MP6601 – 35V, 2.5A, STEPPER MOTOR DRIVER W/ INTERNAL CURRENT SENSE

MP6601 Rev. 1.01

www.MonolithicPower.com

11

9/4/2018

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slow decay is engaged again for another fixed

off time. After the completion of this second

fixed off time, a new PWM cycle begins.

Figure 2 shows the automatic decay mode

operation during a current reduction as a result

of a change in xI0 or xI1.

In some cases (specifically high voltage and

low inductance or regulation of very small

currents), the minimum on time of the PWM

cycle (set by the blanking time described above)

can cause the current to rise very quickly. In

this case, both slow and fast decay are used

(see Figure 3).

Figure 3: Current Regulation of Low Current/Low

Inductance

Sleep Operation (nSLEEP)

Driving nSLEEP low puts the device into a low-

power sleep state. In this state, the gate drive

charge pump is stopped, and all internal circuits

and H-bridge outputs are disabled. All inputs

are ignored when nSLEEP is active low.

When

waking

up

from

sleep

mode,

approximately 1ms of time must pass before

issuing a step command to allow the internal

circuitry time to stabilize. nSLEEP has an

internal pull-down resistor.

Fault (nFAULT)

The MP6601 provides an nFAULT pin that

reports to the system if a fault condition occurs,

such as over-current protection (OCP), over-

temperature protection (OTP), or over-voltage

protection (OVP). nFAULT is an open-drain

output type and is driven low when a fault

condition occurs. If the fault condition is

released, 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

current reaches the over-current limit threshold

and stays there for longer than the over-current

deglitch time, all MOSFETs in the H-bridge are

disabled, and nFAULT is driven low. The driver

is disabled for 5ms, typically. Afterward, the

driver is re-enabled automatically.

Over-current conditions on both the high- and

low-side devices (i.e.: a short to ground, supply,

or across the motor winding) result in an over-

current shutdown. Note that OCP does not use

the current-sense circuitry used for PWM

current control.

Over-Voltage Protection (OVP)

If the input voltage on VIN is higher than the

OVP threshold, the H-bridge output is disabled,

and nFAULT is driven low. This protection is

released when VIN drops below 38V.

Input UVLO Protection

If at any time the voltage on 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.

Thermal Shutdown

If the die temperature exceeds safe limits, all

MOSFETs in the H-bridge are disabled, and

nFAULT

is

driven

low.

Once

the

die

temperature has fallen to a safe level, operation

resumes automatically.