MP2625

– SINGLE CELL SWITCHING CHARGER WITH POWER PATH CONTROL

MP2625 Rev. 1.12

www.MonolithicPower.com

14

10/29/2013

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© 2013 MPS. All Rights Reserved.

Introduction

The MP2625 is a switching charger IC, with

integrated smart power path management for

powering the system and charging a single cell

battery simultaneously and independently.

The MP2625 includes a high-voltage (up to 14V)

input DC-DC step down converter for wide range

of DC sources and USB inputs. It has precision

average input current limit to make maximum use

of the allowable input power. This feature allows

fast charging when powering from an USB port,

and ensures the input current never exceeds the

input power specification especially when the

input power comes from a USB port. Additionally,

the

input

current

limit

threshold

can

be

programmed by logic inputs or a resistor to

ground from the ILIM pin.

The MP2625 implements an on-chip 4

0mΩ

MOSFET which works as a full-featured linear

charger

with

trickle

charge,

high

accuracy

constant current and constant voltage charge,

charge termination, auto recharge, NTC monitor,

built-in timer control, charge status indication,

and thermal protection. The charge current can

be

programmed

by

an

external

resistor

connected from the ISET pin to AGND. The IC

limits

the

charge

current

when

the

die

temperature exceeds 120°C.

The 4

0mΩ MOSFET works as an ideal diode to

connecting the battery to the system load when

the input power is not enough to power the

system load. When the input is removed, the

40m

Ω MOSFET is turned on allowing the battery

to power up the system.

With smart power path management, the system

load is satisfied in priority then the remaining

current is used to charge the battery. The

MP2625 will reduce charging current or even use

power from the battery to satisfy the system load

when its demand is over the input power

capacity.

Figure 1 shows the function block diagram of

MP2625.

DC-DC Step Down Converter

The DC-DC converter is a 1.6MHz constant

frequency

step-down

switching

regulator

to

provide the input power to the SYS, which drives

the combination of the system load and battery

charger. The regulator contains input current

measurement and control scheme to ensure the

average input current remains below the level

programmed via ILIM pin or logic inputs M0&M1.

This meets the adapter capacity limit or stays in

compliance with USB specification.

When the input voltage is higher than UVLO and

310mV higher than the battery voltage, input

voltage OK signal is active (ACOK

——————

turns low) and

the DC-DC converter soft-starts. If the input

power is sufficient to supply the combination of

the system load and battery charger, and the

input current limit loop is not triggered. The

above the battery voltage to minimize the power

loss of the battery charger during fast charging.

the system immediately even when a drained

battery is inserted to be charged. Figure 2 shows

System voltage can also be regulated to any

value between 3.6V to 4.4V by using a resistor

divider on the SYSFB pin. This is shown as R6

and R7 in Figure 9. If the SYSFB is left floating,

regulated as Figure 2.

The converter adopts fixed off-time control to

extend the duty cycle (close to 100%) when the

4.4V

4.2V

3.6V

4.2V

3.4V

200mV

Figure 2

— SYS Regulation Output