MP6522

– 35V, 3.2A, H-BRIDGE MOTOR DRIVER

1.0MP6522 Rev. 1.01

www.MonolithicPower.com

9

4/17/2018

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2018 MPS. All Rights Reserved.

OPERATION

The MP6522 is an H-bridge motor driver that

integrates four N-channel power MOSFETs with

3.2A of peak current capability. The MP6522

operates over a wide 5.4V to 35V input voltage

range and is designed to drive DC brush motors,

solenoids, and other loads.

Current Sensing

The

current

flowing

in

the

two

low-side

MOSFETs is sensed with an internal current-

sensing circuit. A voltage proportional to the

output current is sourced on VISEN.

The VISEN output voltage scaling is set by a

resistor connected between ISET and ground.

For 1A of output current, 100µA of current is

sourced into the resistor connected to VISEN.

For example, if a 10kΩ resistor is connected

between ISET and ground, the output voltage

on VISEN is 1V/A of output current.

The current is sensed when one of the low-side

MOSFETs is turned on, including during slow

decay (brake) mode.

The load current applied to VISEN should be

kept below 2mA with no more than 500pF of

capacitance.

Current Limit and Regulation

The current in the outputs is limited using

constant-off-time pulse-width modulation (PWM)

control circuitry.

In PWM, a diagonal pair of MOSFETs is turned

on initially and drives current through the load.

The current increases in the load, which is

sensed by the internal current-sense circuit. If

the

load

current

reaches

the

current-trip

threshold, the H-bridge switches to slow decay

mode with the two low-side MOSFETs turned

on.

After a fixed off-time (t

falls at least 20% below the current-limit

threshold, the MOSFETs are re-enabled and

the cycle repeats. If the current is still higher

than this level, the off time is extended until the

current falls to 20% below the current limit

threshold.

The current-limit threshold is reached when

VISEN reaches 1.5V. For example, with a 10k

Ω

resistor from ISET to ground, the VISEN

voltage is 1V/A of output current. Therefore,

when the current reaches 1.5A, the VISET

voltage reaches 1.5V, and a current trip occurs.

During

current

regulation,

nFAULT

is

not

activated.

Blanking Time

There is often a current spike during start-up

due to the

body diode’s reverse-recovery

current or the shunt capacitance of the load.

This current spike requires filtering to prevent it

from erroneously shutting down the high-side

blanks

the

output

of

the

current-sense

comparator when the outputs are switched.

This blanking time also sets the minimum on

time for the high-side MOSFET.

Input Logic

For the MP6522, control of the outputs is

accomplished through IN1 and IN2 (see Table

1).

Table 1: Output Control Pins

IN1

IN2

OUT1

OUT2

Function

0

0

Z

Z

Coast

0

1

L

H

Forward

1

0

H

L

Reverse

1

1

L

L

Brake (low)

nSLEEP Operation

Driving nSLEEP low puts the device into a low-

power sleep state. In this state, all internal

circuits including the gate drive charge pump

are disabled, and the H-bridge outputs are

turned off. All inputs are ignored when nSLEEP

is active low. When waking up from sleep mode,

approximately 1ms of time must pass before

the outputs can operate.

Fault

The MP6522 provides an nFAULT pin, which is

driven active low if any protection circuits (over-

current, over-voltage, over-temperature) are

activated. nFAULT is not driven low when a

current-limit trip occurs. nFAULT is an open-

drain output and requires an external pull-up

resistor. When the fault condition is removed,

nFAULT is pulled inactive high by the pull-up

resistor.