MP6543 – 12V, 2A, THREE-PHASE POWER STAGE

MP6543 Rev. 1.01

www.MonolithicPower.com

14

1/15/2020

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To terminate the outputs when using an A/D

converter with inputs that are ratiometric to its

supply voltage, use two equal-value resistors to

the ADC supply and ground. The resulting ADC

code will be half-scale at zero current. Figure 2

shows a simplified drawing of the current

measurement circuit.

Figure 2: Current Measurement Circuit Diagram

Automatic Synchronous Rectification

When driving current through an inductive load, if

the output MOSFETs are both turned off, the

recirculation current must continue to flow. This

current is normally passed through the MOSFET

body

diodes.

To

prevent

excess

power

dissipation in the body diodes, the MP6543

implements automatic synchronous rectification.

When both the HS-FET and LS-FET are turned

off and the voltage on an Sx output pin is driven

below ground, the LS-FET turns on until the

current flowing through it reaches zero, or the

HS-FET turns on. Similarly, if the voltage on the

Sx pin rises above VIN, the HS-FET turns on until

the current reaches zero, or the LS-FET turns on.

nFAULT Output

The MP6543 provides an nFAULT output pin,

which is driven active low in a fault condition,

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

temperature protection (OTP). This pin is an

open-drain output, and must be pulled up by an

external pull-up resistor.

Input UVLO Protection

If the voltage on VIN falls below the UVLO

threshold, all circuitry in the device is disabled

and the internal logic is reset. Normal operation

resumes when VIN rises above the UVLO

threshold.

Thermal Shutdown

If the die temperature exceeds safe limits, all

output FETs are disabled and nFAULT is driven

low. Normal operation resumes when the die

temperature has fallen to a safe level.

Over-Current Protection

The OCP circuit limits the current through each

FET by disabling its gate driver. If the over-

current limit threshold is reached, and lasts for

longer than the over-current deglitch time, all six

output FETs are disabled (outputs become high-

impedance) and nFAULT is driven low. The

current is then recirculated through the body

diodes. The over-current shutdown is latched

until either nSLEEP is reset or VIN is power-

cycled.

Over-current conditions on both high-side and

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

or across the motor winding) all result in an over-

current shutdown. Figure 3 shows a simplified

diagram of the OCP circuit for one output.

OC

Comparator

OC_REF

VIN

Sx

LSS

HS Sense Amp

LS Sense Amp

Small

FET

Large

FET

Large

FET

OC

Small

FET

Matched

Matched

Figure 3: OCP Circuit

OC_ADJ values are outside the specified value

range for over-current threshold.

Table 3: Over-Current Threshold

OC_ADJ Resistor

Value

Typ OC Threshold

0

6.2A

Float

7.2A

3.3V LDO Output

An internal LDO regulator generates a 3.3V

voltage with 100mA capacity, which can be used

to power a small low-power microcontroller. A

bypass capacitor between 4.7µF and 10µF is

required from the V3P3 pin to ground.