AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 1
www.analogictech.com
Typical Application
BATT-
TEMP
Battery
Pack
VPIN
VPIN
EN
TS
LX BATT+
Adapter
22µF
CS
BAT
PGND
STAT2
STAT1
CT
4.7µH
GND
Charge Enable
Timer Disable
Charging Status 1
Charging Status 2
ISET
TERM Termination Current Set
and Charge Current Indicator
Charge Current Set
RSET
RT
RTER M
0.1µF
VCC
0.1µF
22µF
to 47µF
+
–
General Description
The AAT3620 BatteryManager™ is a member of
AnalogicTech’s Total Power Management IC™ family.
With the many functions added to mobile devices such
as color display, camera with flash, organizer, video, etc,
the battery capacity must keep pace with the power
requirements. The AAT3620 is the ideal solution for high
capacity Li+ batteries and can supply up to 2.0A charge
current with minimal thermal impact to the system.
The AAT3620 is a PWM switch mode / linear charger with
high charge efficiency at the full constant current (fast
charge) rate. Based on a 1.5MHz PWM step-down “buck”
converter, the AAT3620 PWM switch mode controls the
constant current charge mode up to 2.0A, and auto-
matically switches to linear mode charging during the
battery conditioning low level current and the light load
end of charge current termination region. The full charge
rate and the end of charge current can be programmed
with separate external resistors. A shared charge current
indication pin is available for a Coulomb counter.
Battery charge temperature and charge state are fully
monitored for fault conditions. In the event of an over-
current, over-voltage, short-circuit or over-temperature
failure, the device will automatically shut down. A status
monitor output pin is provided to indicate the battery
charge status and power source status though a display
LED.
The AAT3620 is available in a thermally enhanced, space-
saving 14-pin 3x3mm TDFN package that includes all
essential components for a switch-mode battery charger.
Features
• 4.3V~6.0V Input Range
• Up to 2.0A Charge Current Capability
• 1.5MHz PWM/Linear Charger
• Over 90% Full Rate Charge Efficiency
• Integrated Switching Device
• Integrated Sense Resistor
• Built-in Reverse Blocking Feature
• Battery Preconditioning/Constant Voltage/Constant
Current Charge Mode
• Programmable End of Charge Current
• 1% Constant Voltage Mode Regulation
• Built-in Programmable Charging Timer
• Charge Current Indication Pin
• Over-Voltage, Over-Current, and Over-Temperature
Protection
• Battery Over-Temperature Protection
• Power-On Reset and Soft-Start
• TDFN33-14 Package
Applications
• Digital Camcorders
• Point of Service (POS)
• Portable DVD Players
• Portable Hand-held Solutions
• Portable Media Player
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
2 3620.2009.12.1.3
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
2 3620.2009.12.1.3
www.analogictech.com
Pin Description
Pin# Name Type Function
1 VPIN In Adapter power input.
2 PGND Ground Power ground.
3 GND Ground Analog ground connection.
4 VCC In Supply Input.
5 EN In Charge enable input, active high, with internal pull-up (to VPIN).
6 ISET In Connect RSET resistor to pin to set constant current charge current.
7 CT In/Out Timer pin: connect timing capacitor here for charge timer function; connect to ground to
disables the timer function.
8 STAT2 Out Battery charge status 2 indicator pin to drive an LED, open-drain.
9 STAT1 Out Battery charge status 1 indicator pin to drive an LED, open-drain.
10 TERM In/Out Connect RTERM resistor to pin to set termination current. Charging current can be monitor
with this pin. Leave OPEN to set to 200mA default termination current.
11 TS In/Out Battery pack temperature sensing input. To disable TS function, pull up to VCC through 10k
resistor.
12 BAT Out Battery positive terminal connecting pin.
13 CS In Return pin for inductor for internal current sensing
14 LX In/Out Switching node.
EP EP Ground
The exposed thermal pad (EP) must be connected to board ground plane and pins 2 and 3.
The ground plane should include a large exposed copper pad under the package for thermal
dissipation (see package outline).
Pin Configuration
TDFN33-14
(Top View)
VPIN
PGND
GND
1
VCC
EN
ISET
LX
EP
CS
BAT
TS
TERM
STAT1
2
3
4
5
6
CT 7
12
11
14
13
10
9
STAT2
8
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 3
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 3
www.analogictech.com
Absolute Maximum Ratings1
Symbol Description Value Units
VPVPIN, LX -0.3 to 6.5 V
VNOther pins -0.3 to VP + 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
PDMaximum Power Dissipation 2.5 W
TLEAD Maximum Soldering Temperature (at Leads) 300 °C
Thermal Information
Symbol Description Value Units
θJA Maximum Thermal Resistance (3x3mm TDFN-14)250 °C/W
PDMaximum Power Dissipation32W
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.
3. Derate 2.7mW/°C above 25°C ambient temperature.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
4 3620.2009.12.1.3
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
4 3620.2009.12.1.3
www.analogictech.com
Electrical Characteristics1
VIN = 5.5V, TA = -25°C to 85°C; unless otherwise noted, typical values are at TA = 25°C.
Symbol Description Conditions Min Typ Max Units
Operation
VIN Adapter Input Voltage 4.3 6.0 V
VVIN_UVLO Input Under-Voltage Lockout VPIN Rising 3.5 4.3 V
Hysteresis 150 mV
VVIN_SLEEP Input Sleep Voltage No Charge if VVIN < VVIN_SLEEP
VBAT
+ 0.05
VBAT
+ 0.2 V
IVIN_OP Operating Supply Current EN = High, Charge Current = 200mA 5 mA
IVIN_STBY Standby Supply Current EN = High, No Charge 2 mA
IVIN_SHDN Shutdown Supply Current EN = Low, LX Floating 10 A
IFWD_LKG
Forward Leakage Current, Measured
from LX to Ground EN = Low, LX = 5.5V 1 A
IREV_LKG
Reverse Leakage Current, Measured
from LX to VIN
EN = Low or High, VIN = 0V,
LX = 5.5V 1A
IBAT_LKG Bat Pin Leakage Current VBAT = 4.2V, VIN = 0V or open 1 A
RDS(ON)
Internal PMOS On Resistance VIN = 5.5V 170 300 m
Internal NMOS On Resistance VIN = 5.5V 120 250 m
fSW PWM Switching Frequency VBAT = 3.6V 1.2 1.5 1.8 MHz
Charge Regulation
VBAT_REG Output Charge Voltage Regulation 4.158 4.20 4.242 V
tSOFT_START Charging Soft-Start Delay Delay of Charge from EN, or VVIN_UVLO,
or VVIN_ADPP
100 us
VBAT_BC
Battery Conditioning Battery Voltage
Threshold
Preconditioning Battery Charge when
VBAT < VBAT_BC
2.4 2.6 2.8 V
ICH_BC Battery Conditioning Charge Current When VBAT < VBAT_BC
ICH_ CC
x 0.1 A
ICH_BC_TYP
Typical Battery Conditioning Charge
Current Setting Range 100 200 mA
tCH_BC Battery Conditioning Time Out Stop Charge if Preconditioning Time
is more than tCH_CV
-15% 0.25
x CCT
+15% Minute/nF
ICH_CC
Constant-Current Battery Charge
Current When VBAT_BC < VBAT < VBAT_REG -15% ICH_CC +15 %
ICH_CC_TYP
Typical Constant-Current Battery
Charge Current Setting Range 12A
tCH_CCFAST Fast Constant Current Charge Time Out Stop Charge if Fast Charge Time is
more than tCH_CCFAST
-15% 0.02
x CCT
+15% Hour/nF
tCH_CV Constant Voltage Charge Time Out Stop Charge if Charge Time is more
than tCH_CV
-15% 0.03
x CCT
+15% Hour/nF
VBAT_RCH Battery Recharge Voltage Threshold If VBAT Falls Below VBAT_RCH, Recharge
Starts
VBAT_REG
- 0.1 V
ITERM Charge Termination Threshold Current Terminate CV Charge if ICH < ITERM -10 RTERM
x 10-6 10 %
ITERM_TYP
Typical Termination Threshold Current
Setting Range 50 200 mA
1. Specification over the –25°C to +85°C operating temperature range is assured by design, characterization and correlation with statistical process controls.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 5
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 5
www.analogictech.com
Electrical Characteristics1
VIN = 5.5V, TA = -25°C to 85°C; unless otherwise noted, typical values are at TA = 25°C.
Symbol Description Conditions Min Typ Max Units
Logic and Status Input/Output
VHIGH EN Input Low Threshold 1.6 V
VLOW EN Input Low Threshold 0.4 V
IEN EN Pin Supply Current EN = VIN 0.1 1 A
EN = 0V 0.6 10 A
ISLEAK STAT1, STAT2 Pin Leakage Current When output FET is off 1 A
ISTATx STAT1 and STAT2 Pin Current Sink Capability 10 mA
tSTAT_PULSE STAT Pulse Width In fault conditions 0.5 s
fSTAT_FLASH STAT Pulse Frequency In fault conditions 1 Hz
Protection
VBAT_OVP Battery Over-Voltage Protection Threshold No charge if VBAT > VBAT_OVP
VBAT_REG
+ 0.2 V
IOCP_LMT2
VBAT_OVP IDATA
Over-Current Protection Threshold and Limit 2.46 3.0 4.0 A
VTS1 TS Hot Temperature Fault Threshold 29.1 30 30.9 % VIN
mV
Hysteresis 50
VTS2 TS Cold Temperature Fault Threshold Threshold 58.2 60 61.8 % VIN
mV
Hysteresis 50
TTH Thermal Shutdown 140 °C
TTH HYS Thermal Shutdown Hysteresis 15 °C
VCT_DIS Charge Timer Disable Threshold No timer out if CT voltage
holds to be less than VCT_DIS
0.4 V
1. Specification over the –25°C to +85°C operating temperature range is assured by design, characterization and correlation with statistical process controls.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
6 3620.2009.12.1.3
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
6 3620.2009.12.1.3
www.analogictech.com
Typical Characteristics
Charging Current vs. Battery Voltage
Battery Voltage (V)
Charging Current (mA)
2.2 2.5 2.8 3.1 3.4 3.7 4.0 4.3
0
300
600
900
1200
1500
1800
2100
2400
85°C
25°C
-25°C
Constant-Current Charge Mode
Current vs. ISET Resistor
(VIN = 5V; VBAT = 3.5V)
Set Resistor (KΩ
Ω
)
Fast Charge Current (mA)
10
100
1000
10000
10010
Termination Current vs. Temperature
(VIN = 5V; RTERM = 49.9KΩ)
Temperature (°C)
Termination Current (mA)
-40 -15 10 35 60 85
40
42
44
46
48
50
52
54
56
58
60
62
64
Recharge Voltage vs. Temperature
(
VIN = 5V
)
Temperature (°C)
End of Charge Voltage (V)
-40 -15 10 35 60 85
4.050
4.055
4.060
4.065
4.070
4.075
4.080
Preconditioning Rising Threshold Voltage
vs. Temperature
(VIN = 5.5V)
Temperature (°C)
Preconditioning Rising
Threshold Voltage (V)
-40 -15 10 35 60 85
2.56
2.57
2.58
2.59
2.60
2.61
2.62
2.63
2.64
Shutdown Current vs. Input Voltage
4.5 5.0 5.5 6.0
Input Voltage (V)
Shutdown Current (μA)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-25°C
25°C
85°C
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 7
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 7
www.analogictech.com
Typical Characteristics
Charge Current vs. Input Voltage
(T = -25°C)
Input Voltage (V)
Battery Charging Current (mA)
4.0 4.4 4.8 5.2 5.6 6.04.2 4.6 5.0 5.4 5.8
0
300
600
900
1200
1500
1800
2100
2400
VBAT = 2.7V
VBAT = 3.3V
VBAT = 3.6V
VBAT = 3.9V
Charge Current vs. Input Voltage
(T = 85°C)
Input Voltage (V)
Charge Current (mA)
4.0 4.5 5.0 5.5 6.0 6.5
0
500
1000
1500
2000
2500
VBAT = 2.7V
VBAT = 3.3V
VBAT = 3.6V
VBAT = 3.9V
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
8 3620.2009.12.1.3
www.analogictech.com
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
8 3620.2009.12.1.3
www.analogictech.com
Functional Description
Control Loop
The AAT3620 uses an average current mode step-down
converter to implement the DC/DC switch-mode con-
verter function during constant current mode charging.
The technique of average current mode control over-
comes peak current control problems by introducing a
high gain integrating current error amplifier into the cur-
rent loop. Average current tracks the sensed output cur-
rent with a high degree of accuracy and the noise immu-
nity is excellent. The oscillator saw-tooth ramp provides
compensation so no slope compensation is required for
duty cycle exceeding 50%. The high gain of the current
error amplifier at DC accurately programs the output.
The switching charger works in continuous current mode
PWM only. There is a soft start before entering constant
current charging mode and the charger re-enters linear
operation in constant voltage mode when the charge
current drops below 300mA.
Linear vs. Switching Battery Charging
The AAT3620 performs battery charging using the ben-
efits of the step-down or "buck" architecture to multiply
the input current when stepping down the output volt-
age. This property is expressed mathematically in the
comparison below, and provides the ability to maximize
battery charging from current limited devices, as well as
greatly decrease power and heat related dissipation.
Linear Charging
Linear charge current relationship*:
I
BATL
= I
IN
Efficiency of linear charger:
n
L
=
V
BAT
V
IN
Functional Block Diagram
PWM / Linear Charge Control
Reverse Blocking
VPIN
VCC
EN
BAT
ISET
Over-Temperature
Protection
LX
CS
Charge
status
TS
Current
Set
GND
STAT2
Timer
CT
PGND
Reverse Blocking
CHR
TERM
VREF
STAT1
Volt Det/
UVLO
* Equation does not take into account thermal foldback.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 9
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Switch-Mode Charging
Switch-mode current relationship:
I
BATS
= n
S
· V
IN
· I
IN
V
BAT
Where nS =90%.
Example: Power Savings
Conventional Linear Charger IC:
PD = (VIN - VBAT)*IBAT = (5-3.5)*0.5 = 0.75W
Switch-Mode Charger IC:
PD = VBAT*IBAT/η - VBAT*IBAT = 3.5*0.5/0.9-3.5*0.5 = 0.195W
Adapter Input Charge
Inhibit and Resume
The AAT3620 has a UVLO and power on reset feature so
that if the input supply to the ADP pin drops below the
UVLO threshold, the charger will suspend charging and
shut down. When power is re-applied to the IN pin or the
UVLO condition recovers, the system charge control will
assess the state of charge on the battery cell and will
automatically resume charging in the appropriate mode
for the condition of the battery.
Input/Output Capacitor and Inductor
The AAT3620 contains a high performance 2A, 1.5MHz
synchronous step-down converter. The step-down con-
verter operates to ensure high efficiency performance
over all load conditions. It requires only 3 external
power components (CIN, COUT
, and L).
Apart from the input capacitor, only a small L-C filter is
required at the output side for the step-down converter
to operate properly. Typically, a 4.7H inductor such as
the Wurth 7447789004 and a 22F to 47F ceramic out-
put capacitor is recommended for low output voltage
ripple and small component size. Ceramic capacitors
with X5R or X7R dielectrics are highly recommended
because of their low ESR and small temperature coeffi-
cients. A 22F ceramic input capacitor is sufficient for
most applications.
Battery Charging
Battery charging starts only after the AAT3620 checks
several conditions in order to maintain a safe charging
environment. The input supply must be above the mini-
mum operating voltage (UVLO) and above the battery
voltage by 0.3V, the battery temperature must be within
the 0°C ~ 45°C range, and the enable pin must be high.
The AAT3620 checks the condition of the battery and
determines which charging mode to apply. If the battery
voltage is below VBAT_BC, the AAT3620 begins battery
conditioning until the battery voltage reaches VBAT_BC.
The battery conditioning current is 10% of constant cur-
rent level. At this point the AAT3620 begins constant
current mode charging. The constant current mode cur-
rent level is programmed using a single resistor from the
ISET pin to ground. Programmed current can be set from
a minimum of 1A to a maximum of 2.0A. Constant cur-
rent charging will continue until the battery voltage
reaches the voltage regulation point VBAT_REG. When the
battery voltage reaches VBAT_REG, the AAT3620 will transi-
tion to constant-voltage mode. The regulation voltage is
factory programmed to a nominal 4.2V and will continue
charging until the charging current has reduced to the
termination current programmed by the resistor con-
nected from ITERM to ground. The termination current
program range is from 50mA to 200mA. After the charge
cycle is complete, the AAT3620, turns off the series pass
device and automatically goes into a power saving sleep
mode. During this time the series pass device will block
current in both directions therefore preventing the bat-
tery from discharging through the IC.
The AAT3620 will remain in sleep mode, even if the
charger source is disconnected, until either the battery
terminal voltage drops below the VBAT_RCH threshold, the
charger EN pin is recycled, or the charging source is
reconnected. In all cases the AAT3620 will monitor all
parameters and resume charging in the most appropri-
ate mode.
Figure 1 illustrates the entire battery charging profile,
which consists of three phases.
1. Preconditioning-Current Mode (Trickle) Charge
2. Constant-Current Mode Charge
3. Constant-Voltage Mode Charge
The battery preconditioning current is equal to 10% of
the constant current charging level, so the battery pre-
conditioning current set range is 100mA to 200mA.
Linear mode is on standby while switch-mode is active in
the constant current charging region 2.6V < VBAT < 4.2V.
The charger will re-enter linear mode while in constant
voltage mode after the switch-mode current drops below
300mA. The termination current is programmed by an
external resistor with a separate ITERM pin and the ter-
mination current set pin also monitors the charge cur-
rent. The output short circuit current is equal to the bat-
tery preconditioning current.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
10 3620.2009.12.1.3
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Preconditioning Trickle Charge
Battery charging commences only after the AAT3620
battery charger checks several conditions in order to
maintain a safe charging environment. The System
operation flow chart for the battery charger operation is
shown in Figure 4. The input supply must be above the
minimum operating voltage (UVLO) and the enable pin
(EN) must be high (it is internally pulled up). When the
battery is connected to the BAT pin, the battery charger
checks the condition of the battery and determines
which charging mode to apply.
Preconditioning-Current
Mode Charge Current
If the battery voltage is below the Preconditioning
Voltage Threshold VCH_BC, the battery charger initiates
precondition trickle charge mode and charges the bat-
tery at 10% of the programmed constant-current mag-
nitude. For example, if the programmed current is 1A,
the trickle charge current will be 100mA. Trickle charge
is a safety precaution for a deeply discharged cell. It also
reduces the power dissipation in the internal series pass
MOSFET when the input-output voltage differential is at
its highest.
Constant-Current Mode Charge Current
Trickle charge continues until the battery voltage reach-
es VBAT_BC. At this point the battery charger begins con-
stant-current charging. The current level default for this
mode is programmed using a resistor from the ISET pin
to ground. Programmed current can be set at a mini-
mum of 100mA and up to a maximum of 2.0A.
The AAT3620 contains a high performance 2A, 1.5MHz
synchronous step-down converter. The step-down con-
verter operates to ensure high efficiency performance
over all load conditions. It requires only 3 external
power components (CIN, COUT
, and L).
Constant-Voltage Mode Charge
Constant current charging will continue until the battery
voltage reaches the Output charge voltage regulation
point VBAT_REG. When the battery voltage reaches VBAT_REG,
the battery charger transitions to constant-voltage
mode. VBAT_REG is factory programmed to 4.2V (nominal).
Charging in constant-voltage mode will continue until
the charge current has reduced to the programmed end
of charge termination current.
Constant Current
Fast Charge Phase
Preconditioning
Trickle
Charge
Phase
Charge Complete
Regulated Voltage
4.2
Constant Current
Mode Voltage
Threshold
2. 6
Regulated
Current
1C
Trickle Charge and
Termination Threshold
(Programmable)
Battery Recharge
Voltage Threshold
Battery Discharge
Constant Voltage
Taper Charge Phase
Constant Voltage
Taper Charge Phase
VI
0.1C
Regulated
Current
300mA
L
S
L
S
L
Charge Phase
Constant Current
12323
Figure 1: Current vs. Voltage and Charger Time
Li-ion Battery Charging and Recharge Profile.
The profile consists of three phases:
1. Preconditioning-Current Mode (Trickle) Charge - Linear Mode
2. Constant-Current (Fast) Mode Charge - Switching Mode
3. Constant-Voltage Mode (Taper) Charge - Switching/Linear Mode.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 11
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AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
3620.2009.12.1.3 11
www.analogictech.com
System Operation Flowchart
Power On Reset
Power
Input Voltage
VIN: , VPIN VCC
VIN > VUVLO
Fault
Conditions Monitoring
OV, OT,
V
TS1
< TS < V
TS2
Preconditioning
Test
VBAT < VBAT_BC
VBAT > VBAT_BC
Current Phase Test
VBAT < VBAT_EOC
VBAT > VBAT_EOC
Voltage Phase Test
IBAT > ITE RM
IBAT < ITERM
No
No
Yes
No
Preconditioning
(Trickle Charge)
Constant
Current Charge
Mode
Constant
Voltage Charge
Mode
Yes
Yes
Yes
Charge Completed
Charge Timer
Control
No
Recharge Test
VBAT
> VBAT_RCH
Yes
No
Shut Down Yes
Enable
Yes
No
No
Expired
Figure 2: System Operation Flowchart for the Battery Charger.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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Power Saving Mode
After the charge cycle is complete, the battery charger
turns off the series pass device and automatically goes
into a power saving sleep mode. During this time, the
series pass device will block current in both directions to
prevent the battery from discharging through the battery
charger.
The battery charger will remain in sleep mode even if the
charger source is disconnected. It will come out of sleep
mode if either the battery terminal voltage drops below
the VBAT_RCH threshold, the charger EN pin is recycled, or
the charging source is reconnected. In all cases, the bat-
tery charger will monitor all parameters and resume
charging in the most appropriate mode.
Programming Charge Current (ISET)
The default constant current mode charge level is user
programmed with a set resistor placed between the ISET
pin and ground. The accuracy of the constant charge cur-
rent, as well as the preconditioning trickle charge cur-
rent, is dominated by the tolerance of the set resistor. For
this reason, a 1% tolerance metal film resistor is recom-
mended for the set resistor function. The constant charge
current levels from 1A to 2A may be set by selecting the
appropriate resistor value from Table 1 and Figure 3.
Constant Charging
Current ICH_CC (mA) Set Resistor Value (kΩ)
1000 50
1100 55
1200 60
1300 65
1400 70
1500 75
1600 80
1700 85
1800 90
1900 95
2000 100
Table 1: Constant Current Charge vs. ISET
Resistor Value.
Constant-Current Charge Mode
Current vs. ISET Resistor
(VIN = 5V; VBAT = 3.5V)
ISET Resistor (KΩ
Ω
)
Fast Charge Current (mA)
403020 6050 8070 10090
400
600
800
1000
1200
1400
1600
1800
2000
Figure 3: Constant-Current Mode Charge ICH_CC
Setting vs. ISET Resistor.
Programmable Charge
Termination Current
The charge termination current ITERM can be programmed
by connecting a resistor from TERM to GND:
ITERM = · 10-6
RTERM
If the TERM pin is left open, the termination current will
set to 200mA as the default value.
When the charge current drops to the defaulted 10% of
the programmed charge current level or programmed
terminated current in the constant voltage mode, the
device terminates charging and goes into a sleep state.
The charger will remain in this sleep state until the bat-
tery voltage decreases to a level below the battery
recharge voltage threshold (VBAT_RCH).
Consuming very low current in sleep state, the AAT3620
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
AAT3620 input voltage drops, the device will enter sleep
state and automatically resume charging once the input
supply has recovered from the fault condition.
The TERM pin can also be used as a charge current
monitor based on the following equation:
Charge Current Voltage Level = 1A/V
AAT3620
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PRODUCT DATASHEET
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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-
ode and the STAT pins. LED current consumption will add
to the overall thermal power budget for the device pack-
age, 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 follow-
ing formula:
(V
IN -
V
F(LED)
)
R
BALLAST
= I
LED
Example:
(5.0V
- 2.0
V)
R
BALLAST
= = 1.5kΩ
2mA
Note: Red LED forward voltage (VF) is typically 2.0V @
2mA.
Protection Circuitry
Charge Safety Timer (CT)
While monitoring the charge cycle, the AAT3620 utilizes
a charge safety timer to help identify damaged cells and
to ensure that the cell is charged safely. Operation is as
follows: upon initiating a charging cycle, the AAT3620
charges the cell at 10% of the programmed maximum
charge until VBAT > 2.6V. If the cell voltage fails to the
precondition threshold of 2.6V (typ) before the safety
timer expires, the cell is assumed to be damaged and
the charge cycle terminates. If the cell voltage exceeds
2.6V prior to the expiration of the timer, the charge cycle
proceeds into fast charge. Three timeout periods of 25
minutes for Trickle Charge mode, 2 hours for Constant
Current Mode and 3 hours for Constant Voltage mode.
Status Indicator (STAT1/2)
Charge Status Output
The AAT3620 provides battery charge status via two status pins (STAT1 and STAT2). Each of the two pins is internally
connected to an N-channel open drain MOSFET. The status pins can indicate the following conditions:
Option 1: Default Option STAT1 STAT1 (50% Duty Cycle) STAT2 STAT2 (50% Duty Cycle)
Pre-Charge ON ON
Fast-Charge ON OFF
End of Charge (Charge Complete) OFF ON
Charge Disabled OFF OFF
Sleep Mode OFF OFF
No Battery (with Charge Enabled) ON ON
Fault Condition (Battery 0V) OFF OFF
Fault Condition (Battery OT/UT) OFF OFF
Fault Condition (Device OT) OFF OFF
Fault (Time Out) OFF OFF
TERM (Current reached in CVM) OFF OFF
Option 2 STAT1 STAT1 (50%) STAT2 STAT2 (50%)
Pre-Charge ON OFF
Fast-Charge ON OFF
End of Charge (Charge Complete) OFF OFF
Charge Disabled OFF OFF
Sleep Mode OFF OFF
No Battery (with Charge Enabled) ON OFF
Fault Condition (Battery 0V) OFF ON
Fault Condition (Battery OT/UT) ON ON
Fault Condition (Device OT) ON ON
Fault (Time Out) OFF ON
TERM (Current reached in CVM) OFF OFF
Table 2: Constant Current Charge vs. ISET Resistor Value.
AAT3620
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Mode Time
Trickle Charge (TC) Time Out 25 minutes
Trickle Charge (TC) + Constant Current
(CC) Mode Time Out 2 hours
Constant Voltage (VC) Mode Time Out 3 hours
Table 3: Summary for a 0.1μF Ceramic Capacitor
Used for the Timing Capacitor.
The AAT3620 has a battery fault detector, which, when
used in conjunction with a 0.1F capacitor on the CT pin,
outputs a 1Hz signal with 50% duty cycle at the STAT1
pin in the event of a timeout while in the trickle charge
mode.
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 0.1F value, the time-out peri-
ods would be doubled. If the programmable watchdog
timer function is not needed, it can be disabled by termi-
nating the CT pin to ground. The CT pin should not be left
floating or unterminated, as this will cause errors in the
internal timing control circuit. The constant current pro-
vided to charge the timing capacitor is very small, and
this pin is susceptible to noise and changes in capaci-
tance 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 dominated by the capacitance value, a
10% tolerance or better ceramic capacitor is recom-
mended. Ceramic capacitor 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 battery
charge voltage and is set by the over-voltage protection
threshold (VBAT_OVP). If an over-voltage condition occurs,
the AAT3620 charge control will shut down the device
until the voltage on the BAT pin drops below VBAT_OVP
. The
AAT3620 will resume normal charging operation after the
over-voltage condition is removed. During an over-volt-
age event, the STAT LEDs will report a system fault.
Over-Temperature Shutdown
The AAT3620 has a thermal protection control circuit
which will shut down charging functions should the inter-
nal die temperature exceed the preset thermal limit
threshold. Once the internal die temperature falls below
the thermal limit, normal operation will resume the pre-
vious charging state.
Battery Temperature Fault Monitoring (TS)
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 STAT pins.
After the system recovers from a temperature fault, the
device will resume charging operation. The AAT3620
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.
The internal battery temperature sensing system (Figure
3) is comprised of two comparators which establish a
voltage window for safe operation. The thresholds for the
TS operating window are bounded by the VTS1 and VTS2
specifications. Referring to the electrical characteristics
table in this datasheet, the VTS1 threshold = 0.30 · VIN
and the VTS2 threshold = 0.60 · VIN. An external resistor
RT with a value equal to the NTC thermistor resistance
must be connected between TS and VIN.
This system is intended for use with negative tempera-
ture coefficient thermistors (NTC) which are typically
integrated into the battery package. Most of the com-
monly used NTC thermistors in battery packs are
approximately 10k at room temperature (25°C). If the
battery becomes too hot during charging due to an
internal fault or excessive constant charge current, the
thermistor will heat up and reduce in value, pulling the
TS pin voltage lower than the TS1 threshold, and the
AAT3620 will stop charging until the condition is
removed, when charging will be resumed. If the use of
the TS pin function is not required by the system, it
should be tied to VPIN using a 10k resistor.
0.60x V
IN
x V
IN
V
IN
Battery Cold Fault
Battery Hot Fault
VPIN
TS
Battery
Pack
Figure 3: AAT3620 Battery Temperature
Sense Circuit.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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Thermal Considerations
The actual maximum charging current is a function of
Charge Adapter input voltage, the state of charge of the
battery at the moment of charge, the system supply cur-
rent from the BAT pin, the ambient temperature and the
thermal impedance of the package. The maximum pro-
grammable current may not be achievable under all
operating parameters.
The AAT3620 is offered in a TDFN33-14 package which
can provide up to 2W of power dissipation when it is
properly bonded to a printed circuit board and has a
maximum thermal resistance of 50°C/W. Many consider-
ations 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 gen-
erating devices in a given application design. The ambi-
ent temperature around the charger IC will also have an
effect on the thermal limits of a battery charging applica-
tion. The maximum limits that can be expected for a
given ambient condition can be estimated by the follow-
ing discussion. First, the maximum power dissipation for
a given situation should be calculated:
(T
J(MAX) -
T
A
)
P
D(MAX)
= θ
JA
Where:
PD(MAX) = Maximum Power Dissipation (W)
JA = Package Thermal Resistance (°C/W)
TJ(MAX) = Maximum Device Thermal Shutdown Temperature
(°C) [140°C]
TA = Ambient Temperature (°C)
The power dissipation for both the linear charging mode
and the switching charger mode should be considered.
The power dissipation for the switching charger can be
calculated by the following equation:
PD(MAX) =
+ [(tSW · fSW · ICH_CC + IqOP) · VPIN]
ICH_CC2 · [RDSONHS · VBAT + RDSONLS · (VPIN - VBAT)]
VPIN
Where:
PD(MAX) = Total Power Dissipation by the Device
VPIN = Adapter Input Voltage
VBAT = Battery Voltage at the BAT Pin
ICH_CC = Constant Charge Current Programmed for the
Application
IQOP = Quiescent Current Consumed by the IC for Normal
Operation [5mA]
RDS(ON)HS and RDS(ON)LS = On-resistance of step-down high
and low side MOSFETs
The power dissipation for the linear charging mode can
be calculated by the following equation:
PD(MAX) = [(VPIN - VBAT) · ICH_BC + (VPIN • IQOP)]
Where:
PD(MAX) = Total Power Dissipation by the Device
VPIN = Input Voltage
VBAT = Battery Voltage as Seen at the BAT Pin
ICH_BC = Battery Conditioning Charge Current Programmed
for the Application
IQOP = Quiescent Current Consumed by the Charger IC
for Normal Operation [5mA]
By substitution, we can derive the maximum charge cur-
rent before reaching the thermal limit condition (thermal
loop). The maximum charge current is the key factor
when designing battery charger applications.
(P
D(MAX) -
T
A ·
I
QOP
)
V
PIN -
V
BAT
I
CH_BC(MAX)
=
(T
J -
T
A)
θJA -
V
IN -
I
OP
V
IN -
V
BAT
I
CH(MAX)
=
In general, the worst condition is the greatest voltage
drop across the charger IC, when battery voltage is
charged up to the preconditioning voltage threshold and
entering Constant Current switching charge mode.
Example Worst Case Power Dissipation
The worst case power dissipation can be calculated using
the lowest battery voltage level when the charger enters
CC charge mode and the charge current is set to 2A.
ICH_CC = 2A
VPIN =6V
RDSONHS = 0.3
RDSONLS = 0.25
tSW = 5 · 10-9
IQOP = 0.005A
fSW = 1.5 · 106
TA = 85°C
JA = 50°C/W
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
16 3620.2009.12.1.3
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AAT3620
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PRODUCT DATASHEET
16 3620.2009.12.1.3
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PD(MAX) = (2A)2 · [0.3Ω · 2.8V + 0.25Ω · (6V - 2.8V)]
6V
+ [(5 · 10-9 · [1.5 · 106]· 2A + 0.005A) · 6V]
PD(MAX) = 1.213W
TJ(MAX) = 85 + 50 · 1.213
TJ(MAX) = 145.65
For the Linear Mode:
IQOP = 0.005A
VPIN = 6V
VBAT = 2V
ICH_BC = 0.2A
PD(MAX) = [(6V - 2V) · 0.2A + (6V · 0.005A)]
PD(MAX) = 0.83W
Layout Guidance
Figure 5 is the evaluation board schematic. The evalua-
tion board has additional components for easy evalua-
tion; the actual bill of materials required for the system
is shown in Table 4. When laying out the PC board, the
following layout guidelines should be followed to ensure
proper operation of the AAT3620:
1. The exposed pad EP must be reliably soldered to
PGND/AGND and multilayer GND. The exposed ther-
mal pad should be connected to board ground plane
and pins 2 and 3. The ground plane should include a
large exposed copper pad under the package with
vias to all board layers for thermal dissipation.
2. The power traces, including GND traces, the LX
traces and the VIN trace should be kept short, direct
and wide to allow large current flow. The L1 connec-
tion to the LX pins should be as short as possible.
Use several via pads when routing between layers.
3. The input capacitors (C1, C5, C6, and C7) should be
connected as close as possible to VPIN (Pin 1) VCC
(Pin 4) and GND/PGND (Pin 2,3) to get good power
filtering.
4. The output capacitors C2, C4, and C9 and inductor L1
should be connected as close as possible and there
should not be any signal lines under the inductor.
5. The resistance of the trace from the load return to the
PGND (Pin 2) should be kept to a minimum. This will
help to minimize any error in DC regulation due to
differences in the potential of the internal signal
ground and the power ground.
BAT
GND
TS
TB1
VPIN
1
PGND
2
GND
3
VCC
4
EN
5
ISET
6
CT
7STAT2 8
BAT 12
STAT1 9
TERM 10
TS 11
CS 13
LX 14
EP
AAT3620-TDFN33-14
U1
4.7μH
L1
47μF
C4
JP3 (open)
EN
JP1
STAT1
D1
STAT2
D2
100k
R4 49.9k
R3
10k
R1
10k
R2
VIN
TS
JP2
0.1μF
C3
2k
R5
2k
R6
VIN
0.1μF
C1
22μF
C6
VIN
TB2
GND
10μF
C5
TS
TP7
GND
TP6
VIN
TP1
CS
TP5
LX
TP4
BAT
TP8
VCC
TP2
22μF
C2
100
R7
GND
TP3
100μF
(Optional)
C7
Figure 5: AAT3620 2A Evaluation Kit Schematic.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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Quantity Value Designator Footprint Description
110F C5 0603 Capacitor, Ceramic, X5R, 10V, ±20%
2 0.1F C1, C3 0402 Capacitor, Ceramic, 20%, 10V, X5R
222F C2, C6 1206 Capacitor, Ceramic, 20%, 10V, X5R
1 (Optional) 100F C10 C Capacitor, Tantalum, 16V, 10%
147F C4 1206 Capacitor, Ceramic, 20%, 10V, X5R
1 4.7H L1 7mm x 7mm Inductor, Wurth, 7447789004
2 10K R1, R2 0402 Resistor, 5%
2 2k R5, R6 0402 Resistor, 5%
1 49.9k R3 0402 Resistor, 1%
1 100k R4 0402 Resistor, 1%
1 100 R7 0402 Resistor, 1%
2 LED D1, D2 0402 Red and Green SMD
Table 4: Minimum AAT3620 Bill of Materials.
Figure 6: AAT3620 Evaluation Kit Top Layer. Figure 7: AAT3620 Evaluation Kit Bottom Layer.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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AAT3620
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Ordering Information
Package Part Marking1Part Number (Tape and Reel)2
TDFN33-14 6WXYY AAT3620IWO-4.2-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.
Packaging Information
TDFN33-14
Top View Bottom View
3.000
±
0.050
Index Area
3.000
±
0.050
Detail "A"
1.650
±
0.050
2.500
±
0.050
0.203 REF
0.750
±
0.050
0.000
+
0.100
- 0.000
Detail "A"
Side View
0.425
±
0.050
0.400 BSC
0.180
±
0.050
Pin 1 Indicator
(Optional)
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.
AAT3620
1-Cell Li+ Switch Mode Battery Charger BatteryManagerTM
PRODUCT DATASHEET
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AAT3620
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Phone (408) 737-4600
Fax (408) 737-4611
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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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