MP6536 - 26V, 5.5A 3-CHANNEL POWER HALF-BRIDGE

MP6536 Rev. 1.01

www.MonolithicPower.com

9

5/3/2018

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OPERATION

The MP6536 is a 3-channel half-bridge driver

intended to drive a brushless DC motor. The

output is in phase with the input, and the dead

time is optimized for symmetrical performance,

regardless of load conditions.

When SHDN is low, all channels are off. When

STBYB is pulled low, it causes the outputs of all

the channels to go into high impedance. However,

when the voltage across BST1/2/3 and SW1/2/3

drops low significantly, the bottom MOSFET is

turned on to refresh the external bootstrap

capacitor. Connecting a capacitor (

0.1μF or

greater) between BST and SW (as the bootstrap

capacitor) is recommended.

In order to prevent erratic operation, two under-

voltage lockout (UVLO) circuits are used. One

ensures that the supply for the bottom gate drive

circuit is sufficiently high, and the other is for the

top gate driver.

Fault Protection

To protect the power MOSFETs, an internal

current limit of 5.5A is set for all MOSFETs.

When this limit is reached, all MOSFETs of the

over-current bridge channel will go into high

impedance

for

a

fixed

duration

(30µs

approximately) before resuming normal operation.

Thermal monitoring is integrated into the MP6536.

If the die temperature rises above 160ºC, all

switches are turned off. The temperature must

fall

below

125ºC

before

normal

operation

resumes.

To enhance the robustness of the device under a

short-circuit

condition,

a

capacitor

can

be

connected to FAULTB (see Fig. 2). The time

constant of the RC must be greater than 50ms

for the FAULTB node to reach 2V. Under a short-

circuit condition, the FAULTB node re-sets to

zero, and the part is placed in standby mode until

the voltage at STBYB is above 2V.

FIGURE 2. Fault Protection Enhancement Circuit

Fault Output

The MP6536 includes an open drain, active-low

fault indicator output (FAULTB). A fault is

indicated if one of the following conditions is

detected:

1. The current limit is tripped.

2. Thermal shutdown is tripped.

A fault on any channel causes FAULTB to pull

low. Once the fault is removed, the MP6536

resumes normal operation.

Do not apply more than 6V to FAULTB.

Error Reporting

The MP6536 has two fault monitor pins (FLT3B

and FLT2B), which are active low open-drain

outputs. They provide protection-mode signaling

to a PWM controller or another system control

device (see Table 1).

TABLE 1. Fault Output Logic

OCP

OTP

UVP

FLTB2

FLTB3

0

0

0

1

1

0

0

1

0

1

0

1

0

1

0

1

0

0

0

0