MCT8317A datasheet(33/161 Pages) TI1

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Brake

Brake_Rou ne

Brake_Rou ne_End

Time >

BRK_TIME

Figure 8-19. Brake Routine

Power-On State

This is the initial state of the Motor Start Sequence (MSS) when MCT8317A

is powered on. In this state, MCT8317A configures the peripherals,

initializes the algorithm parameters from EEPROM and prepares for driving

the motor.

Sleep/Standby

In this state, SPEED_REF/TARGET_DUTY is set to zero and MCT8317A

is either in sleep or standby mode depending on DEV_MODE and SPEED/

WAKE pin voltage.

SPEED_REF/TARGET_DUTY >

0 Judgement

When SPEED_REF is set to greater than zero, MCT8317A exits the

sleep (SPEED pin voltage > VIL)/standby state and proceeds to ISD_EN

judgement. As long as SPEED_REF is set to zero, MCT8317A stays in

sleep/standby state.

ISD_EN Judgement

MCT8317A checks to see if the initial speed detect (ISD) function is

enabled (ISD_EN = 1b). If ISD is enabled, MSS proceeds to the BEMF

< STAT_DETECT_THR judgement. Instead, if ISD is disabled, the MSS

proceeds directly to the BRAKE_EN judgement.

BEMF < STAT_DETECT_THR

|| BEMF < FG_BEMF_THR

Judgement

ISD determines the initial condition (speed, angle, direction of spin) of the

motor (see Section 8.3.9.1). If motor is deemed to be stationary (BEMF

< STAT_DETECT_THR || BEMF < FG_BEMF_THR), the MSS proceeds

to BEMF < STAT_DETECT_THR judgement. If the motor is not stationary,

MSS proceeds to verify the direction of spin.

STAT_BRK_EN Judgement

The MSS checks if the stationary brake function is enabled (STAT_BRK_EN

=1b). If the stationary brake function is enabled, the MSS advances to the

stationary brake routine. If the stationary brake function is disabled, the MSS

advances to motor start-up state (see Section 8.3.9.4).

Stationary Brake Routine

The stationary brake routine can be used to ensure the motor is completely

stationary before attempting to start the motor. The stationary brake is

applied by turning on all three low-side driver MOSFETs for a time

configured by STARTUP_BRK_TIME.

Direction of spin Judgement

The MSS determines whether the motor is spinning in the forward or

the reverse direction. If the motor is spinning in the forward direction,

the MCT8317A proceeds to the RESYNC_EN judgement. If the motor is

spinning in the reverse direction, the MSS proceeds to the RVS_DR_EN

judgement.

RESYNC_EN Judgement

If RESYNC_EN is set to 1b, MCT8317A proceeds to BEMF >

RESYNC_MIN_THRESHOLD judgement. If RESYNC_EN is set to 0b, MSS

proceeds to HIZ_EN judgement.

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MCT8317A

SLLSFQ2 – JANUARY 2023

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