MP6

508 – 2.7V-TO-18V, 1.2A STEPPER MOTOR DRIVER

MP6508 Rev.1.0

www.MonolithicPower.com

10

6/27/2017

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© 2017 MPS. All Rights Reserved.

OPERATION

The MP6508 is a motor driver that integrates 8

N-channel power MOSFETs for dual, internal full-

bridges with 1.2A output current capability over

an input voltage range of 2.7V to 18V. It can

drive a stepper motor, or two DC motors.

The motor output current can be either controlled

by an external pulse width modulator (PWM) or

internal PWM current controller.

The

MP6508

includes

the

following

fault

protections: over-current protection(OCP), under-

voltage

lockout(UVLO)

and

over-temperature

protection(OTP).

It also provides a low-power sleep mode.

External PWM Current Control

The motor current can be regulated by applying

external PWM signals on the input pins AIN1,

AIN2, BIN1 and BIN2. For phase A, the AIN1 and

AIN2 input pins control the state of the AOUT1

and AOUT2; similarly for phase B, the BIN1 and

BIN2 input pins control the state of the BOUT1

and BOUT2.

Gate

Driver

Motor

VIN

AOUT1

AOUT2

AIN1

AIN2

SENA

WindingA

Figure 2: Full-Bridge Control Circuit

Figure 2 shows the input signal logic and bridge

output state.

Table 1: Full-Bridge Gate Logic

A/BIN1

A/BIN2

A/BOUT1

A/BOUT2

L

L

High

Impedance

High

Impedance

L

H

GND

VIN

H

L

VIN

GND

H

H

GND

GND

In external PWM control mode, the

winding’s

inductive current ramps up when the high-side

MOSFET is on and freewheels during the high-

side

MOSFET’s

off

time

to

cause

the

recirculation current.

There are two modes for this recirculation current:

slow decay and fast decay, both of which are

shown in Figure 3 for forward operation and

Figure 4 for reverse operation.

VIN

AOUT1

AOUT2

Slow Decay

Fast Decay

Forward

Figure 3: Forward Operation

VIN

AOUT1

AOUT2

Slow Decay

Fast Decay

Reverse

Figure 4: Reverse Operation

For slow decay mode, the current circulates

through the two low-side MOSFETs. For fast

decay mode, the current flows through the body

diodes of the other diagonal two MOSFETS.

To configure the MP6508 for fast decay mode,

apply the PWM signal to one input pin and keep