MP5512 – 18V, 4.5A ENERGY STORAGE AND MANAGEMENT UNIT

MP5512 Rev. 1.1

www.MonolithicPower.com

13

4/27/2016

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© 2016 MPS. All Rights Reserved.

OPERATION

The MP5512 is an energy storage and

management unit in a 4mm×5mm 28-pin QFN

package. It provides a compact and efficient

energy management solution for typical solid-

state–drive or hard-disk drive applications.

MPS’ patented lossless-energy storage and

release-management

circuits

use

a

bi-

directional buck/boost converter to achieve

optimal energy transfer and provide a cost-

effective energy-storage solution.

MP5512’s

built-in

boost-mode

converter

charges the storage bulk capacitor to a

programmed voltage when the system is

powered up. In case of an input power failure,

MP5512 flags the power failure, disconnects

the input power and transfers the energy from

the storage capacitor to the bus capacitor via

the built-in buck mode converter. This supports

SSD system data backup. The buck converter

works in 100% duty-cycle operation to fully

deplete the stored energy.

Start-Up

When the VIN power and enable signal are

higher than their UVLO, MP5512 starts up with

the programmed power-on-reset delay time.

Initially, the hot-swap MOSFET from VIN to VB

is on and the bus capacitor is charged from 0 to

VIN

EN=ENCH

Storage-Voltage

Power-On-Reset Delay Time

Target storage voltage

BUS Voltage

Charge Up VB with dv/dt Control

Boost for Storage

DVDT

Boost-Delay Time

Pre-Charge

Figure 2: Charging Process

PFI is set to high to indicate the power condition.

If PFI is high and dv/dt voltage is saturated, the

charge circuit is enabled to charge storage

capacitors on STRG (after about 1.8ms delay

time). The storage voltage is charged with

450mA trickle current during the pre-charge

period. Once the storage voltage is close to VB

voltage, the boost-switching circuit initiates and

the storage voltage is boosted to the target

voltage (see Figure 2).

Storage Voltage

After the start-up period, the internal boost

converter automatically regulates the storage

voltage to the set value. The MP5512 uses

burst mode to minimize the converter’s power

loss. When the storage voltage drops below the

set voltage, burst mode initiates and charges

the storage capacitor. During the burst period,

the current limit and the low-side MOSFET

control the boost. When the power MOSFET

turns on, the inductor current increases until it

reaches its current limit. After hitting the current

limit, the power MOSFET turns off for the set

minimum off time. If the feedback voltage

remains below the 0.8V internal reference at

the end of the minimum off time, the power

MOSFET turns on again. Otherwise, the

MP5512 waits until the voltage drops below the

reference threshold before turning on. In boost

mode, the high-side MOSFET won’t turn on and

the inductor current conducts through the body-

diode of HS-FET.

The boost-current limit is programmed by the

ICH resistor. The programmed boost-switching

current limit can be estimated with:

7

10

)

(

35

)

(









L

V

k

R

A

I

IN

ICH

CH

and L is the boost inductor.

If the ICH is floating, the boost-peak current

limit is about 960mA (for typical 12V input and

10uH inductor applications).

MP5512 has over-voltage protection for STRG

the

low-side

MOSFET