MP3414 – 1.8A, 1MHZ, SYNCHRONOUS, STEP-UP CONVERTER WITH OUTPUT DISCONNECT

MP3414 Rev 1.05

www.MonolithicPower.com

10

3/30/2018

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2018 MPS. All Rights Reserved.

quiescent

power

dissipation

as

well

as

switching power loss. The OUT pin voltage-

monitoring circuit and error amplifier with loop

compensation for peak-current– mode control

remain active.

The output ripple, which is usually around 1%

peak to peak, can be reduced by increasing the

output capacitance and also by adding a small

feed-forward capacitance (around 10pF).

The MP3414 operates from PSM to PWM mode

depending on the load, which varies with the

input voltage, inductor value, and the output

capacitor value.

Under-Voltage Lockout

Under-voltage lockout prevents device startup

the battery is being discharged.

Error Amplifier

The error amplifier (EA) is an internally-

compensated amplifier. The EA compares the

generate an error signal. The output voltage of

MP3414 could be adjusted from 1.8V to 4V by

connecting FB to the tap of an external voltage

equation:

R1

OUT

R2

V1.21V (1

)

 

(1)

Set R1 and R2 as large as possible to achieve

a low quiescent current. Usually, select an R1

value larger than 300k for good stability and

transient balance.

Current Sensing

Lossless current sensing converts the NMOS

switch current signal to a voltage that can be

summed with the internal slope compensator.

The difference between this summed signal and

the error amplifier output provides control over

the peak current through the PWM. Peak switch

current is limited to approximately 1.8A,

independent of input or output voltage. The

switching current signal is blanked for 60ns to

enhance noise rejection.

Thermal Protection

The device has an internal temperature monitor

If the die temperature exceeds 150°C, the

switches turn off. Once the output drops below

1.7V, it will turn on.

Output Disconnect and Inrush Limiting

The MP3414 is designed to allow true output

disconnect by eliminating the internal PMOS

rectifier’s body diode conduction. This feature

draw 0A from the input source. It also allows for

inrush current limiting at start-up, which

minimizes surge currents at the input supply.

Note that to optimize output disconnect,

exclude the external Schottky diode between

To minimize voltage overshoot on the SW pin

due to stray inductance, keep the output filter

and use very low ESR/ESL ceramic capacitors

tied to a clean ground plane.

Short-Circuit Protection

Unlike most step-up converters, the MP3414

allows for short circuits on the output. In the

event of a short circuit, the device first turns off

the NMOS when the sensed current reaches

the current limit. The device then enters a linear

charge period with the current limited as with

the start-up period. In addition, the thermal

regulation circuit further controls the input

current if the die temperature rises above

150°C.

The MP3414 will continue to regulate the output

voltage even when the input voltage exceeds

the output voltage. This is achieved by

terminating the switching at the synchronous

This ensures that the slope of the inductor

current will reverse while current flows to the

output. Since the PMOS no longer acts as a

low-impedance switch in this mode, power

dissipation increases within the IC to cause a

sharp drop in efficiency. Limit the maximum

output current to maintain an acceptable

junction temperature.