled by setting ISD_EN to 0b. If the function is disabled (ISD_EN set to 0b), the MCT8317A does not

perform the initial speed detect function and proceeds to check if the brake routine (BRAKE_EN) is enabled.

8.3.9.2 Motor Resynchronization

The motor resynchronization function works when the ISD and resynchronization functions are both enabled and

the device determines that the initial state of the motor is spinning in the forward direction (same direction as

the commanded direction). The speed and position information measured during ISD are used to initialize the

drive state of the MCT8317A, which can transition directly into closed loop state without needing to stop the

motor. In the MCT8317A, motor resynchronization can be enabled/disabled through RESYNC_EN bit. If motor

resynchronization is disabled, the device proceeds to check if the motor coast (Hi-Z) routine is enabled.

8.3.9.3 Reverse Drive

The MCT8317A uses the reverse drive function to change the direction of the motor rotation when ISD_EN

and RVS_DR_EN are both set to 1b and the ISD determines the motor spin direction to be opposite to

that of the commanded direction. Reverse drive includes synchronizing with the motor speed in the reverse

direction, reverse decelerating the motor through zero speed, changing direction, and accelerating in open

loop in forward (or commanded) direction until the device transitions into closed loop in forward direction

(see Figure 8-20). MCT8317A uses the same parameter values for open to closed loop handoff threshold

(OPN_CL_HANDOFF_THR), open loop acceleration rates (OL_ACC_A1, OL_ACC_A2) and open loop current

limit (OL_ILIMIT) in the reverse direction as in the forward direction..

Reverse Deceleration

Open Loop

Handoff to close loop

Open loop

Close loop

Speed

Time

Handoff to open loop

Figure 8-20. Reverse Drive Function

8.3.9.4 Motor Start-up

There are different options available for motor start-up from a stationary position and these options can be

configured by MTR_STARTUP. In align and double align mode, the motor is aligned to a known position by

injecting a DC current. In IPD mode, the rotor position is estimated by applying 6 different high-frequency pulses.

In slow first cycle mode, the motor is started by applying a low frequency cycle.

8.3.9.4.1 Align

Align is enabled by configuring MTR_STARTUP to 00b. The MCT8317A aligns the motor by injecting a DC

current using a particular phase pattern (phase-C high-side FET and phase-B low-side FET are ON) - current

flowing into phase-B and flowing out from phase-C for a certain time configured by ALIGN_TIME.

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MCT8317A

SLLSFQ2 – JANUARY 2023

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MCT8317A Datasheet(PDF) 35 Page - Texas Instruments