MP5507E

– 7V, 3A, ENERGY STORAGE AND MANAGEMENT UNIT

MP5507E Rev. 1.0

www.MonolithicPower.com

12

6/29/2016

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

© 2016 MPS. All Rights Reserved.

Storage Voltage

After the storage voltage charges up, the internal

boost converter regulates it to the regulated

voltage automatically. The MP5507E uses burst

mode to minimize the

converter’s power loss.

When the storage voltage drops below the set

voltage, burst mode is initiated and charges the

storage capacitor. During the burst period, the

current limit and the low-side MOSFET (LS-FET)

control the switching. When the LS-FET turns on,

then the inductor current increases until it

reaches the current limit (about 500mA). After

reaching the current limit, the LS-FET turns off

for the set minimum off time. At the end of this

minimum off time, if the feedback voltage

remains below the 0.79V internal reference, the

LS-FET

turns

on

again.

Otherwise,

the

MP5507E waits until the voltage drops below the

threshold before turning on the LS-FET. During

boost mode, the HS-FET is turned off, and the

body diode of the HS-FET conducts the current.

Release

The MP5507E monitors the input voltage and

bus voltage continuously. Once the bus voltage

drops below the release voltage (mostly due to

the input voltage outage), the internal boost

converter stops charging and works in buck-

release mode. In buck mode, the part transfers

energy from the high-voltage storage capacitor

to the low-voltage bus capacitor. Determine the

release voltage by selecting resistor values for

the bus resistor divider.

VB Release

Regulated Voltage

VB

PGB

Figure 4: Release Times

The released buck applies the fixed-frequency

constant-on-time (COT) control and enables a

fast transition between the charge and release

modes. The buck converter works at 100% duty

cycle

until

the

storage

capacitor

voltage

approaches the bus voltage. Then the storage

and VB voltages drop until they reach the

DC/

DC converter’s UVLO threshold (see Figure

4).

Input Current Limit Switch

The input current limit switch controls the input

inrush current of the internal hot-swap MOSFET

to prevent an inrush current from the input to

the VB capacitor. A capacitor connected to

DVDT sets the VB rising soft-start time. Despite

the soft-start process, ILIM can limit the steady-

state current. Connect a resistor between ILIM

and GND to set the current limit.

Reverse-Current Protection

The

hot-swap

circuit

uses

reverse-current

protection to prevent the storage energy from

transferring back to the input when energy is

released from the storage capacitors to the bus.

The hot-swap MOSFET turns on when the input

voltage exceeds the VIN UVLO threshold

during start-up or when the input voltage is

about 0.2V higher than the VB voltage during

VIN power recovery. The hot-swap MOSFET

turns off when the input voltage falls below the

VB voltage during release or when PGB drops.

DVDT

Connect a capacitor across DVDT to program

the soft-start time. Depending on the system

inrush current requirement, different DVDT

capacitors can be selected to program the

inrush current during system start-up.

VIN-to-VB Switch Off Control (DISC)

When DISC is pulled low, the VIN-to-VB

MOSFET switches off directly. If ENCH is high,

the MP5507E enters buck mode once VB drops

to the VB regulation threshold (see Figure 5).

The VIN-to-VB switch cannot turn on until DISC

is high. Pull DISC up to VIN through a 100k

resistor for automatic start-up.