ACT8600 datasheet(44/51 Pages) ACTIVE-SEMI

44 / 51 page

ACT8600

Rev 3, 15-Nov-12

Innovative Power

ActivePMU

TM and ActivePathTM are trademarks of Active-Semi.

2CTM is a trademark of NXP.

- 44 -

www.active-semi.com

General Description

The charger features an advanced battery charger

that incorporates the patent-pending ActivePathTM

architecture for system power selection. This

combination of circuits provides a complete,

advanced

battery-management

system

that

automatically selects the best available input

supply, manages charge current to ensure system

power availability, and provides a complete, high-

accuracy (±0.5%), thermally regulated, full-featured

single-cell linear Li+ Charger that can withstand

input voltages of up to 12V at CHGIN.

ActivePath

TM Architecture

The ActivePathTM architecture performs three

important functions:

1) System Configuration Optimization

2) Input Protection

3) Battery-Management

System Configuration Optimization

The ActivePath circuitry monitors the state of the

input supply, the battery, and the system, and

automatically reconfigures itself to optimize the

power system. If a valid input supply at either

CHGIN or VBUS is present, ActivePath powers the

system from the input while charging the battery in

parallel. Of the two possible charging sources,

CHGIN is the preferred one over VBUS to allow the

battery to charge as quickly as possible, while

supplying the system. If a valid input supply is not

present, ActivePath powers the system from the

battery. If the input is present and the system

current requirement exceeds the capability of the

input supply, ActivePath allows system power to be

drawn from both the battery and the input supply.

Note that the battery will not be charged from VBUS

pin when VBUS is supplied by the 5VIN pin

(through Q1).

Input Protection for CHGIN

Input Over-Voltage Protection

The ActivePathTM circuitry features input over-

voltage protection circuitry for CHGIN. This circuitry

disables charging when the input voltage exceeds

the voltage set by OVPSET[ ], but stands off the

input voltage in order to protect the system. Note

that the adjustable OVP threshold is intended to

provide the charge cycle with adjustable immunity

against upward voltage transients on the input, and

is not intended to allow continuous charging with

input voltages above the charger's normal operating

voltage range. Independent of the OVPSET[ ]

setting, the charge cycle is not allowed to continue

until the input voltage falls back into the charger's

normal operating voltage range (i.e. below 6.0V).

In an input over-voltage condition this circuit limits

VVSYS to 4.6V, protecting any circuitry connected to

VVSYS from the over-voltage condition, which may

exceed this circuitry's voltage capability. This circuit

is capable of withstanding input voltages of up to

12V.

Table 7:

Input Over-Voltage Protection Setting

Input Supply Overload Protection

The ActivePathTM circuitry monitors and limits the

total current drawn from the input supply to a value

set

the

CHGIN/VBUS

configuration

and

CHGLEV inputs, as well as the resistor connected

to ISET. When charging from VBUS pin, the input

current is limited to either 75mA, when CHGLEV is

driven to a logic-low, or 450mA, when CHGLEV is

driven to a logic-high. When charging from CHGIN,

the input current is limited to 2.25A, typically.

Input Under Voltage Lockout

If the input voltage applied to CHGIN falls below

3.5V (typ), an input under-voltage condition is

detected and the charger is disabled. Once an input

under-voltage condition is detected, a new charge

cycle will initiate when the input exceeds the under-

voltage threshold by at least 500mV.

Battery Management

The ACT8600 features a full-featured, intelligent

charger for Lithium-based cells, and was designed

specifically to provide a complete charging solution

with minimum system design effort.

The core of the charger is a CC/CV (Constant-

Current/Constant-Voltage),

linear-mode

charge

controller. This controller incorporates current and

voltage sense circuitry, an internal 70mΩ power

MOSFET,

thermal-regulation

circuitry,

full-

featured state-machine that implements charge

control and safety features, and circuitry that

eliminates the reverse blocking diode required by

conventional charger designs.

Single-Cell Li+ ActivePath

TM Charger

OVPSET[0]

OVP THRESHOLD

6.6V

7.0V

ACT8600 Datasheet(PDF) 44 Page - Active-Semi, Inc

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