MP111 – DYING GASP STORAGE AND RELEASE CONTROL IC

MP111 Rev. 1.0 1

www.MonolithicPower.com

9

4/25/2018

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OPERATION

MP111 is a dying gasp storage and release

control IC. It charges the storage capacitors

from input supply during power start up and

keeps refreshing the storage voltage at a

regulated value during normal operation.

MP111 continuously monitors the input voltage.

Once the input voltage is lower than the

programmed release voltage in case of losing

input power, it releases the charge from the

storage capacitors to input, and keeps the input

voltage regulated to the release voltage for as

long as possible. It allows the system to

respond to input power failure.

Start-Up

During the power start-up, there are two periods

to charge the storage capacitors. In the first

period, the MP111 pre-charges the large

storage capacitors from 0 to nearly VIN with

built-in inrush current limit. Once the storage

voltage is close to the input voltage, the storage

voltage is boosted and regulated at target

voltage.

The BST pin of MP111 should connect to the

DCDC switch node. Only after the DCDC is

enabled, the MP111 will start boosting. Figure 2

shows the charging build-up process of MP111.

Figure 2 – Timing of Charging

Release

MP111 keeps monitoring the input voltage.

Once the input voltage is lower than selected

release voltage in case of losing input power,

MP111 moves the charge from high voltage

storage capacitor to low input voltage capacitor.

The release voltage can be determined by

choosing appropriate input resistance divider.

The maximum LDO release current can be as

high as 2.5A. Until the storage capacitor voltage

is near the input voltage, the input voltage loses

its regulation and reduces further. A conceptual

release process of MP111 is shown in Figure 3.

Vrelease

Vstorage

VIN

GASP

t

Input UVLO of DC/DC converter

Figure 3 – Timing of Releasing

Gasp Indicator

When the FB2 voltage, feedback voltage for the

GASP pin will be pulled high. Connect a resistor

across VIN and GASP can drive GASP high.

the GASP voltage will be internally pulled low.

GASP voltage can be used as communication

indicator signal which states input power

availability.