MP8046 –28V, 5A DUAL CHANNEL POWER HALF-BRIDGE

MP8046 Rev. 0.92

www.MonolithicPower.com

7

4/29/2010

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OPERATION

The MP8046 is a high voltage, dual channel

power half- bridge that can be configured as the

output of a Class D amplifier. The output is in

phase with the input, and the dead time is

optimized

for

symmetrical

performance,

regardless of load conditions.

channels 1 and 2 will be shut off. When the

outputs of both channels to go into high

impedance. However, when the voltage across

the BST1/2 and OUT1/2 pins drops sufficiently

low, the bottom MOSFET is turned on to refresh

the

external

bootstrap

capacitor.

For

a

bootstrap capacitor of 100nF, the refresh time is

approximately 300ns.

In order to prevent erratic operation, two under

voltage lockout (UVLO) circuits are used. One

of them is to ensure 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, two layers of

protection are provided. The first is the current

limit, wherein if the current through either the

top or the bottom MOSFET exceeds an

internally preset value of 5A, that particular

MOSFET is immediately shut down and the

complementary MOSFET is turned on. If this

fails to reset the current and there is an

indication that the current is going to runaway,

the current foldback will kick in. This ensures

that the current is reset close to zero before

resuming operation.

Thermal monitoring is also integrated into the

MP8046. If the die temperature rises above

150

°C, both switches are turned off. The

temperature must fall below 130

°C before

normal operation resumes.

To enhance the robustness of the device under

short circuit condition, a capacitor can be

1. The time constant of the RC is selected to be

node will be reset to zero and the part will be

place in standby mode until the voltage at the

STBY

pin is above 1V.

Figure 1— Fault Protection Circuit

Fault Output

The MP8046 includes an open drain, active low

indicated if the current limit is tripped or the

thermal shutdown is tripped.

be pulled low. However, only that fault channel

has its output set to high impedance.