MP6606

– 60V, 8-CHANNEL LOW-SIDE DRIVER WITH SERIAL INTERFACE

MP6606 Rev. 1.0

MonolithicPower.com

10

3/11/2022

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OPERATION

The MP6606 is an 8-channel low-side driver

that

integrates

eight

N-channel

power

MOSFETs and eight clamp diodes, each of

which have a current capability of 750mA. The

MP6606 operates over a wide 4.5V to 60V

supply voltage range.

The MP6606 is designed to drive inductive

loads, including unipolar stepper motors and

solenoids.

Unipolar Stepper Operation

A unipolar stepper motor has two windings that

are driven with currents that are 90° out of

phase. Each winding has a center tap, which is

connected to the power source. Current is

driven through the winding in a push-pull

fashion, which means the sides of the winding

are alternately pulled to ground. This reverses

the current and the magnetic field.

After a MOSFET turns off due to the inductance

of the winding, current continues to flow through

the other side of the winding. This current flows

from ground through the opposite MOSFET

body diode to the power supply.

Leakage Inductance Clamp (VCLAMP)

In a unipolar stepper, the two halves of the

winding are not perfectly coupled, which results

in leakage inductance. When a MOSFET turns

off, the voltage rises up to twice its normal

supply

for

a

short

period.

This

leakage

inductance spike must be clamped to protect

the MOSFETs from over-voltage damage.

When driving a solenoid connected to VIN,

when the switch turns off, current must continue

to flow until the magnetic field decays. This

current goes to the VCLAMP pin.

These currents flow through the internal diodes

from each output to a common VCLAMP pin.

Generally, VCLAMP is connected to a transient

voltage suppressor. This limits the voltage on

the

output

pins

to

a

maximum

of

60V,

regardless of VIN voltage.

If it is not required for the outputs to exceed the

input voltage (VIN) supply, connect VCLAMP to

VIN.

The internal diodes can support 750mA of

current at a maximum 20% duty cycle.

RESET and ENBL Operation

Driving the RESET pin active high initializes the

digital logic. The serial interface and outputs are

disabled while RESET is active.

The ENBL pin controls the output drivers. When

ENBL is high, the outputs are enabled, and

signals on the serial interface are recognized.

When ENBL is low, the outputs are disabled,

and the serial interface remains operational.

ENBL has an internal pull-down resistor.

Logic Input Pins

All other logic inputs use a Schmitt trigger input

buffer

with

a hysteresis.

These pins are

compatible with a 3.3V or 5V logic.

Fault Reporting

The MP6606 provides an nFAULT pin that

reports if a fault condition (such as over-current

protection

(OCP)

or

over-temperature

protection (OTP)) occurs. nFAULT is an open-

drain output that is driven low if a fault condition

occurs. If the fault condition is removed,

nFAULT is pulled high by an external pull-up

resistor.

Over-Current Protection (OCP)

OCP circuitry limits the current through the

MOSFETs by disabling the gate driver. If OUTx

exceeds the over-current threshold for longer

than the over-current deglitch time, all the

MOSFETs are disabled, and nFAULT is driven

low. The driver automatically re-enables itself

after a period of time.

Input Under-Voltage Lockout (UVLO)

Protection

If the voltage on the VIN (VIN) pin falls below the

under-voltage lockout (UVLO) threshold, all of

the circuitry in the device is disabled, and the

internal logic is reset. Operation resumes when

VIN rises above the UVLO threshold.

Thermal Shutdown

If the die temperature exceeds its safe limits,

the outputs are disabled, and nFAULT is driven

low. Operation resumes automatically when the

die temperature returns to a safe level.