DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
General Description
Features
The AAT3670 BatteryManager is a highly integrated single-cell lithium-ion/polymer (Li-ion) battery charger and
system power management IC that enables simultaneous battery charging and full system usage without compromising the battery’s charge cycle life. It operates with
low-voltage AC adapter (ADP) and USB inputs and
requires a minimum number of external components.
• ADP, USB, or Battery Powers System Load Through
Internal Current-Limited Switches
• Simultaneous Battery Charging and System Usage
• Voltage Sensed Charge Reduction Loop to Minimize
Charge Time, Even While the System Operates
• Digitized Thermal Loop
• Battery Power Enable (ENBAT)
• Battery Charge Timer (CT)
• Battery Temperature Monitoring (TS)
• Battery Charge Status Report (STATx)
• Automatic Recharge Sequencing
• Battery Under-Voltage, Over-Voltage, and OverCurrent Protection
• System Load Current Limiting
• Thermal Protection
• 24-pin 4 × 4mm QFN Package
The AAT3670 selects ADP or USB to power the system
load and charge the battery when ADP/USB power is
available. The AAT3670 precisely regulates battery
charge voltage and current for 4.2V Li-ion cells. Charge
current can be programmed up to 1.6A for ADP charging
and 0.9A or 0.1A for USB charging by resistors on the
ADPSET / USBSET pins. The charge termination current
threshold is set by an external resistor on the TERM pin.
The AAT3670 has a voltage-sensed charge current
reduction loop that enables system operation without a
power shortage. When the input voltage falls below the
programmable charge reduction threshold, the device
automatically reduces the charge current until the input
voltage returns to the threshold voltage.
Applications
•
•
•
•
•
•
Battery temperature and charge state are fully monitored
for fault conditions. In the event of a battery over-voltage/short-circuit/over-temperature condition, the charger will automatically shut down, protecting the charging
device, control system, and battery. Two status monitor
output pins (STAT1 and STAT2) are provided to indicate
battery charge status by directly driving external LEDs.
Cellular Telephones
Digital Still Cameras
Personal Data Assistants (PDAs)
Hand Held PCs
MP3 Players and PMP
Other Li-ion Battery Powered Devices
The AAT3670 is available in a Pb-free, thermallyenhanced, space-saving 24-pin 4 × 4mm QFN package.
Typical Application
STAT1
OUT
STAT2
BATS
BAT
ADP
Adapter Input
CADP
10μF
Single Cell
Li-Ion/Poly
Battery
RT
TS
EN
Enable
T
VTS
CUSB
10μF
ENBAT
Enable Battery to OUT
CHRADP
USBSEL
USB Hi/Lo Select
CHRUSB
ADPSET
USBSET
ADPLIM
USBLIM
RUSBSET
CBAT
10μF
AAT3670
USB
USB Input
RADPSET
System Load
RADPLIM
RUSBLIM
CT
TERM
CT
GND
RTERM
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1
DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Pin Descriptions
Pin #
2
Name
Type
1
USBSEL
I
2, 3
OUT
O
4, 5
BAT
I/O
6
7
ADP
VTS
I
O
8
TS
I
9
BATS
I
10
CHRADP
I/O
11
ADPLIM
I
12
USBLIM
I
13
ADPSET
I
14
USBSET
I
15
GND
I/O
16
TERM
I
17
EN
I
18
CT
I
19
20
21
STAT2
STAT1
N/C
O
O
22
USB
I
23
CHRUSB
I/O
24
EP
ENBAT
I
Function
Logic input. High for 100% USB charge current set by USBSET; low for 20% (constant current charge mode) or 50% (trickle charge mode) charge current set by the USBSET resistor.
System load output; a capacitor with a minimum value of 10μF (including all capacitance on
the load of OUT) is required.
Battery pack input/output. For best operation, a 1μF ceramic capacitor should be placed
between BAT and GND.
AC adapter input, source of system load and battery charging. Minimum 1μF input capacitor.
Voltage reference for battery temperature sensing.
Battery temperature sensing input. Use an NTC resistor from TS pin to ground and a 1%
standard resistor that has equal resistance of the NTC at 25°C from VTS to TS for battery
temperature sensing. Tie TS pin to ground to disable the temperature sensing function.
Battery sense pin.
ADP voltage sensed charge reduction programmable pin. A resistor divider from ADP to this
pin and GND sets the charge reduction threshold. When this pin is open, the charge reduction threshold is 4.6V. If this pin is tied to the ADP pin, the charge reduction is disabled.
Connect a resistor to this pin to set the ADP input current limit (including load switch and
charger currents).
Connect a resistor to this pin to set the USB input current limit (including load switch and
charger currents).
Connect a resistor to this pin to set the ADP charge current (for trickle charge and constant
current charge). The CC current set by this pin should be less than the current limit set by
ADPLIM, otherwise the CC current will be limited by ADPLIM.
Connect a resistor to this pin to set the USB charge current (for trickle charge and constant
current charge). The CC current set by this pin should be less than the current limit set by
USBLIM, otherwise the CC current will be limited by USBLIM.
Common ground.
Connect a resistor to this pin to program the charge termination current threshold. No termination current setting when this pin is pulled up to a logic high level.
ADP/USB enable input. High or floating (internal pull-up) to enable ADP/USB switch and ADP/
USB battery charging; low to disable ADP/USB switch and ADP/USB battery charging.
Battery charge timer input pin. Connect a capacitor to this pin to set the ADP charge timers.
No time-out for USB charging. Timers are disabled when this pin is grounded. The timer is
suspended if the battery temperature is not within 0 to 50ºC or is in charge reduction (either
due to the supply voltage dropping or the device temperature rising) is activated. The timer
continues where it left off after the battery temperature returns to normal and the device is
out of the charge reduction loops.
Open drain charger status reporting.
Open drain charger status reporting.
No connection.
USB input, source of system load and battery charging when ADP is not available. Minimum
1μF input capacitor.
USB voltage sensed charge reduction programmable pin. A resistor divider from USB to this
pin and GND sets the charge reduction threshold. When this pin is open, the charge reduction threshold is 4.5V. If this pin is tied to the USB pin, charge reduction is disabled.
Battery load switch enable, active high.
Exposed paddle (bottom). Connect to ground as closely as possible to the device.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Pin Configuration
QFN44-24
(Top View)
STAT2
STAT1
N/C
USB
CHRUSB
ENBAT
19
20
21
22
23
24
USBSEL
OUT
OUT
BAT
BAT
ADP
1
18
2
17
3
16
4
15
5
14
6
13
CT
EN
TERM
GND
USBSET
ADPSET
12
11
9
10
8
7
USBLIM
ADPLIM
CHRADP
BATS
TS
VTS
Absolute Maximum Ratings1
Symbol
VP
VP
VN
TJ
TLEAD
Description
ADP, USB, BAT, OUT, BATS VUVLO
Yes
Switch
On
No
No
Thermal
Loop Enable
Sleep
Mode
No
Fault
Condition
Monitor
OV, OT,
OC
Enable
Dynamic Charge
VEN_BAT > VEN
Yes
Yes
No
Shutdown
Mode
Device
Temp. Monitor
TJ > 110degC
Yes
No
Connect
ADP to BAT
and OUT
Yes
Battery Temp.
Sense
VTS1 < TS < VTS2
No
Thermal Loop
Current Reduction
Battery
Temperature
Fault
Expire
Charge Timer
(Enable on
Charger reset)
Power
Share
Recharge Test
VRCH > VBAT ?
Yes
Preconditioning
Test
VMIN > VBAT
Yes
Low Current
Conditioning
Charge
Set
No
No
Current Limit
Test
IOUT > ILIM
Yes
Reduce Charging
Current to BAT
Current Phase
Test
VEOC > VBAT
Yes
Constant Current
Charging Mode
No
Voltage Phase
Test
IBAT > ITERM
Yes
Constant Voltage
Charge Mode
Charge Reduction
Mode
No
IOUT + IBAT > ILIM ?
No
Yes
Yes
Charge
Complete
Voltage
Regulation
Enable
Input Voltage
Level Test
VADP < VCHR_TH
No
Figure 2: AAT3670 Operational Flow Chart.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Applications Information
The following equation may be used to approximate the
ADP charge reduction threshold above or below 4.5V:
AC Adapter/USB System Power Charging
Adapter Input Mode
In the adapter mode, constant current charge levels up
to 1.6A may be programmed by the user. The AAT3670
system control will always select the adapter input over
the USB supply input when ever voltage is present on
the ADP pin. The ADP input will operate over a range
from 4.35V to 5.5V.
The constant fast charge current for the adapter input
mode is set by the RADPSET resistor connected between the
ADPSET pin and ground. The battery preconditioning or
trickle charge current is fixed at 10% of the programmed
fast charge constant current level. Refer to Table 2 for
recommended RADPSET values for a desired constant current charge level. Battery charging states will be indicated via the STAT1 and STAT2 display LEDs. Please
refer to the Battery Charge Status Indication discussion
for further details on data reporting.
Eq. 1: VADPCHR =
2.0V
(R12/[R12 + R11])
where R11 and R12 < 500k.
VADP
R11
ADP
850k
CHRADP
VCHR = 2.0V
R12
650k
ADP Charge Reduction
Under normal operation, the AAT3670 should be operated
from an adapter power source with a sufficient capacity
to supply the desired constant charge current plus any
additional load which may be placed on the source by the
operating system. In the event that the power source to
the ADP pin is unable to provide the programmed fast
charge constant current, or if the system under charge
must also share supply current with other functions, the
AAT3670 will automatically reduce the ADP fast charge
current level to maintain the integrity of the source supply, power the operating system, and charge the battery
cell with the remaining available current.
The ADP charge reduction system becomes active when
the voltage on the ADP input falls below the ADP charge
reduction threshold (VCHRADP), which is preset to 4.6V.
Should the input supply drop below the VCHRADP threshold,
the charge reduction system will reduce the fast charge
current level in a linear fashion until the voltage sensed
on the ADP input recovers to a point above the charge
reduction threshold voltage. The ADP charge reduction
threshold (VCHRADP) may be externally set to a value other
than 4.6V by placing a resistor divider network between
the ADP pin and ground with the center connected to the
CHRADP pin. The ADP charge reduction feature may be
disabled by shorting the CHRADP pin directly to the ADP
input pin.
20
Figure 3: Internal Equivalent Circuit for the
CHRADP Pin.
Adapter Input Charge Inhibit and Resume
The AAT3670 has an under-voltage lockout (UVLO) and
power on reset feature to protect the charger IC in the
event the input supply to the adapter pin drops below
the UVLO threshold. Under a UVLO condition, the charger will suspend the charging process. When power is
re-applied to the adapter pin or the UVLO condition
recovers, the system charge control will asses the state
of charge on the battery cell and will automatically
resume charging in the appropriate mode for the condition of the battery.
USB Input Mode
The AAT3670 provides an input for intelligent USB charging. When no voltage is present on the adapter input pin,
the charge controller will automatically switch to accepting power from the USB input. The USB charge mode
provides two programmable fast charge levels, USB high
(USBH) and USB low (USBL). The USBH mode can be set
as high as 900mA; however for most applications utilizing a USB port as the source supply, 500mA is the typical
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
default USBH value and USBL is subsequently set for
100mA. In the USBL fast charge mode, the constant
charging current is set to 20 percent of the programmed
USBH. More simply put, the USBL low fast charge level
= USBH divided by five. The USBH or USBL modes may
be externally selected by USB select pin (USBSEL).
The following equation may be used to approximate a
USB charge reduction threshold below 4.5V:
In the USBH mode, the battery cell preconditioning or
trickle charge current is fixed at 10 percent of the programmed fast charge constant current. In the USBL mode,
the trickle charge current is only reduced to 50 percent of
the programmed fast charge constant current level.
where R1 and R2 < 1M
When the USBSEL pin is connected to a logic high level,
the USBH level will be active. Conversely, when USBSEL
is pulled to a logic low level (ground) the USBL level will
be used for fast charging. Refer to Table 2 for the recommended RUSBSET value to program the desired USB input
constant current charge levels.
Eq. 2: VUSBCHR =
VUSB
R1
2.0V
(R2/[R2 + R1])
USB
1.0M
CHRUSB
VCHR = 2.0V
R2
800k
USB Charge Reduction
In many instances, product system designers have an
issue of not knowing the real properties of a potential
USB port to be used to supply power to the battery charger. Typical powered USB ports commonly found on
desktop and notebook PCs should supply up to 500mA.
In the event a USB port being used to supply the charger
is unable to provide the programmed fast charge current, or if the system under charge must also share supply current with other functions causing an overload to
the USB port, the AAT3670 will automatically reduce
USB fast charge current to maintain port integrity and
protect the host system.
The USB charge reduction system becomes active when
the voltage on the USB input falls below the USB charge
reduction threshold (VCHRUSB), which is typically 4.5V.
Regardless of which USB charge function is selected
(USBH or USBL), the charge reduction system will
reduce the fast charge current level in a linear fashion
until the voltage sensed on the USB input recovers
above the charge reduction threshold voltage. The USB
charge reduction threshold (VCHRUSB) may be externally
set to a value lower than 4.5V by placing a resistor
divider network between VUSB and ground with the center connected to the CHRUSB pin. The USB charge
reduction feature may be disabled by shorting the
CHRUSB pin directly to the USB input pin.
Figure 4: Internal Equivalent Circuit for the
CHRUSB Pin.
USB Input Charge Inhibit and Resume
The AAT3670 under-voltage lockout (UVLO) and poweron reset feature will function when the USB input pin
voltage level drops below the UVLO threshold. At this
point the charger will suspend charging. When power is
re-applied to the USB 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.
End of Charge Termination
The AAT3670 provides a user-programmable charge termination current at the end of the charge cycles. When
the battery cell voltage as sensed by the BATS pin
reaches 4.2V, the charge control will transition from constant current fast charge mode to constant voltage
mode. In constant voltage mode, the battery cell voltage
will be regulated at 4.2V. The charge current will drop as
the battery reaches its full charge capacity. When the
charge current drops to the programmed end of charge
(EOC) current, the charge cycle is complete and the
charge controller terminates the charging process.
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21
DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
The charge termination current is user programmed by
the value of RTERM, which is connected between the TERM
pin and ground. Use the values listed in Table 1 to set
the desired charge termination current. The programmed
charge termination current will remain at the same set
level regardless of which fast charge ADP, USBH or USBL
constant current mode is selected.
ITERM (mA)
RTERM (kW)
320
174
125
95
77
64
58
50
49
42
37
11.0
21.0
30.9
41.2
51.1
61.9
71.5
80.6
90.9
100.0
110.0
Table 1: Charge Termination Current
Programming Resistor Values.
If the desired end of charge termination current level is
not listed in Table 1, the TERM resistor value may be
calculated by the following equation:
For the Adapter input mode:
RTERM = K ·
⎛ VTERM⎞
⎝ ICC ⎠
Where:
K = KI_TERM = 2000
VTERM = 2V
ICC = Fast charge constant current
The constants K and VTERM are specified in the Typical
Characteristics section of this datasheet.
The end-of-charge termination current function can be
disabled by pulling the TERM pin high via connecting the
TERM pin to the BAT pin. In this state, the end-of-charge
function will be disabled and the battery will float charge
in the constant voltage mode indefinitely or until the cell
voltage is brought below the constant voltage threshold.
22
System Power Output
The power to the system is supplied via the OUT pin. OUT
will source power from either the ADP or USB inputs when
an external power source is applied. When the battery
charging function is complete and the charging power
source is removed, the system will be powered from the
battery via Load Switch 3, referring to the AAT3670 block
diagram. The maximum current that can be supplied from
the ADP or USB inputs to a system load is bounded by the
user programmed ADPLIM and USBLIM level. If the current consumption from the system load exceeds that of
the ADP or USB input sources, the IC will draw current
from the battery to make up the difference as long as the
battery cell voltage remains above 2.9V. Power from the
battery to the OUT pin is controlled by the ENBAT function. When the ENBAT is disabled the leakage current
from the battery to the load is less than 1μA.
Battery Connection and
Battery Voltage Sensing
Battery Connection
The single cell Li-ion battery should be connected
between the BAT pin and ground. The internal load
switching network will connect the battery to the system
load and apply the charging current.
Battery Voltage Sensing
The BATS pin is provided to employ an accurate voltage
sensing capability to measure the terminal voltage at the
battery cell being charged. This function reduces measured battery cell voltage error between the battery
terminal and the charge control IC. The AAT3670 charge
control circuit will base charging mode states upon the
voltage sensed at the BATS pin. The BATS pin must be
connected to the battery terminal for correct operation.
If the battery voltage sense function is not needed, the
BATS pin should be terminated directly to the BAT pin. If
there is concern of the battery sense function inadvertently becoming an open circuit, the BATS pin may be
terminated to the BAT pin using a 10k resistor. Under
normal operation, the connection to the battery terminal
will be close to 0; if the BATS connection becomes an
open circuit, the 10k will provide feedback to the BATS
pin from the BAT connection will a 1mV or less loss in
sensed voltage accuracy.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
The AAT3670 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 AAT3670 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.
Battery Enable
Since the AAT3670 provides battery power switching as
well as charging function, a battery enable pin (ENBAT)
is provided so the power from the battery via the BAT
pin to the OUT pin may be externally controlled. The
ENBAT function allows the user to control power to the
systems regardless of charging state, input power
source, or charge enable (EN) state.
It may be desirable for some system designs to disconnect the battery from the load during charging. This may
be accomplished by pulling the ENBAT pin low, while the
device is enabled for charging (EN high).
Programming Charge Current
The fast charge constant current charge level for both
adapter and USB input modes are programmed with set
resistors placed between the ADPSET or USBSET pins
and ground. The accuracy of the fast charge constant
current and the preconditioning trickle charge current
are dominated by the tolerance of the set resistor used.
For this reason, 1% tolerance metal film resistors are
recommended for this set resistor function.
Fast charge constant current levels from 50mA to 1.6A
may be set by selecting the appropriate resistor value
from Table 2. The RADPSET resistor should be connected
between the ADPSET pin and ground.
The USB input fast charge constant current charge control provides up to 900mA of charge current and is set
in the USBH mode. The USBSEL pin is used to select the
high or low charge current levels in the USB charge
mode. When the USBSEL pin is pulled to a voltage level
above the VUSBSEL(H) threshold, the USBH current level will
be selected. Conversely, this pin should be pulled below
the VUSBSEL(L) threshold to enable the USBL charge level;
the USBL charge current will be set to 20% of the set
USBH level. For typical USB charging applications, the
USBH and USBL functions are fixed for 500mA and
100mA USB fast charge levels. However, the charge
level of USBH may be set from 50mA to 900mA and
USBL will in turn be fixed at 20% of the USBH level
depending upon the system design requirements for a
given USB charge application. Refer to Table 2 and
Figure 5 for recommended RUSBSET values.
ICC
(mA)
ADP
RSET (kW)
USBH
RSET (kW)
USBL
RSET (kW)
50
90
100
150
200
250
300
400
500
650
800
900
1000
1200
1500
1600
1300
681
590
412
309
249
205
154
121
93.1
73.2
64.9
57.6
48.7
38.3
34.8
750
453
383
249
187
150
124
90.9
71.5
54.9
43.2
38.3
150
80.6
71.5
47.5
34.8
Table 2: RSET Values.
1800
1600
IFASTCHARGE (mA)
Enable
1400
1200
USBH
1000
ADP
800
600
USBL
400
200
0
10
100
1000
10000
RSET (kΩ
Ω)
Figure 5: Fast Charge Current vs. Set Resistor
(VIN = 5V; VBAT = 3.5V).
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
If the desired current charge current level is not listed in
Table 2, the ADPSET and USBSET resistor values may be
calculated by the following equations:
For the Adapter input mode:
RADPSET = K ·
⎛ VADPSET⎞
⎝ ICC ⎠
Where:
K = KI_CCADP = 29300
VADPSET = 2V
ICC = Fast Charge Constant Current
For the USB input mode:
RUSBSET = K ·
⎛ VUSBSET⎞
⎝ ICC ⎠
Where:
K = KI_CCUSBH = 17900 (USBH)
K = KI_CCUSBL = 3600 (USBL)
VUSBSET = 2V
ICC = Fast Charge Constant Current
All constants K and VADP/USBSET are specified in the Typical
Characteristics section of this datasheet.
Protection Circuitry
Thermal Loop Control
Due to the integrated nature of the linear charging control pass devices for both the adapter and USB modes, a
special thermal loop control system has been employed
to maximize charging current under all operating conditions. The thermal management system measures the
internal circuit die temperature and reduces the charge
current when the device exceeds a preset internal temperature control threshold. Once the thermal loop control becomes active, the constant charge current is initially reduced by a factor of 0.44.
The initial thermal loop current can be estimated by the
following equations:
In ADP mode: ITLOOP = ICCADP · 0.44
In USB mode: ITLOOP = ICCUSBH · 0.44
24
The thermal loop control re-evaluates the internal die
temperature every three seconds and adjusts the fast
charge current back up in small steps up to the full fast
charge current level or until an equilibrium current is
discovered and maximized for the given ambient temperature condition. In this manner, the thermal loop
controls the system charge level. The AAT3670 will
always provide the highest possible level of constant current in the fast charge mode for any given ambient temperature condition.
Programmable Watchdog Timer
The AAT3670 contains a watchdog timing circuit which
operates only in adapter charging mode. 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 a shutdown condition if the trickle
charge mode exceeds 45 minutes. When the device transitions to the trickle charge to the fast charge constant
current mode and then to the constant voltage mode,
the timing counter is reset and will time out after 3 hours
for each mode.
Summary for a 0.1μF used for the timing capacitor:
Trickle Charge (TC) time out = 45 minutes
Fast Charge Constant Current (CC) time out = 3 hours
Constant Voltage (VC) mode time out = 3 hours
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 time
of the CC + CV modes would be doubled. The corresponding trickle charge time out time would be the combined CC + VC time divided by 8.
If the programmable watchdog timer function is not
needed it may be disabled the terminating the CT pin to
ground. The CT pin should not be left floating or unterminated; this will cause errors in the internal timing
control circuit.
The charge timer control will suspend the timing count in
any given mode in the event a fault condition occurs.
Such fault conditions include digital thermal loop charge
current reduction, ADP or USB charge reduction, battery
temperature fault, and battery current sharing with the
output during the charging cycle. When the fault condition recovers, the counter will resume the timing function. The charge timer will automatically reset when the
AAT3670 enable pin is reset or cycled off and on.
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
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 determined by the capacitance value, a 10% tolerance or
better ceramic capacitor is recommended. Ceramic
capacitor materials such as X7R and X5R type are a
good choice for this application.
If the desired charge current limit level is not listed in
Table 3, the ADPLIM and USBLIM set resistor values may
be calculated by the following equations:
Over-Current Protection
K = KI_LIM_ADP = 27800
VADPLIM = 2V
ICC = Fast Charge Constant Current
The AAT3670 provides over-current protection to both
the battery and system output modes for both the ADP
and USB input sources.
The over-current protection threshold is user programmable and independent from the constant charge current
setting. The set resistor RADPLIM is connected between the
ADPLIM pin and ground to program the ADP power path
current limit up to 1.6A. The set resistor RUSBLIM is connected between the USBLIM pin and ground to program
the USB power path current limit up to 900mA. For both
the ADP and USB charge paths, the programmed constant
current fast charge level may not exceed the respective
ADPLIM and USBLIM set points. Refer to Table 3 for the
ADPLIM and USBLIM programming resistor values.
ICC (mA)
RADPLIM (kW)
RUSBLIM (kW)
50
90
100
150
200
250
300
400
500
650
800
900
1000
1200
1500
1600
1300
681
590
412
309
249
205
154
121
93.1
73.2
64.9
57.6
48.7
38.3
34.8
750
453
383
249
187
150
124
90.9
71.5
54.9
43.2
38.3
Table 3: Current Limit Programming
Resistor Values.
For the Adapter input mode:
RADPLIM = K ·
⎛ VADPLIM⎞
⎝ ICC ⎠
Where:
For the USB input mode:
RUSBLIM = K ·
⎛ VUSBLIM⎞
⎝ ICC ⎠
Where:
K = KI_LIM_USBH = 17600 (USBH)
K = KI_LIM_USBL = 3500 (USBL)
VUSBLIM = 2V
ICC = Fast Charge Constant Current
All constants K and VADP/USBLIM are specified in the Typical
Characteristics section of this datasheet.
Over-Voltage Protection
An over-voltage event is defined as a condition where
the voltage on the BATS pin exceeds the maximum battery charge voltage and is set by the over-voltage protection threshold (VOVP). If an over-voltage condition
occurs, the AAT3670 charge control will shutdown the
device until voltage on the BATS pin drops below the
over-voltage protection threshold (VOVP). The AAT3670
will resume normal charging operation once the battery
over-voltage condition is removed. During an over-voltage event, the STAT2 LED will report a system fault.
Over-Temperature Shutdown
The AAT3670 has a thermal protection control circuit
which will shut down charging functions should the internal die temperature exceed the preset thermal limit
threshold.
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25
DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Battery Temperature Fault Monitoring
Status Indicator Display
In the event of a battery over-temperature condition, the
charge control will turn off the internal charge path regulation device and report the fault condition via the STAT2
display LED. After the system recovers from a temperature fault, the device will resume charging operation. The
AAT3670 checks battery temperature before starting the
charge cycle, as well as during all stages of charging.
System charging status may be displayed using one or
two LEDs in conjunction with the STAT1 and STAT2 pins
on the AAT3670. These two pins are simple switches to
connect the status 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 for the various charging
states. Refer to Table 4 for LED display definitions.
Typically, batteries employ the use of a negative temperature coefficient (NTC) thermistor that is integrated
into the battery package. Most commonly used NTC
thermistors used in battery packs are approximately
10k at room temperature (25°C). However, the
AAT3670 TS pin, in conjunction with the VTS pin, permits
the use of almost any value of NTC thermistor.
There are two pins associated with the battery temperature sensing function, TS and VTS. The battery pack
thermistor should be connected between the TS pin and
ground. The VTS pin is provided to allow the user to
program battery temperature sense thresholds depending upon the value of the NTC thermistor used in a given
battery pack. A resistor (RT) connected between the VTS
pin and the TS pin will set a bias for the NTC thermistor
function. The TS function has been designed such that a
default NTC thermistor value of 10k will then require a
10k resistor for RT. To determine the actual operating
temperature window for the the NTC thermistor and the
TS pin, one must first specify the NTC thermistor to be
used, then refer to the thermistor datasheet to determine its characteristics.
The internal battery temperature sensing system is comprised of two comparators which establish a voltage
window for safe operation. The thresholds for the TS
operating window are bounded by the TS1 and TS2
specifications. Referring to the electrical characteristics
table in this datasheet, the TS1 threshold = 0.30 · VVTS
and the TS2 threshold = 0.72 · VVTS. The VTS pin is
capable of sourcing up to 2mA.
If the use of the battery temperature sense function is
not required, it may be disabled by disconnecting the
VTS pin from the TS pin and terminating the TS pin to
ground. The VTS pin can be left floating.
VTS
0.72 · VVTS
RT
TS
Battery Cold Fault
+
RNTC
Battery Hot Fault
T
+
0.30 · VVTS
Figure 6: Battery Temperature Sense Circuit.
VTS
RT
0.72V
Battery Cold Fault
TS
+
RADJ
0.30V
RNTC
Battery Hot Fault
+
T
Battery Charge Status Indication
The AAT3670 indicates the status of the battery under
charge using two status LED driver outputs. These two
LEDs can indicate simple functions such as no battery
charge activity, battery charging, charge complete and
charge fault.
26
Figure 7: Battery Temperature Sense Circuit with
Externally Adjusted Window Threshold.
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Event Description
STAT1
End of Charge (TERM Current Reached in CVM), Battery OV, Timeout, or Charge Disabled
No Battery (With Charge Enabled)
Battery Charging (Including Suspended Charging Due to Battery OT/UT, or Device OT )
OFF
Flash (1Hz, 40% duty)
ON
Event Description
STAT2
Charge Disabled, No Battery, End of Charge, or Charging Without Faults
Faults (Battery OV/OT/UT, or Device OT) or Timeout
OFF
ON
Table 4: LED Status Indicator (STATx Pulled Up to a Voltage Source with Resistors and LED).
The LED anodes should be connected to USB, ADP, BAT,
or OUT depending upon the system design requirements. The LEDs should be biased with as little current
as necessary to create reasonable illumination. A ballast
resistor should be placed between the status LED cathodes and the STAT1/2 pins. LED current consumption
will add to the over thermal power budget for the device
package, hence it is good reason to keep the LED drive
current to a minimum. 2mA should be sufficient to drive
most common low cost green or red LEDs. It is not recommended to exceed 8mA for driving an individual status LED. The required ballast resistor value can be estimated using the following formulas:
For connection to the adapter supply:
Eq. 3: RB(STAT1/2) =
(VADP - VF(LED))
ILED(STAT1/2)
Example: RB(STAT2) = (3.6V - 3.2V) 2mA = 200
Note: Green LED forward voltage (VF) is typically 3.2V @
2mA.
No Battery Present Indication
If the AAT3670 charger IC is powered and enabled from
either the ADP or USB input, yet no battery is connected
to the BAT and BATS pins, the STAT1 LED will flash at a
1Hz rate with an approximate 40% duty cycle when a
10μF capacitor is connected between the BAT pin and
ground. The flash rate of the STAT1 LED can be adjusted
by changing the value of the battery output (BAT pin)
capacitor. If the capacitor value is increased above 20μF,
the no battery detect flashing function will be defeated.
The flash rate of the no battery detect function may be
approximated by the following equation:
Example: RB(STAT1) = (5.5V - 2.0V) 2mA = 1.75k
Note: Red LED forward voltage (VF) is typically 2.0V @
2mA.
For connection to the USB supply:
Eq. 4: RB(STAT1/2) =
(VUSB - VF(LED))
ILED(STAT1/2)
Example: RB(STAT2) = (5.0V - 3.2V) 2mA = 900
Note: Green LED forward voltage (VF) is typically 3.2V @
2mA.
For connection to the BAT supply:
Eq. 5: RB(STAT1/2) =
(VBAT - VF(LED))
ILED(STAT1/2)
Eq. 6: C =
I ·T
V
Where:
C = Capacitor value
I = Start up source current from the BAT pin = 5μA
V = Difference voltage between the end of charge voltage and the battery recharge threshold = 0.2V
T = Rate of LED flashing in seconds
Thermal Considerations
The AAT3670 is available in a 4x4mm 24-pin QFN package which can provide up to 2.0W of power dissipation
when it is properly bonded to a printed circuit board, but
can achieve a maximum thermal resistance of 37°C/W
with printed circuit board enhancement. Many considerations 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 ambi-
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27
DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
ent temperature around the charger IC will also have an
effect on the thermal limits of a battery charging application. The maximum limits that can be expected for a
given ambient condition can be estimated by the following discussion:
First, the maximum power dissipation for a given situation should the calculated:
Eq. 7: PD = [(VIN - VBAT) · ICC + (VIN · IOP) + (IOUT2 · RDS(ON))
Given:
VADP = 5.0V
VBAT = 3.0V
ICC = 1A
IOP = 0.75mA
TJ = 110°C
JA = 37°C/W
IOUT = 0
RDS(ON) = 0.4
Using Equation 7, calculate the device power dissipation
for the stated condition:
Where:
PD
VIN
VBAT
ICC
IOP
IOUT
RDS(ON)
= Total power dissipation by the device
= either VADP or VUSB, depending on which mode is
selected
= Battery voltage as seen at the BAT pin
= Maximum constant fast charge current programmed for the application
= Quiescent current consumed by the charger IC
for normal operation
= Load current to system from the OUT pin
= On-resistance of load switch between ADP or
USB and OUT
Next, the maximum operating ambient temperature for
a given application can be estimated based on the thermal resistance of the 4x4 QFN package when sufficiently
mounted to a PCB layout and the internal thermal loop
temperature threshold.
Eq. 8: TA = TJ - (θJA · PD)
= 2.00375W
The maximum ambient temperature before the AAT3670
thermal loop becomes active can now be calculated
using Equation 8:
Eq. 10: TA = 110°C - (37°C/W · 2.00375W)
= 35.86°C
Therefore, under the stated conditions for this worstcase power dissipation example, the AAT3670 will enter
the thermal loop and lower the fast charge constant current when the ambient operating temperature rises
above 35.86°C.
Capacitor Selection
Input Capacitor
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 worstcase battery voltage at 3.0V with the system load disabled, what is the maximum ambient temperature where
the thermal limiting will become active?
28
Eq. 9: PD = (5.0V - 3.0V)(1A) + (5.0V · 0.75mA) + (02 · 0.4Ω)
In general, it is good design practice to place a decoupling
capacitor between the ADP and USB pins and ground. An
input capacitor in the range of 1μF to 22μF is recommended. 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 AAT3670 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 bounce effects
when the power supply is “hot plugged” in. Likewise, a
10μF or greater input capacitor is recommended for the
USB input to help buffer the effects of USB source power
switching, noise and input cable impedance.
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Printed Circuit Board
Layout Considerations
Output Capacitor
The AAT3670 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 AAT3670 is to be used in applications where the battery can be removed from the charger, such as with the
case with desktop charging cradles, an output capacitor
greater than 10μF, but less than 20μF, may be required
to retard the device from cycling on and off when no
battery is present.
J6
For the best results, it is recommended to physically place
the battery pack as close as possible to the AAT3670 BAT
pin as possible. To minimize voltage drops on the PCB,
keep the high current carrying traces adequately wide.
For maximum power dissipation of the AAT3670 QFN
package, the metal substrate should be solder bonded to
the board. It is also recommended to maximize the substrate contact to the PCB ground plane layer to further
increase local heat dissipation. Refer to the AAT3670
evaluation board for a good layout example.
J2
J8
USB
USB
2 1
USBSEL
1 2 3 4 5
R131
D1
1 2 3
R121
D2
R11
R10
1k
1k
C2
10μF
D3A
SOT-23
J1
1
2
3
D3B
CT
ADP
STAT2
N/C
STAT1
USB
ENBAT
18
EN
17
R9
OUT
TERM
4
BAT
GND
15
5
BAT
USBSET
14
R8
ADPSET
13
71.5k
R7
ADP
AAT3670
7
8
9
10
11
ENBAT
J3
16
VTS
C1
10μF
CT
C4
0.01μF
3
6
BAT
J4
1
2
OUT
19
USBLIM
C3
10μF
USBSEL
2
20
ADPLIM
1
2
3
1
21
CHRADP
OUT
J5
C5
10μF
22
BATS
1
2
23
TS
J7
24
CHRUSB
U1
71.5k
1
2
3
ENABLE
57.6k
12
R1
100k
R2
100k
R31
R41
R5
R6
34.8k 39.2k
TS
Figure 8: AAT3670 Evaluation Board Schematic.
1. Not populated (Open) on the Evaluation Board
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DATA SHEET
AAT3670
1.6A Dynamic Battery Charger and Power Manager
Figure 9: AAT3670 Evaluation Board Top Side Layout.
Figure 10: AAT3670 Evaluation Board Bottom Side Layout.
30
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DATA
DATA SHEET
SHEET
AAT3670
1.6A Dynamic
Dynamic Battery
Battery Charger
Charger and
and Power
Power Manager
Manager
1.6A
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
QFN44-24
TFXYY
AAT3670ISK-4.2-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
QFN44-24
0.4 ± 0.05
24
1
2.7 ± 0.05
0.5 BSC
R0.030Max
13
6
12
4.000 ± 0.050
7
2.7 ± 0.05
Top View
0.025 ± 0.025
Bottom View
0.214 ± 0.036
0.900 ± 0.050
4.000 ± 0.050
19
18
0.300 ´ 45°
Pin 1 Identification
0.305 ± 0.075
Pin 1 Dot By Marking
Side View
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.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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