AAT3687IWP-4.2-1-T1 - Skyworks Solutions, Inc.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

General Description

The AAT3687 BatteryManager is a highly integrated sin-

gle-cell lithium-ion/polymer battery charger IC designed

to operate with AC adapter inputs. It requires a minimum

number of external components. The AAT3687 precisely

regulates battery charge voltage and current for 4.2V

lithium-ion/polymer battery cells. Adapter charge current

rates can be programmed up to 1.5A. An active thermal

management system regulates the fast charge constant

current for all ambient temperature and input vs. output

voltage conditions.

Battery temperature and charge state are fully moni-

tored for fault conditions. In the event of an over-voltage

or over-temperature failure, the device will automati-

cally shut down, thus protecting the charging device,

control system, and the battery under charge. Status

monitor output pins are provided to indicate the battery

charge status by directly driving two external LEDs. A

serial interface output is available to report 12 various

charging status states to a microcontroller.

The AAT3687 is available in a Pb-free, thermally-enhanced,

space-saving 12-pin TDFN 3x3mm package and is rated

over the -40°C to +85°C temperature range.

Features

• Input Voltage Range: 4.0V to 5.5V

• Up to 1.5A Charging Current

• Adapter Present Indicator (ADPP#)

• High Level of Integration with Internal:

▪ Charging Device

▪ Reverse Blocking Diode

▪ Current Sensing

• Active Thermal Loop Charge Reduction

• Automatic Recharge Sequencing

• Battery Temperature Monitoring

• Full Battery Charge Auto Turn-Off / Sleep Mode

• Over-Voltage, Over-Current, and Over-Temperature

Protection

• Power On Reset and Soft Start

• Serial Interface Status Report

• 12-Pin 3x3mm TDFN Package

• -40°C to +85°C Temperature Range

Applications

• Cellular Telephones

• Digital Still Cameras

• Hand Held PCs

• MP3 Players

• Personal Data Assistants (PDAs)

• Other Lithium-Ion/Polymer Battery-Powered Devices

Typical Application

AAT3687

COUT

10μF

BATT-

TEMP

Battery

Pack

ADP

ADPSET

GND

BAT

BATT+

RSET

RB1 RB2

CIN

10μF

0.1μF

dapter

STAT1

LED1

LED2

STAT2

DATA

Serial Interface

ENEnable

ADPP#

Adapter

Present

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

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AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Pin Descriptions

Pin # Name Type Function

1 BAT Out Battery charging and sensing.

2 ADP In Adapter input.

3 GND Ground Ground connection.

4EN In

AAT3687: Enable pin. Logic high enables the IC.

AAT3687-2: Enable pin. Logic high enables the IC. EN tied to internal 4M pull-up resistor to ADP.

5 ADPP# Out Adapter present indicator. This pin is open drain until ADP pin reaches threshold.

6 TS In/Out Connect to 10k NTC thermistor.

7 DATA Out Status report to microcontroller via serial interface: open drain.

8 STAT2 Out Battery charge status indicator pin to drive an LED: active low, open drain.

9 STAT1 Out Battery charge status indicator pin to drive an LED: active low, open drain.

10 CT In/Out

Timing capacitor to adjust internal watchdog timer. Set maximum charge time for adapter pow-

ered trickle, CC, and CV charge modes. If timing function is not needed, terminate this pin to

ground.

11 N/C No connection.

12 ADPSET In/Out Use resistor at this pin to set adapter charging current.

EP Exposed paddle (bottom); connect to GND directly beneath package.

Pin Configuration

TDFN33-12

(Top View)

BAT

ADP

GND

DPP#

ADPSET

N/C

STAT1

STAT2

DATA

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687 Feature Options

Product Trickle Charge

Internal Pull-Up

Resistor on EN Pin

Can Leave

TS Pin Open

AAT3687 Yes No No

AAT3687-1 Yes Yes Yes

Absolute Maximum Ratings1

Symbol Description Value Units

VPADP Input Voltage, <30ms, Duty Cycle <10% -0.3 to 7.0

VVPADP Input Voltage, Continuous -0.3 to 6.0

VNBAT, TS, ADPSET, ADPP#, DATA, CT, EN, STAT1, STAT2 -0.3 to VP + 0.3

TJOperating Junction Temperature Range -40 to 150 °C

TLEAD Maximum Soldering Temperature (at leads) 300

Thermal Information

Symbol Description Value Units

JA Maximum Thermal Resistance250 °C/W

PDMaximum Power Dissipation 2.0 W

1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions

specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.

2. Mounted on an FR4 board.

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Electrical Characteristics1

VADP = 5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.

Symbol Description Conditions Min Typ Max Units

Operation

ADP Adapter Voltage Range 4.0 5.5 V

VADPP Adapter Present Threshold Voltage 3.0 V

VUVLO

Under-Voltage Lockout (UVLO) Rising Edge 3.0 V

UVLO Hysteresis 150 mV

IOP Operating Current Charge Current = 100mA 0.75 1.5 mA

ISLEEP Sleep Mode Current AAT3687: VBAT = 4.25V 0.3 1.0 μA

AAT3687-1: VBAT = 4.25V 1 3

ILeakage Reverse Leakage Current from BAT Pin VBAT = 4V, ADP Pin Open 1.0 μA

Voltage Regulation

VBAT_EOC1End of Charge Voltage Accuracy 4.158 4.20 4.242 V

VCH/VCH Output Charge Voltage Tolerance 0.5 %

VMIN Preconditioning Voltage Threshold 2.8 3.0 3.15 V

VRCH Battery Recharge Voltage Threshold VBAT_EOC -

0.1 V

Current Regulation

ICH Charge Current 100 1500 mA

ICH/ICH Charge Current Regulation Tolerance 10 %

VADPSET ADPSET Pin Voltage CC Mode 2.0 V

KIA Current Set Factor: ICH/IADPSET 4000

Charging Devices

RDS(ON)

Adapter Charging Transistor

On Resistance VIN = 5.5V 0.2 0.25 0.35 

1. The AAT3687 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -40°C to +85°C temperature range is guaranteed by design.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

Electrical Characteristics1

VADP = 5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.

Symbol Description Conditions Min Typ Max Units

Logic Control / Protection

VEN(H) Input High Threshold 1.6 V

VEN(L) Input Low Threshold 0.4 V

IEN(H) EN Input Current AAT3687-1 Only; VEN = 5V 10 μA

VADPP# Output Low Voltage ADPP# Pin Sinks 500μA 0.4 V

Preconditioning Plus Constant Current

Mode Time Out CT = 0.1μF, VADP = 5.5V 3.0 Hours

TPPreconditioning Time Out CT = 0.1μF, VADP = 5.5V 25 Minutes

TVConstant Voltage Mode Time Out CT = 0.1μF, VADP = 5.5V 3.0 Hours

VSTAT Output Low Voltage STAT Pin Sinks 4mA 0.4 V

ISTAT STAT Pin Current Sink Capability 8.0 mA

VOVP Over-Voltage Protection Threshold 4.4 V

ITK/ICHG Pre-Charge Current 10 %

ITERM/ICHG Charge Termination Threshold Current 7.5 %

ITS Current Source from TS Pin 70 80 90 μA

TS1 TS Hot Temperature Fault Threshold 310 330 350 mV

Hysteresis 15

TS2 TS Cold Temperature Fault Threshold 2.2 2.3 2.4 V

Hysteresis 10 mV

IDATA DATA Pin Sink Current DATA Pin is Active Low State 3 mA

IADPP# ADPP# Current Sink ADPP# Pin is Active Low State 8 mA

VDATA(H) Input High Threshold 1.6 V

VDATA(L) Input Low Threshold 0.4 V

SQPULSE Status Request Pulse Width Status Request 200 ns

tPERIOD System Clock Period 50 μs

fDATA Data Output Frequency 20 kHz

TREG Thermal Loop Regulation 90 °C

TLOOP_IN Thermal Loop Entering Threshold 110 °C

TLOOP_OUT Thermal Loop Exiting Threshold 85 °C

TOVSD Over-Temperature Shutdown Threshold 145 °C

1. The AAT3687 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -40°C to +85°C temperature range is guaranteed by design.

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Typical Characteristics

Charge Current vs. RSET

RSET (kΩ

)

ICH (mA)

100

1000

10000

1 10 100

Battery Voltage vs. Supply Voltage

Supply Voltage (V)

VBAT (V)

4.158

4.179

4.200

4.221

4.242

4.5 4.75 5.0 5.25 5.5

End of Charge Voltage Regulation

vs. Temperature

Temperature (°

VBAT_EOC (V)

4.158

4.179

4.200

4.221

4.242

-50 -25 0 25 50 75 100

Preconditioning Threshold

Voltage vs. Temperature

Temperature (°

VMIN (V)

2.95

2.96

2.97

2.98

2.99

3.00

3.01

3.02

3.03

3.04

3.05

-50 -25 0 25 50 75 100

Pre-Charge Current vs. Temperature

(ADPSET = 8.06kΩ

)

Temperature (

ITK (mA)

100

110

120

-50 -25 0 25 50 75 100

Charge Current vs. Temperature

(ADPSET = 8.06kΩ

)

Temperature (

ICH (mA)

900

920

940

960

980

1000

1020

1040

1060

1080

1100

-50 -25 0 25 50 75 100

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

Typical Characteristics

Charge Current vs. Battery Voltage

(ADPSET = 8.06kΩ

; VIN = 5.0V)

Battery Voltage (V)

ICH (A)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2.5 2.9 3.3 3.7 4.1 4.5

Fast Charge Current vs. Supply Voltage

(ADPSET = 8.06kΩ

)

Supply Voltage (V)

ICH (mA)

200

400

600

800

1000

1200

4.0 4.5 5.0 5.5 6.

VBAT = 3.3V

VBAT = 3.5V

VBAT = 3.9V

VIH vs. Supply Voltage

EN Pin (Rising)

Supply Voltage (V)

VIH (V)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0

-40°C +25°C

+85°C

VIL vs. Supply Voltage

EN Pin (Falling)

Supply Voltage (V)

VIH (V)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0

-40°C +25°C

+85°C

Operating Current vs. ADPSET Resistor

ADPSET Resistor (kΩ

)

IOP (mA)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

1 10 100 1000

Pre-Conditioning

Constant Current

Counter Timeout vs. Temperature

(CT = 0.1µF)

Temperature (°

Counter Timeout (%)

-10

-8

-6

-4

-2

-50 -25 0 25 50 75 100

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Typical Characteristics

CT Pin Capacitance vs. Counter Timeout

Time (hours)

Capacitance (μ

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0246810

Precondition Timeout

Precondition + Constant Current Timeout

or Constant Voltage Timeout

Temperature Sense Output Current

vs. Temperature

Temperature (°

TS Pin Current (

-50 -25 0 25 50 75 10

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

Functional Description

The AAT3687 is a highly integrated single-cell lithium-

ion/polymer battery charger IC designed to operate with

standard AC adapter input sources, while requiring a

minimum number of external components. The AAT3687

precisely regulates battery charge voltage and current

for 4.2V lithium-ion/polymer battery cells.

The adapter charge input constant current level can be

programmed up to 1.5A for rapid charging applications.

The AAT3687 is rated for operation from -40°C to

+85°C. In the event of operating ambient temperatures

exceeding the power dissipation abilities of the device

package for a given constant current charge level, the

charge control will enter into thermal regulation. When

the system thermal regulation becomes active, the pro-

grammed constant current charge amplitude will be

automatically reduced to a safe level for the current

operating condition. Should the ambient operating tem-

perature drop below the thermal loop threshold, the

system will automatically resume charging at the full

programmed constant current level. This intelligent ther-

mal management system permits the AAT3687 to oper-

ate and safely charge a battery cell over a wide range of

ambient conditions while maximizing the greatest pos-

sible charge current for the given set of conditions.

Status monitor output pins are provided to indicate the

battery charge state by directly driving two external

LEDs. A serial interface output is also available to report

any one of 12 distinct charge states to the system micro-

controller.

Battery temperature and charge state are fully monitored

for fault conditions. In the event of an over-voltage or

over-temperature failure, the device will automatically

shut down, thus protecting the charging device, control

system, and the battery under charge. In addition to

internal charge controller thermal protection, the AAT3687

also provides a temperature sense feedback function (TS

pin) from the battery to shut down the device in the

event the battery exceeds its own thermal limit during

charging. All fault events are reported to the user either

by the simple status LEDs or via the DATA pin function.

Functional Block Diagram

Charge

Control

Reverse Blocking

CV/

Precharge1

Constant

Current

Compare

ADP

BAT

DPSET

UVLO

Over-

Temperature

Protection

Charge

Status

STAT2

STAT1 TS

Window

Comparator

80μA

4.2V

Serial

Data

DATA Watchdog

Timer CT

Voltage

Sense

ADPP#

GND

IC enable

1. Precharge applies to AAT3687 and AAT3687-1 only.

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Charging Operation

The AAT3687 has four basic modes for the battery charge

cycle: pre-conditioning / trickle charge; constant current

/ fast charge; constant voltage; and end of charge (see

Figure 1).

Battery Preconditioning

Before the start of charging, the AAT3687 checks sev-

eral conditions in order to assure a safe charging envi-

ronment. The input supply must be above the minimum

operating voltage, or under-voltage lockout threshold

(VUVLO), for the charging sequence to begin. Also, the cell

temperature, as reported by a thermistor connected to

the TS pin from the battery, must be within the proper

window for safe charging. When these conditions have

been met and a battery is connected to the BAT pin, the

AAT3687 checks the state of the battery. If the cell volt-

age is below the preconditioning voltage threshold (VMIN),

the charge control begins preconditioning the cell.

The battery preconditioning trickle charge current is

equal to the fast charge constant current divided by 10.

For example, if the programmed fast charge current is

1.5A, then the preconditioning mode (trickle charge)

current will be 150mA. Cell preconditioning is a safety

precaution for deeply discharged battery cells and also

aids in limiting power dissipation in the pass transistor

when the voltage across the device is at the greatest

potential.

Fast Charge / Constant Current Charging

Battery cell preconditioning continues until the voltage

on the BAT pin exceeds the preconditioning voltage

threshold (VMIN). At this point, the AAT3687 begins the

constant current fast charging phase. The fast charge

constant current (ICC) amplitude is programmed by the

user via the RSET resistor. The AAT3687 remains in the

constant current charge mode until the battery reaches

the voltage regulation point, VBAT

Constant Voltage Charging

The system transitions to a constant voltage charging

mode when the battery voltage reaches the output

charge regulation threshold (VBAT) during the constant

current fast charge phase. The regulation voltage level

is factory programmed to 4.2V (±1%). Charge current

in the constant voltage mode drops as the battery cell

under charge reaches its maximum capacity.

End of Charge Cycle Termination

and Recharge Sequence

When the charge current drops to 7.5% of the pro-

grammed fast charge current level in the constant volt-

age mode, the device terminates charging and goes into

a sleep state. The charger will remain in a sleep state

until the battery voltage decreases to a level below the

battery recharge voltage threshold (VRCH).

When the input supply is disconnected, the charger will

automatically transition into a power-saving sleep mode.

Only consuming an ultra-low 0.3μA in sleep mode (1μA

for AAT3687-1), the AAT3687 minimizes battery drain

when it is not charging. This feature is particularly useful

in applications where the input supply level may fall

below the battery charge or under-voltage lockout level.

In such cases where the AAT3687 input voltage drops,

the device will enter sleep mode and automatically

resume charging once the input supply has recovered

from the fault condition.

Constant Current

Charge Phase

Constant Voltage

Charge Phase

Preconditioning

Trickle Charge

Phase

Charge Complete Voltage

Constant Current Mode

Voltage Threshold

Regulated Current

Trickle Charge and

Termination Threshold

I = CC / 10

I = Max CC

Figure 1: Current vs. Voltage Profile During Charging Phases.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

System Operation Flow Chart

Yes Yes

Yes

Set

Enable

Timing

Expire

Yes

(AAT3687)

TERM

Yes

BAT_EOC

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Application Information

Adapter Power Input

Constant current charge levels up to 1.5A may be pro-

grammed by the user when powered from a sufficient

input power source. The AAT3687 will operate from the

adapter input over a 4.0V to 5.5V range.

The constant current fast charge current for the adapter

input is set by the RSET resistor connected between the

ADPSET and ground. Refer to Table 1 for recommended

RSET values for a desired constant current charge level.

The presence of voltage on the adapter input is indicated

by the ADPP# pin function. This indicator pin uses an

internal open drain device that will pull the ADPP# pin

low when voltage is detected on the ADP pin. The pre-

cise charging function of the AAT3687 may be read from

the DATA pin and/or status LEDs. Please refer to the

Battery Charge Status Indication discussion for further

details on data reporting.

Thermal Loop Control

Due to the integrated nature of the linear charging con-

trol pass device for the adapter input, a special thermal

loop control system has been employed to maximize

charging current under all operating conditions. The

thermal management system measures the internal cir-

cuit die temperature and reduces the fast charge current

when the device exceeds a preset internal temperature

control threshold. Once the thermal loop control becomes

active, the fast charge current is initially reduced by a

factor of 0.44.

The initial thermal loop current can be estimated by the

following equation:

Eq. 1: ITLOOP = ICC · 0.44

The thermal loop control re-evaluates the circuit die tem-

perature in 330ms intervals and adjusts the fast charge

current back up in small steps to the full fast charge cur-

rent level or until an equilibrium current is discovered

and maximized for the given ambient temperature condi-

tion. The thermal loop controls the system charge level;

therefore, the AAT3687 will always provide the highest

level of constant current in the fast charge mode possible

for any given ambient temperature condition.

Adapter Input Charge Inhibit and Resume

The AAT3687 has a UVLO and power on reset feature so

that the charger will suspend charging and shut down if

the input supply to the adapter pin drops below the

UVLO threshold. When power is re-applied to the adapt-

er pin or the UVLO conditions recovers, the system

charge control will assess the state of charge on the bat-

tery cell and will automatically resume charging in the

appropriate mode for the condition of the battery.

Enable / Disable

The AAT3687 provides an enable function to control the

charger IC on and off. The enable (EN) pin is active high.

When pulled to a logic low level, the AAT3687 will be

shut down and forced into the sleep state. Charging will

be halted regardless of the battery voltage or charging

state. When the device is re-enabled, the charge control

circuit will automatically reset and resume charging

functions with the appropriate charging mode based on

the battery charge state and measured cell voltage on

the BAT pin.

Programming Charge Current

The fast charge constant current charge level is user

programmed with a set resistor placed between the

ADPSET pin and ground. The accuracy of the fast charge,

as well as the preconditioning trickle charge current, is

dominated by the tolerance of the set resistor used. For

this reason, a 1% tolerance metal film resistor is recom-

mended for the set resistor function.

Fast charge constant current levels from 50mA to 1.5A

can be set by selecting the appropriate resistor value

from Table 1.

ICC

ADP

RSET (k)I

ADP

RSET (k)

50 N/A 800 10.2

75 N/A 900 9.09

100 84.5 1000 8.06

200 43.2 1100 7.32

300 28.0 1200 6.65

400 21.0 1300 6.04

500 16.9 1400 5.62

600 13.3 1500 5.36

700 11.5

Table 1: Recommended RSET Values.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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

201890B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 26, 2012

RSET (kΩ

)

ICH (mA)

100

1000

10000

1 10 100

Figure 2: IFASTCHARGE vs. RSET.

Protection Circuitry

Programmable Watchdog Timer

The AAT3687 contains a watchdog timing circuit to shut

down charging functions in the event of a defective bat-

tery cell not accepting a charge over a preset period of

time. Typically, a 0.1μF ceramic capacitor is connected

between the CT pin and ground. When a 0.1μF ceramic

capacitor is used, the device will time out a shutdown

condition if the trickle charge mode exceeds 25 minutes

and a combined trickle charge plus fast charge mode of

3 hours. When the device transitions to the constant

voltage mode, the timing counter is reset and will time

out after an additional 3 hours if the charge current does

not drop to the charge termination level.

Mode Time

Trickle Charge (TC) Time Out 25 minutes

Trickle Charge (TC) + Fast

Charge (CC) Time Out 3 hours

Constant Voltage (VC) Mode

Time Out 3 hours

Table 2: Summary for a 0.1μF Ceramic Capacitor

Used for the Timing Capacitor.

The CT pin is driven by a constant current source and will

provide a linear response to increases in the timing

capacitor value. Thus, if the timing capacitor were to be

doubled from the nominal 0.1μF value, the time-out

periods would be doubled.

If the programmable watchdog timer function is not

needed, it can be disabled by terminating the CT pin to

ground. The CT pin should not be left floating or un-

terminated, as this will cause errors in the internal tim-

ing control circuit.

The constant current provided to charge the timing

capacitor is very small, and this pin is susceptible to

noise and changes in capacitance value. Therefore, the

timing capacitor should be physically located on the

printed circuit board layout as close as possible to the CT

pin. Since the accuracy of the internal timer is domi-

nated by the capacitance value, a 10% tolerance or bet-

ter ceramic capacitor is recommended. Ceramic capaci-

tor materials, such as X7R and X5R types, are a good

choice for this application.

Over-Voltage Protection

An over-voltage event is defined as a condition where

the voltage on the BAT pin exceeds the maximum bat-

tery charge voltage and is set by the over-voltage pro-

tection threshold (VOVP). If an over-voltage condition

occurs, the AAT3687 charge control will shut down the

device until the voltage on the BAT pin drops below VOVP

The AAT3687 will resume normal charging operation

after the over-voltage condition is removed. During an

over-voltage event, the STAT LEDs will report a system

fault, and the actual fault condition can be read via the

DATA pin signal.

Over-Temperature Shutdown

The AAT3687 has a thermal protection control circuit

which will shut down charging functions should the inter-

nal die temperature exceed the preset thermal limit

threshold.

Battery Temperature Fault Monitoring

In the event of a battery over-temperature condition, the

charge control will turn off the internal pass device and

report a battery temperature fault on the DATA pin func-

tion. The STAT LEDs will also display a system fault. After

the system recovers from a temperature fault, the device

will resume charging operation.

The AAT3687 checks battery temperature before starting

the charge cycle, as well as during all stages of charging.

This is accomplished by monitoring the voltage at the TS

pin. This system is intended for use with negative tem-

perature coefficient thermistors (NTC) which are typically

integrated into the battery package. Most of the com-

monly used NTC thermistors in battery packs are approx-

imately 10k at room temperature (25°C). The TS pin

has been specifically designed to source 80μA of current

to the thermistor. The voltage on the TS pin resulting

from the resistive load should stay within a window of

335mV to 2.32V. If the battery becomes too hot during

charging due to an internal fault or excessive fast charge

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AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

current, the thermistor will heat up and reduce in value,

pulling the TS pin voltage lower than the TS1 threshold,

and the AAT3687 will signal the fault condition.

If the use of the TS pin function is not required by the

system, it should be terminated to ground using a 10k

resistor. Alternatively, on the AAT3687-1 and AAT3687-

2, the TS pin may be left open.

Battery Charge Status Indication

The AAT3687 indicates the status of the battery under

charge with two different systems. First, the device has

two status LED driver outputs. These two LEDs can indi-

cate simple functions such as no battery charge activity,

battery charging, charge complete, and charge fault. The

AAT3687 also provides a bi-directional data reporting

function so that a system microcontroller can interrogate

the DATA pin and read any one of 12 system states.

Status Indicator Display

Simple system charging status states can be displayed

using one or two LEDs in conjunction with the STAT1 and

STAT2 pins on the AAT3687. These two pins are simple

open drain switches used to connect the LED cathodes

to ground. It is not necessary to use both display LEDs

if a user simply wants to have a single lamp to show

“charging” or “not charging.”

This can be accomplished by using the STAT1 pin and a

single LED. Using two LEDs and both STAT pins simply

gives the user more information to the charging states.

Refer to Table 3 for LED display definitions. The LED

anodes should be connected to VADP

The LEDs should be biased with as little current as nec-

essary to create reasonable illumination; therefore, a

ballast resistor should be placed between the LED cath-

odes and the STAT1/2 pins. LED current consumption

will add to the overall thermal power budget for the

device package, hence it is good to keep the LED drive

current to a minimum. 2mA should be sufficient to drive

most low-cost green or red LEDs. It is not recommended

to exceed 8mA for driving an individual status LED.

The required ballast resistor values can be estimated

using the following formulas:

Eq. 2:

ADP -

F(LED)

)

B(STAT1/2)

= I

LED(STAT1/2)

Example:

Eq. 3:

(5.5V

- 2.0

B(STAT1)

= = 1.75kΩ

2mA

Note: Red LED forward voltage (VF) is typically 2.0V @

2mA

Event Description STAT1 STAT2

Charge Disabled or Low Supply Off Off

Charge Enabled Without Battery Flash1Flash1

Battery Charging On Off

Charge Completed Off On

Fault On On

Table 3: LED Status Indicator.

Digital Charge Status Reporting

The AAT3687 has a comprehensive digital data reporting

system by use of the DATA pin feature. This function can

provide detailed information regarding the status of the

charging system. The DATA pin is a bi-directional port

which will read back a series of data pulses when the

system microcontroller asserts a request pulse. This sin-

gle strobe request protocol will invoke one of 12 possible

return pulse counts that the system microcontroller can

look up based on the serial report data listed in Table 4.

N DATA Report Status

1 Chip Over-Temperature Shutdown.

2 Battery Temperature Fault.

3 Over-Voltage Turn Off.

4 Not Used.

5 ADP Watchdog Time-Out in Battery Condition Mode.

6 ADP Battery Condition Mode.

7 ADP Watchdog Time-Out in Constant Current Mode.

ADP Thermal Loop Regulation in Constant Current Mode.

9 ADP Constant Current Mode.

10 ADP Watchdog Time-Out in Constant Voltage Mode.

11 ADP Constant Voltage Mode.

12 ADP End of Charging.

23 Data Report Error.

Table 4: Serial Data Report Table.

1. Flashing rate depends on output capacitance.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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The DATA pin function logic is active low and should nor-

mally be pulled high to VADP

. This data line can also be

pulled high to the same level as the high state for the

logic I/O port on the system microcontroller. In order for

the DATA pin control circuit to generate clean, sharp

edges for the data output, and to maintain the integrity

of the data timing for the system, the pull-up resistor on

the data line should be low enough in value so that the

DATA signal returns to the high state without delay. If

the pull-up resistor is too high, the strobe pulse from the

system microcontroller could exceed the maximum pulse

time and the DATA output control could issue false status

reports. A 1.5k resistor is recommended when pulling

the DATA pin high to 5.0V on the VADP input. If the data

line is pulled high to a voltage level less than 5.0V, the

pull-up resistor can be calculated based on a recom-

mended minimum pull-up current of 3mA. Use the fol-

lowing formula:

Eq. 4:

PULL-UP

≤3mA

Data Timing

The system microcontroller should assert an active low

data request pulse for minimum duration of 200ns; this

is specified by TLO(DATA). Upon sensing the rising edge of

the end of the data request pulse, the AAT3687 status

data control will reply the data word back to the system

microcontroller after a delay specified by the data report

time specification TDATA(RPT). The period of the following

group of data pulses will be specified by TDATA.

AAT3687

Status

Control

1.8V to 5.0V

DATA Pin

PULL_UP

μP GPIO

Port

GPIO

OUT

Figure 3: Data Pin Application Circuit.

Timing Diagram

PULSE

Data

System Reset

System Start

SYNC

LAT

N=1 N=2 N=3

OFF

DATA(RPT)

= T

SYNC

+ T

LAT

< 2.5 P

DATA

OFF

> 2 P

DATA

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AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

Thermal Considerations

The AAT3687 is offered in a 3x3mm TDFN package

which can provide up to 2.0W of power dissipation when

it is properly bonded to a printed circuit board and has

a maximum thermal resistance of 50°C/W. Many consid-

erations should be taken into account when designing

the printed circuit board layout, as well as the placement

of the charger IC package in proximity to other heat

generating devices in a given application design. The

ambient temperature around the charger IC will also

have an effect on the thermal limits of a battery charg-

ing application. The maximum limits that can be expect-

ed for a given ambient condition can be estimated by the

following discussion.

First, the maximum power dissipation for a given situa-

tion should be calculated:

Eq. 5: PD = [(VIN - VBAT) · ICC + (VIN · IOP)]

Where:

PD = Total Power Dissipation by the Device

VIN = Input Voltage Amplitude, VADP

VBAT = Battery Voltage as Seen at the BAT Pin

ICC = Maximum Constant Fast Charge Current

Programmed for the Application

IOP = Quiescent Current Consumed by the Charger IC

for Normal Operation

Next, the maximum operating ambient temperature for

a given application can be estimated based on the ther-

mal resistance of the 3x3mm TDFN package when suf-

ficiently mounted to a PCB layout and the internal ther-

mal loop temperature threshold.

Eq. 6: TA = TJ - (θJA · PD)

Where:

TA = Ambient Temperature in °C

TJ = Maximum Device Junction Temperature Below the

Thermal Loop Threshold

PD = Total Power Dissipation by the Device

JA = Package Thermal Resistance in °C/W

Example:

For an application where the fast charge current for the

adapter mode is set to 1A, VADP = 5.0V and the battery

voltage at 3.6V, what is the maximum ambient tempera-

ture at which the thermal loop will become active?

Given:

VADP = 5.0V

VBAT = 3.6V

ICC = 1A

IOP = 0.75mA

TJ = 110°C

JA = 50°C/W

Using Equation 5, calculate the device power dissipation

for the stated condition:

Eq. 7: PD = (5.0V - 3.6V)(1A) + (5.0V · 0.75mA)

= 1.40375W

The maximum ambient temperature before the AAT3687

thermal loop becomes active can now be calculated

using Equation 6:

Eq. 8: TA = 110°C - (50°C/W · 1.40375W)

= 39.8125°C

Therefore, under the stated conditions for this worst

case power dissipation example, the AAT3687 will enter

the thermal loop and lower the fast charge constant cur-

rent when the ambient operating temperature rises

above 39.8°C.

Capacitor Selection

Input Capacitor

In general, it is good design practice to place a decou-

pling capacitor between the ADP pin and ground. An

input capacitor in the range of 1μF to 22μF is recom-

mended. If the source supply is unregulated, it may be

necessary to increase the capacitance to keep the input

voltage above the under-voltage lockout threshold during

device enable and when battery charging is initiated.

If the AAT3687 adapter input is to be used in a system

with an external power supply source, such as a typical

AC-to-DC wall adapter, then a CIN capacitor in the range

of 10μF should be used. A larger input capacitor in this

application will minimize switching or power transient

effects when the power supply is “hot plugged” in.

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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Output Capacitor

The AAT3687 only requires a 1μF ceramic capacitor on

the BAT pin to maintain circuit stability. This value should

be increased to 10μF or more if the battery connection is

made any distance from the charger output. If the

AAT3687 is to be used in applications where the battery

can be removed from the charger, such as with desktop

charging cradles, an output capacitor greater than 10μF

may be required to prevent the device from cycling on

and off when no battery is present.

Printed Circuit Board

Layout Considerations

For the best results, it is recommended to physically

place the battery pack as close as possible to the

AAT3687 BAT pin. To minimize voltage drops on the PCB,

keep the high current carrying traces adequately wide.

For maximum power dissipation of the AAT3687 3x3mm

TDFN package, the metal substrate should be solder

bonded to the board. It is also recommended to maxi-

mize the substrate contact to the PCB ground plane layer

to further increase local heat dissipation. Refer to the

AAT3687 evaluation board for a good layout example

(see Figures 4 and 5).

AAT3687 Evaluation Board Layout

Figure 4: AAT3687 Evaluation Board Figure 5: AAT3687 Evaluation Board

Component Side Layout. Solder Side Layout.

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AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

AAT3687 Evaluation Board Schematic Diagram

D2 D1

RED

LED

RED

LED

GRN

LED

Open

10μF

10kΩ

8.06kΩ

1.5kΩ

0.1μF

SW1

DAT

123

ON/OFF

TermB3

TermB2

ADP

BAT

GND

ADP

GND

310

BAT

ADPP# 5

DATA 7

STAT2 8

STAT1 9

ADPSET 12

AAT3687

U1 (TDFN33-12)

AAT3687 Evaluation Board Bill of Materials (BOM)

Quantity Description Desig. Footprint Manufacturer Part Number

1 Test Pin DATA PAD Mill-Max 6821-0-0001-00-00-08-0

1Connecting Terminal Block,

2.54mm, 2 Position ADP, GND TBLOK2 Phoenix Contact 277-1274-ND

1Connecting Terminal Block,

2.54mm, 3 Position

BAT,

GND, TS TBLOK3 Phoenix Contact 277-1273-ND

2Capacitor, Ceramic, 10μF 6.3V

10% X5R 0805 C1, C2 0805 Murata GRM219R60J106KE19

1Capacitor, Ceramic, 0.1μF 10%

16V X7R 0603 C3 0603 Murata GRM188R71C104KA01D

2 Typical Red LED, Ultra-Bright D1, D3 1206LED Chicago Miniature Lamp CMD15-21SRC/TR8

1 Typical Green LED D2 1206LED Chicago Miniature Lamp CMD15-21VGC/TR8

1 Header, 3-Pin J1 HEADER2MM-3 Sullins 6821-0-0001-00-00-08-0

1Resistor, 10k, 1/16W 5%

0603 SMD R2 0603 Panasonic/ECG P10KCFCT-ND

1Resistor, 8.06k, 1/16W 1%

0603 SMD R6 0603 Panasonic/ECG P8.06KHCT-ND

4Resistor, 1.5k, 1/16W 5%

0603 SMD

R3, R4,

R5, R7 0603 Panasonic/ECG P1.5KCGCT-ND

1Switch Tact 6mm SPST

H = 5.0mm SW1 Switch ITT Industries/

C&K Div CKN9012-ND

1AAT3687 Lithium-Ion/Polymer

Battery Charger U1 TDFN33-12 Skyworks AAT3687IWP-4.2

AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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Ordering Information

Trickle Charge Package Marking1Part Number (Tape and Reel)2

Yes TDFN33-12 PIXYY AAT3687IWP-4.2-T1

Yes TDFN33-12 TQXYY AAT3687IWP-4.2-1-T1

Skyworks Green™ products are compliant with

all applicable legislation and are halogen-free.

For additional information, refer to Skyworks

Deﬁnition of Green™, document number

SQ04-0074.

Package Information3

TDFN33-12

Top View Bottom View

Detail "A"

Side View

3.00

0.05

Index Area Detail "A"

1.70

0.05

3.00

0.05

0.23

0.05

0.75

0.05

2.40

0.05

0.43

0.05

0.45

0.050.23

0.05

0.1 REF

Pin 1 Indicator

(optional)

C0.3

All dimensions in millimeters.

1. XYY = assembly and date code.

2. Sample stock is generally held on part numbers listed in BOLD.

3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing

process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.

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AAT3687

DATA SHEET

Li-Ion/Polymer Battery Charger

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