MP6509 – 2.7V-TO-18V, 1.2A STEPPER MOTOR DRIVER

MP6509 Rev.1.0

www.MonolithicPower.com

13

8/28/2014

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ATT1

ATT2

Attenuation Ratio

L

L

100%

H

L

80%

L

H

50%

H

H

20%

The formula used to calculate the output current

limit when using the function for attenuating the

REF

LIMIT

SENSE

V

I

Attenuation Ratio

R

=×

(2)

Sleep Mode

The MP6509 provides low-power standby sleep

mode.

Connect the nSLEEP pin to logic low to enable a

low-power sleep state. In this state, the two full

bridges are disabled and the internal circuits

such as the gate drive, internal regulator, and

charge pump all shut down. Connect the

nSLEEP pin to logic high to wake up the MP6509

from sleep mode, though there is a delay time of

~1ms until the internal circuitry stabilizes.

Blanking Time

There is usually a current spike during the

switching transition due to the body diode’s

reverse-recovery current or the distributed

inductance or capacitance. This current spike

requires filtering to prevent it from erroneously

shutting down the high-side MOSFET. An

the current sense comparator when the outputs

are switched, which is also the minimum on time

for high-side MOSFET.

Enable

If all the inputs (AIN1, AIN2, BIN1 and BIN2) are

logic low, the MP6509’s outputs are disabled

while the charger pump and internal regulator

remain active.

Synchronous Rectifier

The MP6509 enters a synchronous rectifier (SR)

mode during the constant off-time period when

the current limit threshold is exceeded, and the

load current freewheels in slow decay SR mode.

In slow decay mode, the current freewheels

through one low-side MOSFET and the body

diode of the other low-side MOSFET to short the

winding. The SR mode enables both two low-side

MOSFETs, which feature a lower voltage drop

and lower power dissipation during decay

operation.

Over-Current Protection

The over-current protection circuit limits the

current through the FET by disable the gate

driver. If the over-current limit threshold is

reached and lasts for longer than the over-

current deglitch time, all MOSFETs in the H-

bridge will be disabled and the nFAULT pin will

be driven low. The driver will remain disabled and

is reset to enable state after 2ms(typ). Please

note that only the H-bridge in which the OCP is

detected will be disabled while the other bridge

will operate normally.

Over-current conditions on both high and low

side devices; i.e., a short to ground, supply, or

across the motor winding will all result in an over-

current

shutdown.

Note

that

over-current

protection does not use the current sense

circuitry used for PWM current control, and is

independent of the sense resistor value or VREF

voltage.

Thermal Shutdown

The junction temperature of the IC is internally

monitored. If the junction temperature exceeds

the threshold value (typically 165ºC), the

converter is shut down (the fault pin goes low)

and recoveries once the junction temperature

drops to about 150ºC (15ºC hysteresis).

UVLO protection

The MP6509 has UVLO protection. When the

VIN exceeds the UVLO rising threshold, the

MP6509 powers up. It shuts off when VIN drops

below the UVLO falling threshold.