MP3422—6.5A, 600KHZ HIGH EFFICIENCY, SYNCHRONOUS, STEP-UP CONVERTER WITH OUTPUT DISCONNECT IN 2X2MM QFN PACKAGE

MP3422 Rev.1.01

www.MonolithicPower.com

12

8/6/2014

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Current Sensing

Lossless current sensing converts the NMOS

switch current signal to a voltage which is

summed with the internal slope compensation.

The summed signal is compared to the error

amplifier output to provide a peak current

control command for the PWM. Minimum peak

switch current limit is 6.5A. The switch current

signal is blanked for about 60ns internally to

enhance noise rejection.

Output Disconnect

The MP3422 is designed to allow true output

disconnect

by

eliminating

body

diode

conduction of the internal PMOS rectifier. This

It also allows for inrush current limit at start-up,

minimizing surge current seen by the input

supply. To obtain the advantage of output

disconnect, there must not be an external

Schottky diode connected between the switch

Over Load and Short Circuit Protection

When an overload or a short circuit occurs, the

output voltage will drop. If Vout drops below

Vin+0.3V, the MP3422 will convert to step down

mode. If Vout drops below 1.7V, the device will

convert to linear charge mode. If Vout drops

below about 70% of the nominal output voltage,

the MP3422 will immediately shut down and re-

start after about 40μs as a new power-on cycle.

Over Voltage Protection

If Vout is higher than 7V, boost switching stops.

This prevents overvoltage from damaging the

internal power MOSFET.

When the output

drops below 7V, the device resumes switching

automatically.

Thermal Shutdown

The device contains an internal temperature

monitor.

The switches turn off if the die

temperature exceeds 150°C. The device will

resume

normal

operation

below

130°C.