MCT8317A datasheet(52/161 Pages) TI1

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Driving State

Low-Side Braking

HSA

LSA

LSB

HSC

LSC

HSB

HSA

LSA

LSB

HSC

LSC

HSB

Figure 8-40. Low-Side Braking

The MCT8317A can also enter low-side braking through BRAKE pin input. When BRAKE pin is pulled to

HIGH state, the output speed is reduced to a value defined by BRAKE_DUTY_THRESHOLD prior to turning all

low-side MOSFETs ON. In this case, MCT8317A stays in low-side brake state till BRAKE pin changes to LOW

state.

8.3.17.4 High-Side Braking

High-side braking mode is configured by setting MTR_STOP to 011b. When a motor stop command is received,

the output speed is reduced to a value defined by ACT_SPIN_BRK_THR prior to turning all high-side MOSFETs

ON (see example Figure 8-41) for a time configured by MTR_STOP_BRK_TIME. If the motor speed is below

ACT_SPIN_BRK_THR prior to receiving stop command, then the MCT8317A transitions directly into the brake

state. After applying the brake for MTR_STOP_BRK_TIME, the MCT8317A transitions into Hi-Z state by turning

OFF all MOSFETs.

Driving State

High-Side Braking

HSA

LSA

LSB

HSC

LSC

HSB

HSA

LSA

LSB

HSC

LSC

HSB

Figure 8-41. High-Side Braking

8.3.17.5 Active Spin-Down

Active spin down mode is configured by setting MTR_STOP to 100b. When motor stop command is received,

MCT8317A reduces duty cycle to ACT_SPIN_BRK_THR and then transitions to Hi-Z state by turning all

MOSFETs OFF. The advantage of this mode is that by reducing duty cycle, the motor is decelerated to a

lower speed thereby reducing the phase currents before entering Hi-Z. Now, when motor transitions into Hi-Z

state, the energy transfer to power supply is reduced. The threshold ACT_SPIN_BRK_THR needs to configured

high enough for MCT8317A to not lose synchronization with the motor.

8.3.18 FG Configuration

The MCT8317A provides information about the motor speed through the Frequency Generate (FG) pin. In

MCT8317A, the FG pin output is configured through FG_CONFIG. When FG_CONFIG is configured to 1b, the

FG output is active as long as the MCT8317A is driving the motor. When FG_CONFIG is configured to 0b, the

MCT8317A provides an FG output until the motor back-EMF falls below FG_BEMF_THR.

MCT8317A

SLLSFQ2 – JANUARY 2023

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