MP6605C

– 4-CHANNEL LOW-SIDE DRIVER WITH I2C INTERFACE

MP6605C Rev. 1.0

MonolithicPower.com

10

7/11/2022

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OPERATION

The MP6605C is a 4-channel low-side driver that

integrates four N-channel power MOSFETs and

four clamp diodes with 1.5A of current capability

per channel. The MP6605C operates across a

wide 4.5V to 60V supply voltage range.

The MP6605C is designed to drive inductive

loads, including unipolar stepper motors and

solenoids.

Unipolar Stepper Operation

A unipolar stepper motor has two windings.

These windings are driven by currents that are

90° out of phase. Each winding has a center tap

that is connected to the power source. The

current is driven through the winding in a push-

pull fashion, meaning that the device alternately

pulls one side of the winding to ground, then it

pulls the other side. This reverses the current,

which then reverses 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. The current flows

from ground to the power supply through the

opposite MOSFET body diode.

Leakage Inductance Clamp (VCLAMP)

A unipolar stepper motor has a leakage

inductance because the two halves of the

winding are not perfectly coupled. If a MOSFET

turns off, the voltage exceeds 2 x VIN for a short

period. This leakage inductance spike must be

clamped to prevent over-voltage (OV) conditions

on the MOSFETs.

If a switch turns off when driving a solenoid

connected to the VIN pin, current must continue

to flow until the magnetic field decays.

These currents flow through internal diodes at

each output to a common VCLAMP pin.

Generally, the VCLAMP pin is connected to a

transient voltage suppressor that limits the

voltage on the output pins to a maximum of 60V,

regardless of VIN voltage.

If

the outputs do not need to exceed the VIN pin’s

supply, connect VCLAMP to VIN.

RESET and nENBL Operation

Driving the RESET pin active high initializes the

digital logic. The I2C interface and outputs are

disabled while RESET is active.

The nENBL pin controls the output drivers. When

nENBL is low, the outputs are enabled, and

signals on the I2C interface are recognized.

When nENBL is high, the outputs are disabled,

and the I2C interface remains operational.

nENBL has an internal pull-down resistor.

Address Input Pins

The four address input pins (A0~A3) are

intended to either be connected to ground or

floating. These pins are connected to an internal

voltage (about 6V) via an internal pull-up resistor.

This means that these pins require special

consideration when they are driven by a logic

output.

Logic Input Pins

The remaining logic input pins have Schmitt

trigger inputs with a hysteresis. These pins are

compatible with 3V or 5V logic.

Fault Reporting

The MP6605C provides an nFAULT pin that

reports if a fault condition (such as over-current

protection (OCP), over-voltage protection (OVP),

or over-temperature protection (OTP)) occurs.

nFAULT is an open-drain output that is driven

low when 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 the

device exceeds the OC limit threshold for longer

than the OC deglitch time, all of the MOSFETs

are disabled, and nFAULT is driven low. The

driver automatically re-enables itself after about

2.5ms.

Input Under-Voltage Lockout (UVLO)

Protection

If VIN falls below the under-voltage lockout

(UVLO) threshold voltage, all circuitry in the

device is disabled, and the internal logic is reset.

Operation resumes when VIN rises above the

UVLO threshold.

Over-Temperature Protection (OTP)

If the die temperature exceeds its safe limits, the

outputs are disabled, and nFAULT is driven low.