MP6631 – 24V, 3A PEAK, THREE-PHASE BLDC MOTOR DRIVER

MP6631 Rev. 1.1

MonolithicPower.com

12

2/21/2023

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OPERATION

The MP6631 is a three-phase brushless DC

(BLDC) motor driver with integrated power

MOSFETs. The MP6631 controls the motor

speed via the pulse-width modulation (PWM)

signal or the DC voltage on the PWM/DC pin,

with closed/open-loop speed control and a built-

in, configurable speed curve function. The

device supports a single external Hall-effect

sensor or triple external Hall-effect sensors.

The MP6631 also features a rotational speed

detector. The rotational speed detector (the

FG/RD pin) is an open-drain output. It outputs a

high or low voltage relative to the external Hall

signal. Additionally, direction control is achieved

via the DIR pin

’s input.

Rich protection features include under-voltage

lockout (UVLO), locked-rotor protection, over-

current

protection

(OCP),

and

thermal

shutdown.

A sinusoidal drive is employed in the MP6631.

Figure 4 shows the MP6631

’s output drive,

where HA, HB, and HC are the outputs of Hall

A, Hall B, and Hall C, respectively.

OUTA

Duty

OUTB

Duty

OUTC

Duty

HB

HA

HC

001

101

100

110

010

011

001

iA

iB

iC

Figure 4: MP6631 Hall Output and Output Drive

Speed Control

The PWM/DC pin controls the motor speed in

an open loop or closed loop via the PWM signal

or the DC voltage. PWM/DC accepts a wide

input frequency range (1kHz to 100kHz) or a 0V

to 1.2V voltage.

If DC_PWM = 1, then the motor speed is

controlled via the DC voltage on the PWM/DC

pin. The DC voltage range is 0V to 1.2V.

If DC_PWM = 0, then the motor speed is

controlled via the input PWM signal duty cycle.

The input PWM frequency range is 1kHz to

100kHz.

Starting Duty and Minimum Speed

The starting duty is configured by the DIN_MIN

bits. When the PWM input duty is below the

duty set by DIN_MIN, the fan speed supports

two modes:

1. The speed maintains the minimum speed

when SPD_ZERO is set to 0.

2. The speed is at 0 when SPD_ZERO is set

to 1.

Speed Curve Configuration

The SPD_MAX registers configure the speed

when

the

input

PWM

duty

is

at

100%.

Otherwise, the MP6631 provides a five-point

curve configuration function where the output

speed can be configured when the input duty is

37.5%, 50%, 62.5%, 75%, or 87.5%. Linear

interpolation occurs between the adjacent duty

cycles.

The DIN_MIN register sets the starting duty,

and SPD_MIN sets the minimum output duty

(open-loop

control)

and

minimum

speed

(closed-loop control).

Figure 5 shows the curve configuration when

SPD_ZERO = 1.

37.5% 50% 62.5% 75% 87.5% 100%

Input PWM Duty

DIN_MIN

D37.5

D50

D62.5

D75

D87.5

SPD_MAX

Speed

Figure 5: Curve Configuration when

SPD_ZERO = 1