MP6600

– 35V, 1.5A, STEPPER MOTOR DRIVER W/ INTERNAL CURRENT SENSE

MP6600 Rev. 1.01

www.MonolithicPower.com

12

12/27/2017

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© 2017 MPS. All Rights Reserved.

OPERATION

The MP6600 is a bipolar, stepper motor driver

that

integrates

eight

N-channel

power

MOSFETs arranged as two full-bridges with

1.5A of current capability each. The MP6600

operates over a wide 4.5V to 35V voltage

supply range.

The MP6600 is designed to operate bipolar

stepper motors in full-, half-, quarter-, and

eighth-step modes. At each step, the current of

each full-bridge is set by the output voltage of a

DAC, which is controlled by the output of the

translator.

The currents in each of the two outputs are

regulated with programmable, constant off-time,

pulse-width modulation (PWM) control circuitry.

The MP6600 integrates internal current sensing

with no external sense resistors required.

Stepping

The motor moves step-by-step by applying a

series of pulses to STEP. A rising edge on the

STEP input sequences the translator and

advances the motor by one increment. The

translator controls the input to the DACs and

the direction of current flow in each winding.

The amplitude of the increment (step size) is

determined by the state of the inputs (MS1 and

MS2) (see Table 1).

The state of DIR determines the direction of the

rotation of the stepper motor.

The minimum STEP pulse width is 1µs. The

logic control inputs MSx and DIR require at

least 200ns of set-up time and hold time to the

rising edge of the STEP input (see Figure 2).

Step

MSx, DIR

Figure 2: STEP Timing Diagram

Programmable Constant Off-Time Current

Control

The

motor

current

is

regulated

by

a

programmable constant off-time PWM current

control circuit.

Initially, a diagonal pair of MOSFETs turns on

and drives current through the motor winding.

The current increases in the motor winding,

which is sensed by an internal current sense

the high-side MOSFET (HS-FET) always turns

on in spite of current limit detection.

When the current reaches the current trip

threshold, the internal current comparator either

shuts off the HS-FET so the winding inductance

current freewheels through the two low-side

MOSFETs (LS-FET) (slow decay) or turns on

another diagonal pair of MOSFETs so the

current flows back to the input (fast decay). The

current continues decreasing for the constant

off-time duration unless a zero current level is

detected. Afterward, the HS-FET is enabled to

increase the winding current again. The cycle

then repeats.

can be approximated with Equation (1):

OFF

OSC

t

(ns)

115 R

(k )







(1)

The full-scale (100%) regulation current can be

calculated with Equation (2):

Max

ISET

I

71k / R



(2)

The DAC output reduces the trip current in

precise steps. Calculate the trip current with

Equation (3):

Max

Trip

Trip

I

I

I



 %

(3)