MP2633 – 1.5A SINGLE CELL SWITCH MODE BATTERY CHARGER

MP2633 Rev. 1.05

www.MonolithicPower.com

23

4/19/2013

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OPERATION

INTRODUCTION

The MP2633 is a highly-integrated, synchronous,

switching charger with bi-directional operation for

a boost function that can step-up the battery

voltage to power the system. Depending on the

VIN value, it operates in one of three modes:

charge mode, boost mode and sleep mode. In

charge mode, the MP2633 supports a precision

Li-ion or Li-polymer charging system for single-

cell applications. In boost mode, MP2633 boosts

voltage systems. In sleep mode, the MP2633

stops charging or boosting and operates at a low

current from the input or the battery to reduce

power consumption when the IC isn’t operating.

The MP2633 monitors VIN to allow smooth

transition between different modes of operation.

CHARGE MODE OPERATION

Charge Cycle (Trickle Charge CC

Charge CV Charge)

In charge mode, the MP2633 has five control

loops to regulate the input current, input voltage,

charge current, charge voltage, and device

junction temperature. It charges the battery in

three phases: trickle current (TC), constant

current (CC), and constant voltage (CV). While

charging, all four loops are active but only one

determines the IC behavior. Figure 11(a) shows

a typical battery charge profile. The charger stays

in TC charge mode until the battery voltage

reaches a TC-to-CC threshold. Otherwise the

charger enters CC charge mode. When the

battery voltage rises to the CV-mode threshold,

the charger operates in constant voltage mode.

Figure 11 (b) shows a typical charge profile when

the input-current-limit loop dominates during the

CC charge mode, and in this case the charge

current exceeds the input current, resulting in

faster charging than a traditional linear solution

that is well-suited for USB applications.

Auto-Recharge

Once the battery charge cycle completes, the

charger remains off. During this process, the

system load may consume battery power, or the

battery may self discharge. To ensure that the

battery will not go into depletion, a new charge

cycle automatically begins when the battery

Trickle charge

TC>>>CC

Threshold

CC>>>CV

Threshold

CC charge

CV charge

Charge Full

Trickle

Charge

Current

Constant

Charge

Current

a) Without input current limit

Trickle charge

TC>>>CC

Threshold

CC>>>CV

Threshold

CC charge

CV charge

Charge Full

Trickle

Charge

Current

Input

Current

Limit

Constant

Charge

Current

b) With input current limit

Figure 11: Typical Battery Charginge Profile

voltage falls below the auto-recharge threshold

and the input power is present. The timer resets

when the auto-recharge cycle begins.

During the off state after the battery is fully

charged, if the input power re-starts or the EN

signal refreshes, the charge cycle will start and

the timer will reset no matter what the battery

voltage is.

Battery Over-Voltage Protection

The MP2633 has battery over-voltage protection.

If the battery voltage exceeds the battery over-

voltage threshold, (103.3% of the battery-full

voltage), charging is disabled. Under this

condition, an internal current source draws a

current from the BATT pin to decrease the

battery voltage and protect the battery.

Timer Operation in Charge Mode

The MP2633 uses an internal timer to terminate

the charging. The timer remains active during the

charging process. An external capacitor between

TMR and GND programs the charge cycle

duration.