MPQ4460 datasheet(15/18 Pages) MPS

15 / 18 page

MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER

MPQ4460 Rev1.21

www.MonolithicPower.com

12/5/2012

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

External Bootstrap Diode

It is recommended that an external bootstrap

diode be added when the input voltage is no

greater than 5V or the 5V rail is available in the

system. This helps improve the efficiency of the

regulator. The bootstrap diode can be a low

cost one such as IN4148 or BAT54.

MPQ4460

Figure 3—External Bootstrap Diode

This diode is also recommended for high duty

cycle operation (when VOUT /VIN >65%) or low

VIN (<5Vin) applications.

At no load or light load, the converter may

operate in pulse skipping mode in order to

maintain the output voltage in regulation. Thus

there is less time to refresh the BS voltage. In

order to have enough gate voltage under such

operating conditions, the difference of VIN –VOUT

should be greater than 3V. For example, if the

VOUT is set to 3.3V, the VIN needs to be higher

than 3.3V+3V=6.3V to maintain enough BS

voltage at no load or light load. To meet this

requirement, EN pin can be used to program

the input UVLO voltage to Vout+3V.

MPQ4460 Datasheet(PDF) 15 Page - Monolithic Power Systems