AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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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
CT
GND
TS
BAT
BATT+
RSET
RB1 RB2
CIN
10μF
CT
0.1μF
A
dapter
STAT1
LED1
LED2
STAT2
DATA
Serial Interface
ENEnable
ADPP#
Adapter
Present
+
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Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
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Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
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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 4MΩ 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 10kΩ 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
1
EN
A
DPP#
TS
ADPSET
N/C
CT
STAT1
STAT2
DATA
2
3
4
5
6
12
11
10
9
8
7
AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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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 V
VPADP Input Voltage, Continuous -0.3 to 6.0 V
VNBAT, TS, ADPSET, ADPP#, DATA, CT, EN, STAT1, STAT2 -0.3 to VP + 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads) 300 °C
Thermal Information
Symbol Description Value Units
θJA 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.
AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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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
ΔVCH/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
ΔICH/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 Ω
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.
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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
TC
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.
AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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Typical Characteristics
Charge Current vs. RSET
RSET (kΩ
Ω
)
ICH (mA)
10
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 (°
°
C)
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 (°
°
C)
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
Ω
)
Temperature (
°
C)
ITK (mA)
80
90
100
110
120
-50 -25 0 25 50 75 100
Charge Current vs. Temperature
(ADPSET = 8.06kΩ
Ω
)
Temperature (
°
C)
ICH (mA)
900
920
940
960
980
1000
1020
1040
1060
1080
1100
-50 -25 0 25 50 75 100
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Typical Characteristics
Charge Current vs. Battery Voltage
(ADPSET = 8.06kΩ
Ω
; 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
Ω
)
Supply Voltage (V)
ICH (mA)
0
200
400
600
800
1000
1200
4.0 4.5 5.0 5.5 6.
0
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
Ω
)
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 (°
°
C)
Counter Timeout (%)
-10
-8
-6
-4
-2
0
2
4
6
8
10
-50 -25 0 25 50 75 100
AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
PRODUCT DATASHEET
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Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
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Typical Characteristics
CT Pin Capacitance vs. Counter Timeout
Time (hours)
Capacitance (μ
μ
F)
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 (°
°
C)
TS Pin Current (
μ
A)
72
74
76
78
80
82
84
86
88
-50 -25 0 25 50 75 10
0
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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 exceed-
ing 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 sys-
tem thermal regulation becomes active, the programmed
constant current charge amplitude will be automatically
reduced to a safe level for the current operating condi-
tion. Should the ambient operating temperature drop
below the thermal loop threshold, the system will auto-
matically resume charging at the full programmed con-
stant current level. This intelligent thermal management
system permits the AAT3687 to operate and safely
charge a battery cell over a wide range of ambient condi-
tions while maximizing the greatest possible charge cur-
rent 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
Current
Compare
ADP
BAT
A
DPSET
UVLO
Over-
Temperature
Protection
Charge
Status
STAT2
STAT1 TS
Window
Comparator
80μA
4.2V
Serial
Data
DATA Watchdog
Timer CT
Voltage
Sense
ADPP#
EN
GND
IC enable
1. Precharge applies to AAT3687 and AAT3687-1 only.
AAT3687
Lithium-Ion/Polymer Battery ChargerBatteryManagerTM
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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.
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System Operation Flow Chart
Yes Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
Set
Enable
Timing
Expire
Yes
(AAT3687)
TERM
Yes
BAT_EOC
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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 (kΩ)I
CC
ADP
RSET (kΩ)
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.
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RSET (kΩ
Ω
)
ICH (mA)
10
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 10kΩ 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
AAT3687
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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 10kΩ
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:
(V
ADP -
V
F(LED)
)
R
B(STAT1/2)
= I
LED(STAT1/2)
Example:
Eq. 3:
(5.5V
- 2.0
V)
R
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.
8
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.
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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 1.5kΩ 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:
V
PULL-UP
R
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
R
PULL_UP
μP GPIO
Port
GPIO
IN
IN
OUT
OUT
Figure 3: Data Pin Application Circuit.
Timing Diagram
SQ
SQ
PULSE
Data
System Reset
System Start
CK
T
SYNC
T
LAT
N=1 N=2 N=3
T
OFF
T
DATA(RPT)
= T
SYNC
+ T
LAT
< 2.5 P
DATA
T
OFF
> 2 P
DATA
P
DATA
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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
θJA = 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
θJA = 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.
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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 Evaluation Board Schematic Diagram
D2 D1
RED
LED
RED
LED
GRN
LED
D3
Open
R1
C1
10μF
C2
10μF
R2
10kΩ
R6
8.06kΩ
R7
1.5kΩ
R5
1.5kΩ
R4
1.5kΩ
R3
1.5kΩ
C3
0.1μF
SW1
DAT
A
CT
123
ON/OFF
TermB3
TermB2
TermB2
J1
1
2
1
2
3
ADP
BAT
TS
GND
GND
ADP
2
EN
4
GND
310
BAT
1
ADPP# 5
TS
6
DATA 7
STAT2 8
STAT1 9
CT
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, 10kΩ, 1/16W 5%
0603 SMD R2 0603 Panasonic/ECG P10KCFCT-ND
1Resistor, 8.06kΩ, 1/16W 1%
0603 SMD R6 0603 Panasonic/ECG P8.06KHCT-ND
4Resistor, 1.5kΩ, 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 AnalogicTech AAT3687IWP-4.2
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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
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor
products that are in compliance with current RoHS standards, including the requirement that lead not
exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at
http://www.analogictech.com/aboutus/quality.php.
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
0.05
±
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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Phone (408) 737-4600
Fax (408) 737-4611
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual
property rights are implied. AnalogicTech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
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design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specifi c testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
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