MP9184 – 17A, 600KHZ, 20V WIDE INPUT RANGE ,SYNCHRONOUS BOOST CONVERTER IN ASMALL 3X4MM QFN PACKAGE

MP9184 Rev. 1.0

www.MonolithicPower.com

14

8/27/2015

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APPLICATION INFORMATION

Selecting Current Limit Resistor

When an external resistor is used, MP9184 has

(connected from the input voltage to SENSE),

CL

CL

SENSE

IV / R



UVLO Hysteresis

The MP9184 features a programmable UVLO

hysteresis. When powering up, EN sinks a 4.5μA

2). VIN voltage must increase to overcome the

current sink. The VIN start-up threshold is

determined by:

TOP

IN ON

EN ON

TOP

BOT

R

VV

(1

) 4.5 A R

R



 



 

(1.33V, typically).

sink current turns off to create a reverse

hysteresis for the VIN falling threshold:

IN UVLO HYS

TOP

V4.5 A R



 

MP9184

VIN

EN

4.5 A

Selecting the Soft-Start Capacitor

To prevent excessive input current, the MP9184

includes a soft-start circuit that limits the voltage

on

COMP

during

start-up

This

prevents

premature termination of the source voltage at

start-up due to input-current overshoot. When

power is applied to the device, enable is asserted

and a 7μA internal-current source charges the

external capacitor at SS. The SS voltage clamps

COMP voltage (as well as the inductor peak

current) until output is close to regulation or

COMP reaches 1.8V. For most applications, a

33nF SS capacitor is sufficient.

Setting the Output Voltage

Output voltage is fed back through two sense

resistors in series. The feedback reference

voltage is 1.225V, typically. The equation for the

output voltage is:

)

2

1

1

(

R

R

V

V

REF

OUT







Where, R1 is the top feedback resistor, R2 is the

reference voltage (1.225V, typically).

Choose feedback resistors in the 10kΩrange (or

higher) for good efficiency.

Selecting the Input Capacitor

An input capacitor is required to supply the AC

ripple current to the inductor while limiting noise

at the input source. A low ESR capacitor is

required to minimize noise. Ceramic capacitors

are preferred, but tantalum or low ESR

electrolytic capacitors suffice.

Two 22uF capacitors are recommended for high-

power applications. The capacitor can be

electrolytic, tantalum, or ceramic. However, since

the capacitor absorbs the input-switching current,

it requires an adequate ripple-current rating. Use

a capacitor with a RMS current rating greater

than the inductor-ripple current (see “Selecting

the Inductor” to determine the inductor-ripple

current).

To ensure stable operation, place the input

capacitor as close to the IC as possible.

Alternately, a smaller, high-quality ceramic 0.1μF

capacitor may be placed closer to the IC with the

larger capacitor placed a little farther away.

When using this technique, a larger electrolytic or

tantalum type capacitor is recommended. All

ceramic capacitors should be placed very close

to the input.