MP9518

–SINGLE-PHASE, BLDC, MOTOR DRIVER WITH INTEGRATED HALL SENSOR

MP9518 Rev.1.0

www.MonolithicPower.com

9

7/24/2017

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© 2017 MPS. All Rights Reserved.

OPERATION

The MP9518 is a single-phase, brushless, DC

motor driver with integrated power MOSFETs

and a hall-effect sensor.

Speed Control

The MP9518 is controlled using a PWM input

interface, which is compatible with industry-

standard devices. The IC detects the PWM

input signal duty cycle and linearly controls the

H-bridge output duty cycle, so the fan speed

increases as the input duty cycle increases.

The PWM input accepts a wide input frequency

range (12kHz to 48kHz), while the output

frequency is kept constant at 26kHz above the

audible frequency range.

PWM Output Drive

The

IC

controls

the

H-bridge

MOSFET

switching

to

reduce

speed

variation

and

increase system efficiency (see Figure 2).

When the rotor magnet pole S comes around,

the internal hall sensor outputs high. When the

rotor magnet pole N comes around, the internal

high interval, the OUT2 and OUT1 switching

status can be

divided

to different

timing

sections (see Figure 2).

θ

e

OUT1

OUT2

θ

son

θ

soff

θ

off

θ

son

θ

soff

θ

off

S

N

S

N

Figure 2: Timing Diagram

Soft Turn-On Section

During this time, OUT1 continues switching,

and the duty cycle increases gradually from 0 to

the target setting duty cycle in 16 steps max.

OUT2 remains low. Determine the duration time

from

the

linear

interpolation

between

the

SON_100 (23.9°) and SON_12P5 (45°) bits

setting value.

Normal PWM Switching Section

During this time, OUT1 continues switching,

and the duty cycle is fixed at the target setting

duty. OUT2 remains low.

Soft Turn-Off Section

During this time, OUT1 continues switching,

and the duty cycle gradually decreases from the

target setting duty cycle to 0 in 16 steps max.

OUT2 remains low. Determine the duration time

from

the

linear

interpolation

between

the

SOFF_100 (45°) and SOFF_12P5 (23.9°) bits

setting value.

Off Section

During

this

time,

OUT1

remains

at

high

impedance. OUT2 remains low. The time

duration is adaptive from 0° to 45°. In steady

state, this function block tries to maintain the

phase lock of the hall output falling edge and

winding current zero-crossing edge.

For a hall output low interval, the conducting

phase changes, but the switching sequence

remains the same.

Protection Circuits

The MP9518 is fully protected against over-

voltage,

under-voltage,

over-current,

over-

temperature

events,

and

input

reverse

protection.

Over-Current Protection (OCP)

The MP9518 protects against internal overload

and short circuit by detecting current flowing

through each MOSFET. If the current flowing

through any MOSFET exceeds the over-current

protection (OCP) threshold after around 1.5µs

of blanking time, that MOSFET turns off

immediately. After approximately 3.6s of delay,

the bridge is re-enabled automatically.

Overload Current Limit

During normal switching, if the current flowing

through the high-side MOSFET (HS-FET) of the

H-bridge exceeds the threshold set by the

register SUCL bits after around 1.5µs of

blanking time, the HS-FET turns off immediately.

The HS-FET resumes switching in the next

switching cycle. The overload current limit is

fixed at around 860mA.