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AAT3691

DATA SHEET

Dual Input 1.6A Linear Charger with 28V OVP in a 3x4 TDFN Package

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201894B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 27, 2012

Functional Description

The AAT3691 is a high performance battery charger

designed to charge single cell Lithium Ion or Polymer

batteries with up to 1600mA charging current from an

adaptor (ADP) power source, or with up to 500mA

charging current from an USB power source. The

AAT3691 is a stand-alone charging solution, with just a

few external component required for complete function-

ality. Both input paths include a fast turn-off over-volt-

age protection (OVP) circuit with voltage up to +28V and

an under-voltage lockout level of 3.0V.

The AAT3691 automatically selects the charging source

from USB or ADP according to ADP and USB voltage. The

ADP path is always the high priority charging path when

ADP voltage is higher than 4.5V. The charging current is

determined by the selected charging path and its exter-

USB charging uses an automatic charge reduction loop

control allow battery charging with limited available cur-

rent from a USB port while maintaining the regulated

port voltage. This system assures that the battery

charge function will not overload a USB port while charg-

ing if other system demands also share power with the

respective port supply.

During adapter charging, high set charging current or

high ambient operating temperature may cause the

special digital thermal loop control system is employed

to maximize charging current by dynamically decreasing

the battery charging current.

Thermal protection shuts down the AAT3691's charging

function when internal dissipation becomes excessive,

while OVP function still works. The junction over-temper-

ature threshold is 140°C with 15°C of hysteresis. Once

an over-temperature condition is removed, the charging

function automatically recovers.

The status monitor output pin (STAT) is designed to indi-

cate the battery charge status with open-drain structure

by directly driving one external LED.

Battery Charging Operation

Regardless of which charge input function is selected

(adapter input or USB input), the AAT3691 has three

basic modes for the battery charge cycle: precondition-

ing (trickle) charge, constant current/fast charge, and

constant voltage charge. When no automatic charge

reduction mode or digital thermal loop is triggered, the

charge profile is controlled as shown in Figure 1.

Functional Block Diagram

Charge

Control

Current

Compare

Current

Compare

Reverse Blocking

BAT

UVLO

Over-Temp.

Protect

GND

STAT

USB

EN

CV/Precharge

USBCH

USBSET

Charge

Status

ADPSET

NOBAT

Reverse Blocking

OVP Sense

and Control

OVP Sense

and Control

ADPCH

ADP

OVP Switch

IC